Network Working Group S. Dusse
Request for Comments: 2311 RSA Data Security
Category: Informational P. Hoffman
Internet Mail Consortium
B. Ramsdell
Worldtalk
L. Lundblade
Qualcomm
L. Repka
Netscape
March 1998
Network Working Group S. Dusse
Request for Comments: 2311 RSA Data Security
Category: Informational P. Hoffman
Internet Mail Consortium
B. Ramsdell
Worldtalk
L. Lundblade
Qualcomm
L. Repka
Netscape
March 1998
S/MIME Version 2 Message Specification
S/MIME版本2消息规范
Status of this Memo
本备忘录的状况
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
本备忘录为互联网社区提供信息。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (1998). All Rights Reserved.
版权所有（C）互联网协会（1998年）。版权所有。
S/MIME (Secure/Multipurpose Internet Mail Extensions) provides a consistent way to send and receive secure MIME data. Based on the popular Internet MIME standard, S/MIME provides the following cryptographic security services for electronic messaging applications: authentication, message integrity and non-repudiation of origin (using digital signatures) and privacy and data security (using encryption).
S/MIME（安全/多用途Internet邮件扩展）提供了发送和接收安全MIME数据的一致方式。基于流行的Internet MIME标准，S/MIME为电子消息应用程序提供以下加密安全服务：身份验证、消息完整性和来源不可否认性（使用数字签名）以及隐私和数据安全（使用加密）。
S/MIME can be used by traditional mail user agents (MUAs) to add cryptographic security services to mail that is sent, and to interpret cryptographic security services in mail that is received. However, S/MIME is not restricted to mail; it can be used with any transport mechanism that transports MIME data, such as HTTP. As such, S/MIME takes advantage of the object-based features of MIME and allows secure messages to be exchanged in mixed-transport systems.
传统的邮件用户代理（MUA）可以使用S/MIME向发送的邮件添加加密安全服务，并解释接收的邮件中的加密安全服务。但是，S/MIME不限于邮件；它可以用于传输MIME数据的任何传输机制，如HTTP。因此，S/MIME利用了MIME基于对象的特性，并允许在混合传输系统中交换安全消息。
Further, S/MIME can be used in automated message transfer agents that use cryptographic security services that do not require any human intervention, such as the signing of software-generated documents and the encryption of FAX messages sent over the Internet.
此外，S/MIME可用于自动消息传输代理，该代理使用不需要任何人工干预的加密安全服务，例如软件生成文档的签名和通过Internet发送的传真消息的加密。
Please note: The information in this document is historical material being published for the public record. It is not an IETF standard. The use of the word "standard" in this document indicates a standard for adopters of S/MIME version 2, not an IETF standard.
请注意：本文件中的信息是公开记录的历史资料。它不是IETF标准。本文件中使用“标准”一词表示S/MIME版本2采用者的标准，而不是IETF标准。
This document describes a protocol for adding cryptographic signature and encryption services to MIME data. The MIME standard [MIME-SPEC] provides a general structure for the content type of Internet messages and allows extensions for new content type applications.
本文档描述了向MIME数据添加加密签名和加密服务的协议。MIME标准[MIME-SPEC]为Internet消息的内容类型提供了通用结构，并允许扩展新的内容类型应用程序。
This memo defines how to create a MIME body part that has been cryptographically enhanced according to PKCS #7 [PKCS-7]. This memo also defines the application/pkcs7-mime MIME type that can be used to transport those body parts. This memo also defines how to create certification requests that conform to PKCS #10 [PKCS-10], and the application/pkcs10 MIME type for transporting those requests.
本备忘录定义了如何创建已根据PKCS#7[PKCS-7]进行加密增强的MIME主体部分。此备忘录还定义了可用于传输这些身体部位的application/pkcs7 mime mime类型。本备忘录还定义了如何创建符合PKCS#10[PKCS-10]的认证请求，以及用于传输这些请求的应用程序/pkcs10 MIME类型。
This memo also discusses how to use the multipart/signed MIME type defined in [MIME-SECURE] to transport S/MIME signed messages. This memo also defines the application/pkcs7-signature MIME type, which is also used to transport S/MIME signed messages. This specification is compatible with PKCS #7 in that it uses the data types defined by PKCS #7.
本备忘录还讨论了如何使用[MIME-SECURE]中定义的多部分/签名MIME类型来传输S/MIME签名消息。此备忘录还定义了application/pkcs7签名MIME类型，该类型也用于传输S/MIME签名消息。本规范与PKCS#7兼容，因为它使用PKCS#7定义的数据类型。
In order to create S/MIME messages, an agent has to follow specifications in this memo, as well as some of the specifications listed in the following documents:
为了创建S/MIME消息，代理必须遵循本备忘录中的规范以及以下文档中列出的一些规范：
- "PKCS #1: RSA Encryption", [PKCS-1]
- "PKCS #7: Cryptographic Message Syntax", [PKCS-7]
- "PKCS #10: Certification Request Syntax", [PKCS-10]
- "PKCS #1: RSA Encryption", [PKCS-1]
- "PKCS #7: Cryptographic Message Syntax", [PKCS-7]
- "PKCS #10: Certification Request Syntax", [PKCS-10]
Throughout this memo, there are requirements and recommendations made for how receiving agents handle incoming messages. There are separate requirements and recommendations for how sending agents create outgoing messages. In general, the best strategy is to "be liberal in what you receive and conservative in what you send". Most of the requirements are placed on the handling of incoming messages while the recommendations are mostly on the creation of outgoing messages.
在本备忘录中，有关于接收代理如何处理传入消息的要求和建议。对于发送代理如何创建传出消息，有单独的要求和建议。总的来说，最好的策略是“在你收到的东西上自由，在你发送的东西上保守”。大多数需求放在传入消息的处理上，而建议主要放在传出消息的创建上。
The separation for requirements on receiving agents and sending agents also derives from the likelihood that there will be S/MIME systems that involve software other than traditional Internet mail clients. S/MIME can be used with any system that transports MIME
对接收代理和发送代理的要求的分离还源于可能存在S/MIME系统，这些系统涉及传统Internet邮件客户端以外的软件。S/MIME可用于传输MIME的任何系统
data. An automated process that sends an encrypted message might not be able to receive an encrypted message at all, for example. Thus, the requirements and recommendations for the two types of agents are listed separately when appropriate.
数据例如，发送加密消息的自动化进程可能根本无法接收加密消息。因此，在适当的情况下，将分别列出这两类代理的要求和建议。
Throughout this memo, the terms MUST, MUST NOT, SHOULD, and SHOULD NOT are used in capital letters. This conforms to the definitions in [MUSTSHOULD]. [MUSTSHOULD] defines the use of these key words to help make the intent of standards track documents as clear as possible. The same key words are used in this document to help implementors achieve interoperability.
在本备忘录中，术语必须、不得、应当和不应当以大写字母使用。这符合[必须]中的定义。[MUSTSHOULD]定义这些关键词的用法，以帮助尽可能清楚地表达标准跟踪文件的意图。本文档中使用了相同的关键词来帮助实现者实现互操作性。
For the purposes of this memo, the following definitions apply.
在本备忘录中，以下定义适用。
ASN.1: Abstract Syntax Notation One, as defined in CCITT X.208.
ASN.1：抽象语法符号1，如CCITT X.208中所定义。
BER: Basic Encoding Rules for ASN.1, as defined in CCITT X.209.
BER：ASN.1的基本编码规则，如CCITT X.209中所定义。
Certificate: A type that binds an entity's distinguished name to a public key with a digital signature.
证书：用数字签名将实体的可分辨名称绑定到公钥的类型。
DER: Distinguished Encoding Rules for ASN.1, as defined in CCITT X.509.
DER：ASN.1的特殊编码规则，如CCITT X.509中所定义。
7-bit data: Text data with lines less than 998 characters long, where none of the characters have the 8th bit set, and there are no NULL characters. <CR> and <LF> occur only as part of a <CR><LF> end of line delimiter.
7位数据：行长度小于998个字符的文本数据，其中没有字符设置为第8位，也没有空字符<CR>和<LF>仅作为<CR><LF>行尾分隔符的一部分出现。
8-bit data: Text data with lines less than 998 characters, and where none of the characters are NULL characters. <CR> and <LF> occur only as part of a <CR><LF> end of line delimiter.
8位数据：行数小于998个字符的文本数据，其中所有字符都不是空字符<CR>和<LF>仅作为<CR><LF>行尾分隔符的一部分出现。
Binary data: Arbitrary data.
二进制数据：任意数据。
Transfer Encoding: A reversible transformation made on data so 8-bit or binary data may be sent via a channel that only transmits 7-bit data.
传输编码：对数据进行的可逆转换，因此8位或二进制数据可以通过仅传输7位数据的通道发送。
Appendix C contains important information about how S/MIME agents following this specification should act in order to have the greatest interoperability with earlier implementations of S/MIME.
附录C包含有关遵循本规范的S/MIME代理应如何操作的重要信息，以便与早期的S/MIME实现具有最大的互操作性。
The PKCS #7 message format allows for a wide variety of options in content and algorithm support. This section puts forth a number of support requirements and recommendations in order to achieve a base level of interoperability among all S/MIME implementations.
PKCS#7消息格式允许在内容和算法支持方面提供多种选择。本节提出了一些支持需求和建议，以实现所有S/MIME实现之间的基本互操作性。
Receiving agents MUST support SHA-1 [SHA1] and MD5 [MD5].
接收代理必须支持SHA-1[SHA1]和MD5[MD5]。
Sending agents SHOULD use SHA-1.
发送代理应使用SHA-1。
Receiving agents MUST support rsaEncryption, defined in [PKCS-1]. Receiving agents MUST support verification of signatures using RSA public key sizes from 512 bits to 1024 bits.
接收代理必须支持[PKCS-1]中定义的RSA加密。接收代理必须支持使用RSA公钥大小从512位到1024位的签名验证。
Sending agents MUST support rsaEncryption. Outgoing messages are signed with a user's private key. The size of the private key is determined during key generation.
发送代理必须支持RSA加密。传出消息使用用户的私钥签名。私钥的大小在密钥生成期间确定。
Receiving agents MUST support rsaEncryption. Incoming encrypted messages contain symmetric keys which are to be decrypted with a user's private key. The size of the private key is determined during key generation.
接收代理必须支持RSA加密。传入的加密消息包含对称密钥，这些密钥将使用用户的私钥解密。私钥的大小在密钥生成期间确定。
Sending agents MUST support rsaEncryption. Sending agents MUST support encryption of symmetric keys with RSA public keys at key sizes from 512 bits to 1024 bits.
发送代理必须支持RSA加密。发送代理必须支持使用RSA公钥加密对称密钥，密钥大小从512位到1024位。
The PKCS #7 defines six distinct content types: "data", "signedData", "envelopedData", "signedAndEnvelopedData", "digestedData", and "encryptedData". Receiving agents MUST support the "data", "signedData" and "envelopedData" content types. Sending agents may or may not send out any of the content types, depending on the services that the agent supports.
PKCS#7定义了六种不同的内容类型：“数据”、“签名数据”、“信封数据”、“签名和开发数据”、“摘要数据”和“加密数据”。接收代理必须支持“数据”、“签名数据”和“信封数据”内容类型。发送代理可以发送也可以不发送任何内容类型，具体取决于代理支持的服务。
Sending agents MUST use the "data" content type as the content within other content types to indicate the message content which has had security services applied to it.
发送代理必须使用“数据”内容类型作为其他内容类型中的内容，以指示已应用安全服务的邮件内容。
Sending agents MUST use the signedData content type to apply a digital signature to a message or, in a degenerate case where there is no signature information, to convey certificates.
发送代理必须使用signedData内容类型对消息应用数字签名，或者在没有签名信息的退化情况下传递证书。
This content type is used to apply privacy protection to a message. A sender needs to have access to a public key for each intended message recipient to use this service. This content type does not provide authentication.
此内容类型用于对邮件应用隐私保护。要使用此服务，发件人需要访问每个预期邮件收件人的公钥。此内容类型不提供身份验证。
The SignerInfo type allows the inclusion of unauthenticated and authenticated attributes to be included along with a signature.
SignerInfo类型允许将未经身份验证和身份验证的属性与签名一起包含。
Receiving agents MUST be able to handle zero or one instance of each of the signed attributes described in this section.
接收代理必须能够处理本节中描述的每个签名属性的零个或一个实例。
Sending agents SHOULD be able to generate one instance of each of the signed attributes described in this section, and SHOULD include these attributes in each signed message sent.
发送代理应该能够生成本节中描述的每个签名属性的一个实例，并且应该在发送的每个签名消息中包含这些属性。
Additional attributes and values for these attributes may be defined in the future. Receiving agents SHOULD handle attributes or values that it does not recognize in a graceful manner.
将来可能会定义这些属性的其他属性和值。接收代理应该以优雅的方式处理它无法识别的属性或值。
The signing-time attribute is used to convey the time that a message was signed. Until there are trusted timestamping services, the time of signing will most likely be created by a message originator and therefore is only as trustworthy as the originator.
签名时间属性用于传递消息签名的时间。在有可信的时间戳服务之前，签名时间最有可能由消息发起者创建，因此只与发起者一样可信。
Sending agents MUST encode signing time through the year 2049 as UTCTime; signing times in 2050 or later MUST be encoded as GeneralizedTime. Agents MUST interpret the year field (YY) as follows: if YY is greater than or equal to 50, the year is interpreted as 19YY; if YY is less than 50, the year is interpreted as 20YY.
发送代理必须将2049年的签名时间编码为UTCTime；2050年或以后的签名时间必须编码为GeneralizedTime。代理商必须将年份字段（YY）解释为：如果YY大于或等于50，则年份解释为19YY；如果YY小于50，则年份被解释为20YY。
The S/MIME capabilities attribute includes signature algorithms (such as "md5WithRSAEncryption"), symmetric algorithms (such as "DES-CBC"), and key encipherment algorithms (such as "rsaEncryption"). It also
S/MIME capabilities属性包括签名算法（如“md5WithRSAEncryption”）、对称算法（如“DES-CBC”）和密钥加密算法（如“rsaEncryption”）。它也
includes a non-algorithm capability which is the preference for signedData. SMIMECapabilities was designed to be flexible and extensible so that, in the future, a means of identifying other capabilities and preferences such as certificates can be added in a way that will not cause current clients to break.
包括非算法功能，这是signedData的首选功能。SMIMECapabilities的设计是灵活和可扩展的，以便将来可以以不会导致当前客户端中断的方式添加一种识别其他功能和首选项（如证书）的方法。
The semantics of the S/MIME capabilites attribute specify a partial list as to what the client announcing the SMIMECapabilites can support. A client does not have to list every capability it supports, and probably should not list all its capabilities so that the capabilities list doesn't get too long. In an SMIMECapabilities encoding, the OIDs are listed in order of their preference, but SHOULD be logically separated along the lines of their categories (signature algorithms, symmetric algorithms, key encipherment algorithms, etc.)
S/MIME capabilites属性的语义指定了一个部分列表，其中列出了宣布SMIMECapabilites的客户端可以支持的内容。客户机不必列出它支持的所有功能，而且可能不应该列出它的所有功能，这样功能列表就不会太长。在SMIMECapabilities编码中，OID按其偏好顺序列出，但应按照其类别（签名算法、对称算法、密钥加密算法等）进行逻辑分隔
The structure of SMIMECapabilities was designed to facilitate simple table lookups and binary comparisons in order to determine matches. For instance, the DER-encoding for the SMIMECapability for DES EDE3 CBC MUST be identically encoded regardless of the implementation.
SMIMECapabilities的结构旨在方便简单的表查找和二进制比较，以确定匹配。例如，DES EDE3 CBC的SMIMECapability的DER编码必须是相同的编码，而与实现无关。
In the case of symmetric algorithms, the associated parameters for the OID MUST specify all of the parameters necessary to differentiate between two instances of the same algorithm. For instance, the number of rounds and block size for RC5 must be specified in addition to the key length.
对于对称算法，OID的关联参数必须指定区分同一算法的两个实例所需的所有参数。例如，除了密钥长度外，还必须指定RC5的轮数和块大小。
There is a list of OIDs (the registered SMIMECapability list) that is centrally maintained and is separate from this memo. The list of OIDs is maintained by the Internet Mail Consortium at <http://www.imc.org/ietf-smime/oids.html>.
有一个集中维护的OID列表（注册的SMIMECapability列表），与本备忘录分开。OID列表由Internet Mail Consortium保存在<http://www.imc.org/ietf-smime/oids.html>.
The OIDs that correspond to algorithms SHOULD use the same OID as the actual algorithm, except in the case where the algorithm usage is ambiguous from the OID. For instance, in an earlier memo, rsaEncryption was ambiguous because it could refer to either a signature algorithm or a key encipherment algorithm. In the event that an OID is ambiguous, it needs to be arbitrated by the maintainer of the registered S/MIME capabilities list as to which type of algorithm will use the OID, and a new OID MUST be allocated under the smimeCapabilities OID to satisfy the other use of the OID.
与算法对应的OID应使用与实际算法相同的OID，除非算法用法与OID不明确。例如，在之前的一份备忘录中，RSA加密是不明确的，因为它可以引用签名算法或密钥加密算法。如果OID不明确，则需要由已注册S/MIME能力列表的维护者仲裁哪种类型的算法将使用OID，并且必须在smimeCapabilities OID下分配新的OID以满足OID的其他用途。
The registered S/MIME capabilities list specifies the parameters for OIDs that need them, most notably key lengths in the case of variable-length symmetric ciphers. In the event that there are no differentiating parameters for a particular OID, the parameters MUST be omitted, and MUST NOT be encoded as NULL.
注册的S/MIME功能列表指定了需要它们的OID的参数，尤其是可变长度对称密码的密钥长度。如果特定OID没有区分参数，则必须忽略这些参数，并且不得将其编码为NULL。
Additional values for SMIMECapability may be defined in the future. Receiving agents MUST handle a SMIMECapabilities object that has values that it does not recognize in a graceful manner.
将来可能会定义SMIMECapability的其他值。接收代理必须处理SMIMECapabilities对象，该对象的值不能被优雅地识别。
Receiving agents MUST support decryption using the RC2 [RC2] or a compatible algorithm at a key size of 40 bits, hereinafter called "RC2/40". Receiving agents SHOULD support decryption using DES EDE3 CBC, hereinafter called "tripleDES" [3DES] [DES].
接收代理必须支持使用RC2[RC2]或密钥大小为40位的兼容算法（以下称为“RC2/40”）进行解密。接收代理应支持使用DES EDE3 CBC（以下称为“tripleDES”[3DES][DES]进行解密。
Sending agents SHOULD support encryption with RC2/40 and tripleDES.
发送代理应支持使用RC2/40和三重加密。
When a sending agent creates an encrypted message, it has to decide which type of encryption to use. The decision process involves using information garnered from the capabilities lists included in messages received from the recipient, as well as out-of-band information such as private agreements, user preferences, legal restrictions, and so on.
当发送代理创建加密消息时，它必须决定使用哪种加密类型。决策过程涉及使用从收件人收到的消息中包含的功能列表中收集的信息，以及带外信息，如私人协议、用户首选项、法律限制等。
Section 2.5 defines a method by which a sending agent can optionally announce, among other things, its decrypting capabilities in its order of preference. The following method for processing and remembering the encryption capabilities attribute in incoming signed messages SHOULD be used.
第2.5节定义了一种方法，通过该方法，发送代理可以选择按其优先顺序宣布其解密能力。应使用以下方法来处理和记住传入签名消息中的加密功能属性。
- If the receiving agent has not yet created a list of capabilities for the sender's public key, then, after verifying the signature on the incoming message and checking the timestamp, the receiving agent SHOULD create a new list containing at least the signing time and the symmetric capabilities.
- 如果接收代理尚未为发送方的公钥创建功能列表，则在验证传入消息上的签名并检查时间戳后，接收代理应创建一个至少包含签名时间和对称功能的新列表。
- If such a list already exists, the receiving agent SHOULD verify that the signing time in the incoming message is greater than the signing time stored in the list and that the signature is valid. If so, the receiving agent SHOULD update both the signing time and capabilities in the list. Values of the signing time that lie far in the future (that is, a greater discrepancy than any reasonable clock skew), or a capabilitie lists in messages whose signature could not be verified, MUST NOT be accepted.
- 如果此类列表已经存在，则接收代理应验证传入消息中的签名时间是否大于列表中存储的签名时间，以及签名是否有效。如果是这样，接收代理应该更新列表中的签名时间和功能。不能接受未来很长时间内的签名时间值（即，比任何合理的时钟偏差都大的差异）或无法验证签名的消息中的能力列表。
The list of capabilities SHOULD be stored for future use in creating messages.
应存储功能列表，以便将来在创建消息时使用。
Before sending a message, the sending agent MUST decide whether it is willing to use weak encryption for the particular data in the
在发送消息之前，发送代理必须决定是否愿意对消息中的特定数据使用弱加密
message. If the sending agent decides that weak encryption is unacceptable for this data, then the sending agent MUST NOT use a weak algorithm such as RC2/40. The decision to use or not use weak encryption overrides any other decision in this section about which encryption algorithm to use.
消息如果发送代理决定此数据不能接受弱加密，则发送代理不得使用弱算法，如RC2/40。使用或不使用弱加密的决定将覆盖本节中有关使用哪种加密算法的任何其他决定。
Sections 2.6.2.1 through 2.6.2.4 describe the decisions a sending agent SHOULD use in deciding which type of encryption should be applied to a message. These rules are ordered, so the sending agent SHOULD make its decision in the order given.
第2.6.2.1节至第2.6.2.4节描述了发送代理在决定对消息应用哪种类型的加密时应使用的决定。这些规则是有序的，因此发送代理应该按照给定的顺序做出决定。
If the sending agent has received a set of capabilities from the recipient for the message the agent is about to encrypt, then the sending agent SHOULD use that information by selecting the first capability in the list (that is, the capability most preferred by the intended recipient) for which the sending agent knows how to encrypt. The sending agent SHOULD use one of the capabilities in the list if the agent reasonably expects the recipient to be able to decrypt the message.
如果发送代理已从收件人处收到一组代理将要加密的消息的功能，则发送代理应通过选择列表中发送代理知道如何加密的第一个功能（即预期收件人最喜欢的功能）来使用该信息。如果发送代理合理地期望收件人能够解密邮件，则发送代理应使用列表中的功能之一。
If: - the sending agent has no knowledge of the encryption capabilities of the recipient, - and the sending agent has received at least one message from the recipient, - and the last encrypted message received from the recipient had a trusted signature on it, then the outgoing message SHOULD use the same encryption algorithm as was used on the last signed and encrypted message received from the recipient.
如果：-发送代理不知道收件人的加密功能，-并且发送代理已从收件人收到至少一封邮件，-并且从收件人收到的最后一封加密邮件上有可信签名，然后，传出消息应使用与上次从收件人接收的签名和加密消息相同的加密算法。
If: - the sending agent has no knowledge of the encryption capabilities of the recipient, - and the sending agent is willing to risk that the recipient may not be able to decrypt the message, then the sending agent SHOULD use tripleDES.
如果：-发送代理不知道收件人的加密功能，-并且发送代理愿意冒收件人可能无法解密邮件的风险，则发送代理应使用tripleDES。
If: - the sending agent has no knowledge of the encryption capabilities of the recipient, - and the sending agent is not willing to risk that the recipient may not be able to decrypt the message, then the sending agent MUST use RC2/40.
如果：-发送代理不知道收件人的加密功能，-并且发送代理不愿意冒收件人可能无法解密邮件的风险，则发送代理必须使用RC2/40。
Like all algorithms that use 40 bit keys, RC2/40 is considered by many to be weak encryption. A sending agent that is controlled by a human SHOULD allow a human sender to determine the risks of sending data using RC2/40 or a similarly weak encryption algorithm before sending the data, and possibly allow the human to use a stronger encryption method such as tripleDES.
像所有使用40位密钥的算法一样，许多人认为RC2/40是弱加密。由人工控制的发送代理应允许人工发送者在发送数据之前确定使用RC2/40或类似弱加密算法发送数据的风险，并可能允许人工使用更强的加密方法，如tripleDES。
If a sending agent is composing an encrypted message to a group of recipients where the encryption capabilities of some of the recipients do not overlap, the sending agent is forced to send more than one message. It should be noted that if the sending agent chooses to send a message encrypted with a strong algorithm, and then send the same message encrypted with a weak algorithm, someone watching the communications channel can decipher the contents of the strongly-encrypted message simply by decrypting the weakly-encrypted message.
如果发送代理正在向一组收件人发送加密邮件，其中某些收件人的加密功能不重叠，则发送代理将被迫发送多条邮件。应注意，如果发送代理选择发送使用强算法加密的消息，然后发送使用弱算法加密的相同消息，则监视通信信道的人可以通过解密弱加密消息来解密强加密消息的内容。
This section describes the S/MIME message formats and how they are created. S/MIME messages are a combination of MIME bodies and PKCS objects. Several MIME types as well as several PKCS objects are used. The data to be secured is always a canonical MIME entity. The MIME entity and other data, such as certificates and algorithm identifiers, are given to PKCS processing facilities which produces a PKCS object. The PKCS object is then finally wrapped in MIME.
本节介绍S/MIME消息格式及其创建方式。S/MIME消息是MIME主体和PKCS对象的组合。使用了几种MIME类型以及几种PKCS对象。要保护的数据始终是规范的MIME实体。MIME实体和其他数据（如证书和算法标识符）被提供给生成PKCS对象的PKCS处理设施。PKCS对象最后被包装成MIME。
S/MIME provides one format for enveloped-only data, several formats for signed-only data, and several formats for signed and enveloped data. Several formats are required to accommodate several environments, in particular for signed messages. The criteria for choosing among these formats are also described.
S/MIME为仅封装数据提供了一种格式，为仅签名数据提供了几种格式，为签名和封装数据提供了几种格式。需要多种格式来适应多种环境，特别是对于签名消息。还描述了在这些格式中选择的标准。
The reader of this section is expected to understand MIME as described in [MIME-SPEC] and [MIME-SECURE].
本节的读者应理解[MIME-SPEC]和[MIME-SECURE]中所述的MIME。
S/MIME is used to secure MIME entities. A MIME entity may be a sub-part, sub-parts of a message, or the whole message with all its sub-parts. A MIME entity that is the whole message includes only the MIME headers and MIME body, and does not include the RFC-822 headers. Note that S/MIME can also be used to secure MIME entities used in applications other than Internet mail.
S/MIME用于保护MIME实体。MIME实体可以是消息的子部分或子部分，也可以是整个消息及其所有子部分。作为整个消息的MIME实体只包括MIME头和MIME体，不包括RFC-822头。请注意，S/MIME还可用于保护除Internet邮件以外的应用程序中使用的MIME实体。
The MIME entity that is secured and described in this section can be thought of as the "inside" MIME entity. That is, it is the "innermost" object in what is possibly a larger MIME message. Processing "outside" MIME entities into PKCS #7 objects is described in Section 3.2, 3.4 and elsewhere.
本节中描述的受保护MIME实体可以被视为“内部”MIME实体。也就是说，它可能是更大的MIME消息中的“最内层”对象。将“外部”MIME实体处理为PKCS#7对象在第3.2节、第3.4节和其他地方进行了描述。
The procedure for preparing a MIME entity is given in [MIME-SPEC]. The same procedure is used here with some additional restrictions when signing. Description of the procedures from [MIME-SPEC] are repeated here, but the reader should refer to that document for the exact procedure. This section also describes additional requirements.
[MIME-SPEC]中给出了准备MIME实体的过程。这里使用相同的过程，但在签名时有一些附加限制。此处重复[MIME-SPEC]中的过程描述，但读者应参考该文档了解确切的过程。本节还描述了其他要求。
A single procedure is used for creating MIME entities that are to be signed, enveloped, or both signed and enveloped. Some additional steps are recommended to defend against known corruptions that can occur during mail transport that are of particular importance for clear-signing using the multipart/signed format. It is recommended that these additional steps be performed on enveloped messages, or signed and enveloped messages in order that the message can be forwarded to any environment without modification.
单个过程用于创建要签名、封装或同时签名和封装的MIME实体。建议采取一些额外的步骤来防止邮件传输过程中可能发生的已知损坏，这些损坏对于使用多部分/签名格式的清除签名特别重要。建议对封装的消息或签名和封装的消息执行这些附加步骤，以便在不进行修改的情况下将消息转发到任何环境。
These steps are descriptive rather than prescriptive. The implementor is free to use any procedure as long as the result is the same.
这些步骤是描述性的，而不是规定性的。只要结果相同，实现者就可以自由使用任何过程。
Step 1. The MIME entity is prepared according to the local conventions
第一步。MIME实体是根据本地约定准备的
Step 2. The leaf parts of the MIME entity are converted to canonical form
第二步。MIME实体的叶部分将转换为规范形式
Step 3. Appropriate transfer encoding is applied to the leaves of the MIME entity
第三步。对MIME实体的叶子应用适当的传输编码
When an S/MIME message is received, the security services on the message are removed, and the result is the MIME entity. That MIME entity is typically passed to a MIME-capable user agent where, it is further decoded and presented to the user or receiving application.
当接收到S/MIME消息时，消息上的安全服务将被删除，结果是MIME实体。该MIME实体通常被传递给支持MIME的用户代理，在该代理中，它被进一步解码并呈现给用户或接收应用程序。
Each MIME entity MUST be converted to a canonical form that is uniquely and unambiguously representable in the environment where the signature is created and the environment where the signature will be verified. MIME entities MUST be canonicalized for enveloping as well as signing.
必须将每个MIME实体转换为规范形式，该规范形式在创建签名的环境和验证签名的环境中唯一且明确地表示。MIME实体必须规范化才能进行封装和签名。
The exact details of canonicalization depend on the actual MIME type and subtype of an entity, and are not described here. Instead, the standard for the particular MIME type should be consulted. For example, canonicalization of type text/plain is different from canonicalization of audio/basic. Other than text types, most types have only one representation regardless of computing platform or environment which can be considered their canonical representation. In general, canonicalization will be performed by the sending agent rather than the S/MIME implementation.
规范化的确切细节取决于实体的实际MIME类型和子类型，此处不作描述。相反，应该参考特定MIME类型的标准。例如，text/plain类型的规范化不同于audio/basic类型的规范化。除了文本类型之外，大多数类型只有一种表示形式，而不管计算平台或环境如何，这可以被视为它们的规范表示形式。通常，规范化将由发送代理执行，而不是由S/MIME实现执行。
The most common and important canonicalization is for text, which is often represented differently in different environments. MIME entities of major type "text" must have both their line endings and character set canonicalized. The line ending must be the pair of characters <CR><LF>, and the charset should be a registered charset [CHARSETS]. The details of the canonicalization are specified in [MIME-SPEC]. The chosen charset SHOULD be named in the charset parameter so that the receiving agent can unambiguously determine the charset used.
最常见和最重要的规范化是针对文本的规范化，在不同的环境中，文本通常有不同的表示。主要类型为“text”的MIME实体的行尾和字符集都必须规范化。行尾必须是一对字符<CR><LF>，并且字符集应该是注册的字符集[charset]。规范化的详细信息在[MIME-SPEC]中指定。所选的字符集应该在charset参数中命名，以便接收代理可以明确地确定使用的字符集。
Note that some charsets such as ISO-2022 have multiple representations for the same characters. When preparing such text for signing, the canonical representation specified for the charset MUST be used.
请注意，某些字符集（如ISO-2022）具有相同字符的多个表示形式。准备此类文本进行签名时，必须使用为字符集指定的规范表示。
When generating any of the secured MIME entities below, except the signing using the multipart/signed format, no transfer encoding at all is required. S/MIME implementations MUST be able to deal with binary MIME objects. If no Content-Transfer-Encoding header is present, the transfer encoding should be considered 7BIT.
生成以下任何受保护的MIME实体时，除了使用多部分/签名格式的签名外，根本不需要传输编码。S/MIME实现必须能够处理二进制MIME对象。如果不存在内容传输编码头，则应将传输编码视为它。
S/MIME implementations SHOULD however use transfer encoding described in section 3.1.3 for all MIME entities they secure. The reason for securing only 7-bit MIME entities, even for enveloped data that are not exposed to the transport, is that it allows the MIME entity to be handled in any environment without changing it. For example, a trusted gateway might remove the envelope, but not the signature, of a message, and then forward the signed message on to the end
但是，S/MIME实现应使用第3.1.3节中所述的传输编码来保护所有MIME实体。仅保护7位MIME实体的原因是，它允许在任何环境中处理MIME实体，而无需对其进行更改，即使对于未暴露于传输的封装数据也是如此。例如，可信网关可能会删除消息的信封，但不会删除签名，然后将签名的消息转发到最后
recipient so that they can verify the signatures directly. If the transport internal to the site is not 8-bit clean, such as on a wide-area network with a single mail gateway, verifying the signature will not be possible unless the original MIME entity was only 7-bit data.
收件人，以便他们可以直接验证签名。如果站点内部的传输不是8位干净的，例如在具有单个邮件网关的广域网上，则无法验证签名，除非原始MIME实体仅为7位数据。
If a multipart/signed entity is EVER to be transmitted over the standard Internet SMTP infrastructure or other transport that is constrained to 7-bit text, it MUST have transfer encoding applied so that it is represented as 7-bit text. MIME entities that are 7-bit data already need no transfer encoding. Entities such as 8-bit text and binary data can be encoded with quoted-printable or base-64 transfer encoding.
如果要通过标准Internet SMTP基础设施或其他限制为7位文本的传输传输多部分/签名实体，则必须应用传输编码，以便将其表示为7位文本。7位数据的MIME实体已经不需要传输编码。实体（如8位文本和二进制数据）可以使用带引号的可打印或base-64传输编码进行编码。
The primary reason for the 7-bit requirement is that the Internet mail transport infrastructure cannot guarantee transport of 8-bit or binary data. Even though many segments of the transport infrastructure now handle 8-bit and even binary data, it is sometimes not possible to know whether the transport path is 8-bit clear. If a mail message with 8-bit data were to encounter a message transfer agent that can not transmit 8-bit or binary data, the agent has three options, none of which are acceptable for a clear-signed message: - The agent could change the transfer encoding; this would invalidate the signature. - The agent could transmit the data anyway, which would most likely result in the 8th bit being corrupted; this too would invalidate the signature. - The agent could return the message to the sender.
7位要求的主要原因是Internet邮件传输基础设施无法保证8位或二进制数据的传输。尽管传输基础设施的许多部分现在处理8位甚至二进制数据，但有时不可能知道传输路径是否为8位。如果具有8位数据的邮件遇到无法传输8位或二进制数据的邮件传输代理，则该代理有三个选项，其中任何选项都不适用于无签名邮件：-该代理可以更改传输编码；这将使签名无效代理无论如何都可以传输数据，这很可能导致第8位被破坏；这也会使签名无效代理可以将邮件返回给发件人。
[MIME-SECURE] prohibits an agent from changing the transfer encoding of the first part of a multipart/signed message. If a compliant agent that can not transmit 8-bit or binary data encounters a multipart/signed message with 8-bit or binary data in the first part, it would have to return the message to the sender as undeliverable.
[MIME-SECURE]禁止代理更改多部分/签名消息第一部分的传输编码。如果无法传输8位或二进制数据的兼容代理在第一部分遇到包含8位或二进制数据的多部分/签名消息，则必须将消息作为无法送达返回给发送方。
This example shows a multipart/mixed message with full transfer encoding. This message contains a text part and an attachment. The sample message text includes characters that are not US-ASCII and thus must be transfer encoded. Though not shown here, the end of each line is <CR><LF>. The line ending of the MIME headers, the text, and transfer encoded parts, all must be <CR><LF>.
此示例显示了具有完全传输编码的多部分/混合消息。此邮件包含文本部分和附件。示例消息文本包含非US-ASCII字符，因此必须进行传输编码。虽然此处未显示，但每行的末尾都是<CR><LF>。MIME头、文本和传输编码部分的行尾都必须是<CR><LF>。
Note that this example is not of an S/MIME message.
请注意，此示例不是S/MIME消息的示例。
Content-Type: multipart/mixed; boundary=bar
Content-Type: multipart/mixed; boundary=bar
--bar
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable
--bar
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable
=A1Hola Michael!
嗨，迈克尔！
How do you like the new S/MIME specification?
您觉得新的S/MIME规范怎么样？
I agree. It's generally a good idea to encode lines that begin with From=20because some mail transport agents will insert a greater-than (>) sign, thus invalidating the signature.
我同意。通常最好对以From=20开头的行进行编码，因为某些邮件传输代理会插入大于（>）的符号，从而使签名无效。
Also, in some cases it might be desirable to encode any =20 trailing whitespace that occurs on lines in order to ensure =20 that the message signature is not invalidated when passing =20 a gateway that modifies such whitespace (like BITNET). =20
此外，在某些情况下，可能需要对行上出现的任何=20尾随空格进行编码，以确保在传递=20修改此类空格的网关（如BITNET）时，消息签名不会失效=20
--bar
Content-Type: image/jpeg
Content-Transfer-Encoding: base64
--bar
Content-Type: image/jpeg
Content-Transfer-Encoding: base64
iQCVAwUBMJrRF2N9oWBghPDJAQE9UQQAtl7LuRVndBjrk4EqYBIb3h5QXIX/LC//
jJV5bNvkZIGPIcEmI5iFd9boEgvpirHtIREEqLQRkYNoBActFBZmh9GC3C041WGq
uMbrbxc+nIs1TIKlA08rVi9ig/2Yh7LFrK5Ein57U/W72vgSxLhe/zhdfolT9Brn
HOxEa44b+EI=
iQCVAwUBMJrRF2N9oWBghPDJAQE9UQQAtl7LuRVndBjrk4EqYBIb3h5QXIX/LC//
jJV5bNvkZIGPIcEmI5iFd9boEgvpirHtIREEqLQRkYNoBActFBZmh9GC3C041WGq
uMbrbxc+nIs1TIKlA08rVi9ig/2Yh7LFrK5Ein57U/W72vgSxLhe/zhdfolT9Brn
HOxEa44b+EI=
--bar--
--酒吧--
The application/pkcs7-mime type is used to carry PKCS #7 objects of several types including envelopedData and signedData. The details of constructing these entities is described in subsequent sections. This section describes the general characteristics of the application/pkcs7-mime type.
application/pkcs7 mime类型用于承载PKCS#7多种类型的对象，包括envelopedData和signedData。构建这些实体的详细信息将在后续章节中介绍。本节介绍application/pkcs7 mime类型的一般特征。
This MIME type always carries a single PKCS #7 object. The PKCS #7 object must always be BER encoding of the ASN.1 syntax describing the object. The contentInfo field of the carried PKCS #7 object always contains a MIME entity that is prepared as described in section 3.1. The contentInfo field must never be empty.
此MIME类型始终携带一个PKCS#7对象。PKCS#7对象必须始终是描述该对象的ASN.1语法的BER编码。所携带PKCS#7对象的contentInfo字段始终包含按照第3.1节所述准备的MIME实体。contentInfo字段不能为空。
Since PKCS #7 objects are binary data, in most cases base-64 transfer encoding is appropriate, in particular when used with SMTP transport. The transfer encoding used depends on the transport through which the object is to be sent, and is not a characteristic of the MIME type.
由于PKCS#7对象是二进制数据，因此在大多数情况下，base-64传输编码是合适的，尤其是在与SMTP传输一起使用时。所使用的传输编码取决于要发送对象的传输，而不是MIME类型的特征。
Note that this discussion refers to the transfer encoding of the PKCS #7 object or "outside" MIME entity. It is completely distinct from, and unrelated to, the transfer encoding of the MIME entity secured by the PKCS #7 object, the "inside" object, which is described in section 3.1.
请注意，此讨论涉及PKCS#7对象或“外部”MIME实体的传输编码。它与PKCS#7对象（第3.1节中描述的“内部”对象）保护的MIME实体的传输编码完全不同，也不相关。
Because there are several types of application/pkcs7-mime objects, a sending agent SHOULD do as much as possible to help a receiving agent know about the contents of the object without forcing the receiving agent to decode the ASN.1 for the object. The MIME headers of all application/pkcs7-mime objects SHOULD include the optional "smime-type" parameter, as described in the following sections.
由于存在多种类型的application/pkcs7 mime对象，因此发送代理应尽可能帮助接收代理了解对象的内容，而无需强制接收代理解码对象的ASN.1。所有application/pkcs7 MIME对象的MIME头都应包含可选的“smime type”参数，如以下各节所述。
For the application/pkcs7-mime, sending agents SHOULD emit the optional "name" parameter to the Content-Type field for compatibility with older systems. Sending agents SHOULD also emit the optional Content-Disposition field [CONTDISP] with the "filename" parameter. If a sending agent emits the above parameters, the value of the parameters SHOULD be a file name with the appropriate extension:
对于application/pkcs7 mime，发送代理应该向Content-Type字段发出可选的“name”参数，以便与旧系统兼容。发送代理还应发出带有“filename”参数的可选内容处置字段[CONTDISP]。如果发送代理发出上述参数，则参数值应为具有适当扩展名的文件名：
MIME Type File Extension
MIME类型文件扩展名
application/pkcs7-mime .p7m (signedData, envelopedData)
应用程序/pkcs7 mime.p7m（签名数据、信封数据）
application/pkcs7-mime .p7c (degenerate signedData "certs-only" message)
application/pkcs7 mime.p7c（退化签名数据“仅证书”消息）
application/pkcs7-signature .p7s
应用程序/pkcs7签名.p7s
application/pkcs10 .p10
application/pkcs10.p10
In addition, the file name SHOULD be limited to eight characters followed by a three letter extension. The eight character filename base can be any distinct name; the use of the filename base "smime" SHOULD be used to indicate that the MIME entity is associated with S/MIME.
此外，文件名应限制为八个字符，后跟三个字母的扩展名。八个字符的文件名基可以是任何不同的名称；应使用文件名基“smime”来指示MIME实体与S/MIME关联。
Including a file name serves two purposes. It facilitates easier use of S/MIME objects as files on disk. It also can convey type information across gateways. When a MIME entity of type application/pkcs7-mime (for example) arrives at a gateway that has no special knowledge of S/MIME, it will default the entity's MIME type to application/octet-stream and treat it as a generic attachment, thus losing the type information. However, the suggested filename for
包含文件名有两个目的。它便于将S/MIME对象作为磁盘上的文件使用。它还可以跨网关传递类型信息。例如，当类型为application/pkcs7 MIME的MIME实体到达对S/MIME没有特殊知识的网关时，它会将该实体的MIME类型默认为application/octet stream，并将其视为通用附件，从而丢失类型信息。但是，建议的
an attachment is often carried across a gateway. This often allows the receiving systems to determine the appropriate application to hand the attachment off to, in this case a stand-alone S/MIME processing application. Note that this mechanism is provided as a convenience for implementations in certain environments. A proper S/MIME implementation MUST use the MIME types and MUST NOT rely on the file extensions.
附件通常通过网关携带。这通常允许接收系统确定将附件转交给独立S/MIME处理应用程序的适当应用程序。请注意，提供此机制是为了方便在某些环境中实现。正确的S/MIME实现必须使用MIME类型，并且不能依赖于文件扩展名。
This section describes the format for enveloping a MIME entity without signing it.
本节描述了封装MIME实体而不进行签名的格式。
Step 1. The MIME entity to be enveloped is prepared according to section 3.1.
第一步。要封装的MIME实体根据第3.1节准备。
Step 2. The MIME entity and other required data is processed into a PKCS #7 object of type envelopedData.
第二步。MIME实体和其他必需的数据被处理成envelopedData类型的PKCS#7对象。
Step 3. The PKCS #7 object is inserted into an application/pkcs7- mime MIME entity.
第三步。pkcs7对象被插入到application/pkcs7-mime mime实体中。
The smime-type parameter for enveloped-only messages is "enveloped-data". The file extension for this type of message is ".p7m".
仅信封消息的smime类型参数为“信封数据”。此类消息的文件扩展名为“.p7m”。
A sample message would be:
示例消息如下：
Content-Type: application/pkcs7-mime; smime-type=enveloped-data;
name=smime.p7m
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7m
Content-Type: application/pkcs7-mime; smime-type=enveloped-data;
name=smime.p7m
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7m
rfvbnj756tbBghyHhHUujhJhjH77n8HHGT9HG4VQpfyF467GhIGfHfYT6 7n8HHGghyHhHUujhJh4VQpfyF467GhIGfHfYGTrfvbnjT6jH7756tbB9H f8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfHfYT6ghyHhHUujpfyF4 0GhIGfHfQbnj756YT64V
RFVBNJ756BBGHYHHHHHUJHJH77N8HGT9HG4VQPFYF467N8HGHGHHHHHHHHHHHHHJH4VQPFF467GHIGFHFYGTRFFBNJT6JH7756TBB9H F8HGHGTRFVHJHHJH776BB9HG4VQBNJ7567GHIGFYT6GHYHHHHHHHHJFFFF4 0GhIGfHfQbnj756YT64V
There are two formats for signed messages defined for S/MIME: application/pkcs7-mime and SignedData, and multipart/signed. In general, the multipart/signed form is preferred for sending, and receiving agents SHOULD be able to handle both.
为S/MIME定义的签名消息有两种格式：application/pkcs7 MIME和SignedData，以及multipart/signed。一般来说，发送时首选多部分/签名表单，而接收代理应该能够处理这两种表单。
There are no hard-and-fast rules when a particular signed-only format should be chosen because it depends on the capabilities of all the
在选择特定的仅签名格式时没有硬性规定，因为它取决于所有用户的能力
receivers and the relative importance of receivers with S/MIME facilities being able to verify the signature versus the importance of receivers without S/MIME software being able to view the message.
接收者和具有能够验证签名的S/MIME设施的接收者的相对重要性，以及没有能够查看消息的S/MIME软件的接收者的相对重要性。
Messages signed using the multipart/signed format can always be viewed by the receiver whether they have S/MIME software or not. They can also be viewed whether they are using a MIME-native user agent or they have messages translated by a gateway. In this context, "be viewed" means the ability to process the message essentially as if it were not a signed message, including any other MIME structure the message might have.
无论接收方是否使用S/MIME软件，都可以查看使用多部分/签名格式签名的消息。也可以查看它们是使用MIME本机用户代理，还是通过网关翻译消息。在这种情况下，“被查看”意味着处理消息的能力，本质上就好像它不是一个签名消息一样，包括消息可能具有的任何其他MIME结构。
Messages signed using the signedData format cannot be viewed by a recipient unless they have S/MIME facilities. However, if they have S/MIME facilities, these messages can always be verified if they were not changed in transit.
收件人无法查看使用signedData格式签名的邮件，除非这些邮件具有S/MIME功能。但是，如果它们具有S/MIME功能，则如果在传输过程中没有更改，则始终可以验证这些消息。
This signing format uses the application/pkcs7-mime MIME type. The steps to create this format are:
此签名格式使用application/pkcs7 mime mime类型。创建此格式的步骤包括：
Step 1. The MIME entity is prepared according to section 3.1
第一步。MIME实体是根据第3.1节准备的
Step 2. The MIME entity and other required data is processed into a PKCS #7 object of type signedData
第二步。MIME实体和其他必需的数据被处理成signedData类型的PKCS#7对象
Step 3. The PKCS #7 object is inserted into an application/pkcs7-mime MIME entity
第三步。PKCS#7对象被插入到应用程序/pkcs7 mime实体中
The smime-type parameter for messages using application/pkcs7-mime and SignedData is "signed-data". The file extension for this type of message is ".p7m".
使用application/pkcs7 mime和SignedData的消息的smime类型参数为“signed data”。此类消息的文件扩展名为“.p7m”。
A sample message would be:
示例消息如下：
Content-Type: application/pkcs7-mime; smime-type=signed-data;
name=smime.p7m
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7m
Content-Type: application/pkcs7-mime; smime-type=signed-data;
name=smime.p7m
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7m
567GhIGfHfYT6ghyHhHUujpfyF4f8HHGTrfvhJhjH776tbB9HG4VQbnj7 77n8HHGT9HG4VQpfyF467GhIGfHfYT6rfvbnj756tbBghyHhHUujhJhjH HUujhJh4VQpfyF467GhIGfHfYGTrfvbnjT6jH7756tbB9H7n8HHGghyHh 6YT64V0GhIGfHfQbnj75
567GHIGHFYT6GHYHHHHHUJPFYFF4F8HGFFYT6GHYHHHHHJHFFFFFFJH776BB9Hg4VQBNJ7 77N8HgT9Hg4VQPFFYF467GHIGHFYT6RFVBNJ756BBGHHHHHHHHHHHHHJHFFFFFFJJH6JH7756TBB9H7N8HGHGHGHGHGHGHGHGHGHGHFYH6YH6YH64V0GHIGHFQBNJ75
This format is a clear-signing format. Recipients without any S/MIME or PKCS processing facilities are able to view the message. It makes use of the multipart/signed MIME type described in [MIME-SECURE]. The multipart/signed MIME type has two parts. The first part contains the MIME entity that is to be signed; the second part contains the signature, which is a PKCS #7 detached signature.
此格式是一种清晰的签名格式。没有任何S/MIME或PKCS处理设施的收件人可以查看邮件。它使用[MIME-SECURE]中描述的多部分/签名MIME类型。多部分/签名MIME类型有两部分。第一部分包含要签名的MIME实体；第二部分包含签名，它是PKCS#7分离签名。
This MIME type always contains a single PKCS #7 object of type signedData. The contentInfo field of the PKCS #7 object must be empty. The signerInfos field contains the signatures for the MIME entity. The details of the registered type are given in Appendix D.
此MIME类型始终包含一个signedData类型的PKCS#7对象。PKCS#7对象的contentInfo字段必须为空。signerInfos字段包含MIME实体的签名。注册类型的详细信息见附录D。
The file extension for signed-only messages using application/pkcs7- signature is ".p7s".
使用application/pkcs7-signature的仅签名消息的文件扩展名为“.p7s”。
Step 1. The MIME entity to be signed is prepared according to section 3.1, taking special care for clear-signing.
第一步。要签名的MIME实体是根据第3.1节准备的，特别注意清晰签名。
Step 2. The MIME entity is presented to PKCS #7 processing in order to obtain an object of type signedData with an empty contentInfo field.
第二步。MIME实体将呈现给PKCS#7处理，以获取一个带有空contentInfo字段的signedData类型的对象。
Step 3. The MIME entity is inserted into the first part of a multipart/signed message with no processing other than that described in section 3.1.
第三步。MIME实体插入到多部分/签名消息的第一部分，除第3.1节所述的处理外，不进行任何处理。
Step 4. Transfer encoding is applied to the detached signature and it is inserted into a MIME entity of type application/pkcs7-signature
第四步。传输编码应用于分离的签名，并插入到类型为application/pkcs7 signature的MIME实体中
Step 5. The MIME entity of the application/pkcs7-signature is inserted into the second part of the multipart/signed entity
第五步。应用程序/pkcs7签名的MIME实体插入到多部分/签名实体的第二部分
The multipart/signed Content type has two required parameters: the protocol parameter and the micalg parameter.
多部分/签名内容类型有两个必需的参数：协议参数和micalg参数。
The protocol parameter MUST be "application/pkcs7-signature". Note that quotation marks are required around the protocol parameter because MIME requires that the "/" character in the parameter value MUST be quoted.
协议参数必须是“应用程序/pkcs7签名”。请注意，协议参数周围需要引号，因为MIME要求必须引用参数值中的“/”字符。
The micalg parameter allows for one-pass processing when the signature is being verified. The value of the micalg parameter is dependent on the message digest algorithm used in the calculation of the Message Integrity Check. The value of the micalg parameter SHOULD be one of the following:
验证签名时，micalg参数允许一次通过处理。micalg参数的值取决于计算消息完整性检查时使用的消息摘要算法。micalg参数的值应为以下值之一：
Algorithm used Value
-------------- ---------
MD5 md5
SHA-1 sha1
any other unknown
Algorithm used Value
-------------- ---------
MD5 md5
SHA-1 sha1
any other unknown
(Historical note: some early implementations of S/MIME emitted and expected "rsa-md5" and "rsa-sha1" for the micalg parameter.) Receiving agents SHOULD be able to recover gracefully from a micalg parameter value that they do not recognize.
（历史记录：S/MIME的一些早期实现已发出，预期micalg参数为“rsa-md5”和“rsa-sha1”）。接收代理应该能够从它们无法识别的micalg参数值中正常恢复。
Content-Type: multipart/signed;
protocol="application/pkcs7-signature";
micalg=sha1; boundary=boundary42
Content-Type: multipart/signed;
protocol="application/pkcs7-signature";
micalg=sha1; boundary=boundary42
--boundary42
Content-Type: text/plain
--boundary42
Content-Type: text/plain
This is a clear-signed message.
这是一条清晰的签名信息。
--boundary42
Content-Type: application/pkcs7-signature; name=smime.p7s
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7s
--boundary42
Content-Type: application/pkcs7-signature; name=smime.p7s
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7s
ghyHhHUujhJhjH77n8HHGTrfvbnj756tbB9HG4VQpfyF467GhIGfHfYT6 4VQpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756tbB9HGTrfvbnj n8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfHfYT6ghyHhHUujpfyF4 7GhIGfHfYT64VQbnj756
Ghyhhhhhhhhhhhhhhhhhhjhjh77n8hghtrfvbnj756tb9hg4vqpfyf467ghighfyt6 4vqpfyf467ghighfyt6jhhhhhhhhhhhhhhhhhhhhhjhjh756tb9hgtrffbnj n8hghtrfvhhhhhhhhhhhhhj776bb9hg4vqbnj7567ghigfyfyfyfyfyf4 7ghigff
--boundary42--
--边界42--
To achieve signing and enveloping, any of the signed-only and encrypted-only formats may be nested. This is allowed because the above formats are all MIME entities, and because they all secure MIME entities.
为了实现签名和封装，可以嵌套任何仅签名和仅加密的格式。这是允许的，因为上述格式都是MIME实体，并且都是安全的MIME实体。
An S/MIME implementation MUST be able to receive and process arbitrarily nested S/MIME within reasonable resource limits of the recipient computer.
S/MIME实现必须能够在接收方计算机的合理资源限制内接收和处理任意嵌套的S/MIME。
It is possible to either sign a message first, or to envelope the message first. It is up to the implementor and the user to choose. When signing first, the signatories are then securely obscured by the enveloping. When enveloping first the signatories are exposed, but it is possible to verify signatures without removing the enveloping. This may be useful in an environment were automatic signature verification is desired, as no private key material is required to verify a signature.
可以先对消息进行签名，也可以先对消息进行封装。这取决于实现者和用户的选择。首先签字时，签字人会被信封牢牢遮挡。当第一次封装时，签名人会暴露出来，但可以在不移除封装的情况下验证签名。这在需要自动签名验证的环境中可能很有用，因为验证签名不需要私钥材料。
The certificates only message or MIME entity is used to transport certificates, such as in response to a registration request. This format can also be used to convey CRLs.
仅证书消息或MIME实体用于传输证书，例如响应注册请求。此格式也可用于传送CRL。
Step 1. The certificates are made available to the PKCS #7 generating process which creates a PKCS #7 object of type signedData. The contentInfo and signerInfos fields must be empty.
第一步。证书可用于PKCS#7生成进程，该进程创建signedData类型的PKCS#7对象。contentInfo和signerInfos字段必须为空。
Step 2. The PKCS #7 signedData object is enclosed in an application/pkcs7-mime MIME entity
第二步。PKCS#7 signedData对象包含在application/pkcs7 mime mime实体中
The smime-type parameter for a certs-only message is "certs-only". The file extension for this type of message is ".p7c".
仅证书消息的smime类型参数为“仅证书”。此类消息的文件扩展名为“.p7c”。
A typical application which allows a user to generate cryptographic information has to submit that information to a certification authority, who transforms it into a certificate. PKCS #10 describes a syntax for certification requests. The application/pkcs10 body type MUST be used to transfer a PKCS #10 certification request.
允许用户生成加密信息的典型应用程序必须将该信息提交给证书颁发机构，证书颁发机构将其转换为证书。PKCS#10描述了认证请求的语法。应用程序/pkcs10主体类型必须用于传输PKCS#10认证请求。
The details of certification requests and the process of obtaining a certificate are beyond the scope of this memo. Instead, only the format of data used in application/pkcs10 is defined.
认证申请的详细信息和获取证书的过程超出了本备忘录的范围。相反，只定义了application/pkcs10中使用的数据格式。
PKCS #10 defines the ASN.1 type CertificationRequest for use in submitting a certification request. Therefore, when the MIME content type application/pkcs10 is used, the body MUST be a CertificationRequest, encoded using the Basic Encoding Rules (BER).
PKCS#10定义了ASN.1类型的CertificationRequest，用于提交认证请求。因此，当使用MIME内容类型应用程序/pkcs10时，主体必须是CertificationRequest，使用基本编码规则（BER）进行编码。
Although BER is specified, instead of the more restrictive DER, a typical application will use DER since the CertificationRequest's CertificationRequestInfo has to be DER-encoded in order to be signed. A robust application SHOULD output DER, but allow BER or DER on input.
虽然指定了BER，但典型的应用程序将使用DER，而不是更严格的DER，因为CertificationRequest的CertificationRequestInfo必须进行DER编码才能签名。一个健壮的应用程序应该输出DER，但在输入时允许BER或DER。
Data produced by BER or DER is 8-bit, but many transports are limited to 7-bit data. Therefore, a suitable 7-bit Content-Transfer-Encoding SHOULD be applied. The base64 Content-Transfer-Encoding SHOULD be used with application/pkcs10, although any 7-bit transfer encoding may work.
BER或DER产生的数据为8位，但许多传输仅限于7位数据。因此，应采用合适的7位内容传输编码。base64内容传输编码应与application/pkcs10一起使用，尽管任何7位传输编码都可以工作。
For sending a certificate-signing request, the application/pkcs10 message format MUST be used to convey a PKCS #10 certificate-signing request. Note that for sending certificates and CRLs messages without any signed content, the application/pkcs7-mime message format MUST be used to convey a degenerate PKCS #7 signedData "certs-only" message.
要发送证书签名请求，必须使用application/pkcs10消息格式传递PKCS#10证书签名请求。请注意，要发送没有任何签名内容的证书和CRLs消息，必须使用application/pkcs7 mime消息格式来传递退化的PKCS#7 signedData“certs only”消息。
To send an application/pkcs10 body, the application generates the cryptographic information for the user. The details of the cryptographic information are beyond the scope of this memo.
要发送应用程序/pkcs10正文，应用程序将为用户生成加密信息。加密信息的详细信息超出了本备忘录的范围。
Step 1. The cryptographic information is placed within a PKCS #10 CertificationRequest.
第一步。加密信息放在PKCS#10 CertificationRequest中。
Step 2. The CertificationRequest is encoded according to BER or DER (typically, DER).
第二步。CertificationRequest根据BER或DER（通常为DER）进行编码。
Step 3. As a typical step, the DER-encoded CertificationRequest is also base64 encoded so that it is 7-bit data suitable for transfer in SMTP. This then becomes the body of an application/pkcs10 body part.
第三步。作为一个典型步骤，DER编码的CertificationRequest也是base64编码的，因此它是适合在SMTP中传输的7位数据。这将成为应用程序/pkcs10主体部分的主体。
The result might look like this:
结果可能如下所示：
Content-Type: application/pkcs10; name=smime.p10
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p10
Content-Type: application/pkcs10; name=smime.p10
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p10
rfvbnj756tbBghyHhHUujhJhjH77n8HHGT9HG4VQpfyF467GhIGfHfYT6 7n8HHGghyHhHUujhJh4VQpfyF467GhIGfHfYGTrfvbnjT6jH7756tbB9H f8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfHfYT6ghyHhHUujpfyF4 0GhIGfHfQbnj756YT64V
RFVBNJ756BBGHYHHHHHUJHJH77N8HGT9HG4VQPFYF467N8HGHGHHHHHHHHHHHHHJH4VQPFF467GHIGFHFYGTRFFBNJT6JH7756TBB9H F8HGHGTRFVHJHHJH776BB9HG4VQBNJ7567GHIGFYT6GHYHHHHHHHHJFFFF4 0GhIGfHfQbnj756YT64V
A typical application only needs to send a certification request. It is a certification authority that has to receive and process the
典型的应用程序只需要发送一个认证请求。它是一个认证机构，必须接收和处理
request. The steps for recovering the CertificationRequest from the message are straightforward but are not presented here. The procedures for processing the certification request are beyond the scope of this document.
要求从消息中恢复CertificationRequest的步骤很简单，但此处不介绍。处理认证申请的程序超出了本文件的范围。
Because S/MIME takes into account interoperation in non-MIME environments, several different mechanisms are employed to carry the type information, and it becomes a bit difficult to identify S/MIME messages. The following table lists criteria for determining whether or not a message is an S/MIME message. A message is considered an S/MIME message if it matches any below.
由于S/MIME考虑了非MIME环境中的互操作，因此采用了几种不同的机制来承载类型信息，因此识别S/MIME消息变得有点困难。下表列出了确定消息是否为S/MIME消息的标准。如果消息与下面的任何消息匹配，则将其视为S/MIME消息。
The file suffix in the table below comes from the "name" parameter in the content-type header, or the "filename" parameter on the content-disposition header. These parameters that give the file suffix are not listed below as part of the parameter section.
下表中的文件后缀来自“内容类型”标题中的“名称”参数或“内容处置”标题中的“文件名”参数。下面未将这些提供文件后缀的参数作为参数部分列出。
MIME type: application/pkcs7-mime parameters: any file suffix: any
MIME类型：应用程序/pkcs7 MIME参数：任意文件后缀：任意
MIME type: application/pkcs10 parameters: any file suffix: any
MIME类型：应用程序/pkcs10参数：任意文件后缀：任意
MIME type: multipart/signed
parameters: protocol="application/pkcs7-signature"
file suffix: any
MIME type: multipart/signed
parameters: protocol="application/pkcs7-signature"
file suffix: any
MIME type: application/octet-stream parameters: any file suffix: p7m, p7s, aps, p7c, p10
MIME类型：应用程序/八位字节流参数：任何文件后缀：p7m、p7s、aps、p7c、p10
A receiving agent MUST provide some certificate retrieval mechanism in order to gain access to certificates for recipients of digital envelopes. This memo does not cover how S/MIME agents handle certificates, only what they do after a certificate has been validated or rejected. S/MIME certification issues are covered in a different document.
接收代理必须提供某种证书检索机制，以便为数字信封的收件人访问证书。本备忘录不涉及S/MIME代理如何处理证书，只涉及在证书被验证或拒绝后他们会做什么。S/MIME认证问题包含在另一个文档中。
At a minimum, for initial S/MIME deployment, a user agent could automatically generate a message to an intended recipient requesting that recipient's certificate in a signed return message. Receiving and sending agents SHOULD also provide a mechanism to allow a user to
对于初始S/MIME部署，用户代理至少可以自动生成一条消息，发送给指定的收件人，在签名的返回消息中请求该收件人的证书。接收和发送代理还应提供一种机制，允许用户
"store and protect" certificates for correspondents in such a way so as to guarantee their later retrieval.
通讯员的“存储和保护”证书，以保证其以后的检索。
An S/MIME agent or some related administrative utility or function MUST be capable of generating RSA key pairs on behalf of the user. Each key pair MUST be generated from a good source of non-deterministic random input and protected in a secure fashion.
S/MIME代理或某些相关的管理实用程序或函数必须能够代表用户生成RSA密钥对。每个密钥对必须从非确定性随机输入的良好来源生成，并以安全的方式进行保护。
A user agent SHOULD generate RSA key pairs at a minimum key size of 768 bits and a maximum key size of 1024 bits. A user agent MUST NOT generate RSA key pairs less than 512 bits long. Some agents created in the United States have chosen to create 512 bit keys in order to get more advantageous export licenses. However, 512 bit keys are considered by many to be cryptographically insecure.
用户代理应生成最小密钥大小为768位、最大密钥大小为1024位的RSA密钥对。用户代理不能生成长度小于512位的RSA密钥对。在美国创建的一些代理选择创建512位密钥，以获得更有利的出口许可证。然而，许多人认为512位密钥在加密方面是不安全的。
Implementors should be aware that multiple (active) key pairs may be associated with a single individual. For example, one key pair may be used to support confidentiality, while a different key pair may be used for authentication.
实现者应该知道，多个（活动）密钥对可能与单个个体相关联。例如，一个密钥对可用于支持机密性，而不同的密钥对可用于认证。
This entire memo discusses security. Security issues not covered in other parts of the memo include:
这整份备忘录都讨论了安全问题。备忘录其他部分未涉及的安全问题包括：
40-bit encryption is considered weak by most cryptographers. Using weak cryptography in S/MIME offers little actual security over sending plaintext. However, other features of S/MIME, such as the specification of tripleDES and the ability to announce stronger cryptographic capabilities to parties with whom you communicate, allow senders to create messages that use strong encryption. Using weak cryptography is never recommended unless the only alternative is no cryptography. When feasible, sending and receiving agents should inform senders and recipients the relative cryptographic strength of messages.
大多数密码学家认为40位加密很弱。在S/MIME中使用弱加密技术在发送明文时几乎没有实际的安全性。但是，S/MIME的其他功能，如三元组的规范和向与您通信的各方宣布更强加密功能的能力，允许发件人创建使用强加密的消息。除非唯一的选择是不加密，否则永远不建议使用弱加密。在可行的情况下，发送和接收代理应通知发送方和接收方消息的相对加密强度。
It is impossible for most software or people to estimate the value of a message. Further, it is impossible for most software or people to estimate the actual cost of decrypting a message that is encrypted with a key of a particular size. Further, it is quite difficult to determine the cost of a failed decryption if a recipient cannot decode a message. Thus, choosing between different key sizes (or choosing whether to just use plaintext) is also impossible. However, decisions based on these criteria are made all the time, and therefore this memo gives a framework for using those estimates in choosing algorithms.
对于大多数软件或人员来说，估计消息的价值是不可能的。此外，对于大多数软件或人员来说，不可能估计解密使用特定大小的密钥加密的消息的实际成本。此外，如果收件人无法解码消息，则很难确定解密失败的成本。因此，在不同的密钥大小之间进行选择（或者选择是否只使用明文）也是不可能的。然而，基于这些标准的决策一直在做出，因此本备忘录给出了在选择算法时使用这些估计值的框架。
If a sending agent is sending the same message using different strengths of cryptography, an attacker watching the communications channel can determine the contents of the strongly-encrypted message by decrypting the weakly-encrypted version. In other words, a sender should not send a copy of a message using weaker cryptography than they would use for the original of the message.
如果发送代理使用不同的加密强度发送相同的消息，则监视通信通道的攻击者可以通过解密弱加密版本来确定强加密消息的内容。换句话说，发件人不应使用比原始邮件更弱的加密技术发送邮件副本。
A. Object Identifiers and Syntax
A.对象标识符和语法
The syntax for SMIMECapability is:
SMIMECapability的语法为：
SMIMECapability ::= SEQUENCE {
capabilityID OBJECT IDENTIFIER,
parameters OPTIONAL ANY DEFINED BY capabilityID }
SMIMECapability ::= SEQUENCE {
capabilityID OBJECT IDENTIFIER,
parameters OPTIONAL ANY DEFINED BY capabilityID }
SMIMECapabilities ::= SEQUENCE OF SMIMECapability
SMIMECapabilities ::= SEQUENCE OF SMIMECapability
RC2-CBC OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) encryptionAlgorithm(3) 2}
RC2-CBC OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) encryptionAlgorithm(3) 2}
For the effective-key-bits (key size) greater than 32 and less than 256, the RC2-CBC algorithm parameters are encoded as:
对于大于32且小于256的有效密钥位（密钥大小），RC2-CBC算法参数编码为：
RC2-CBC parameter ::= SEQUENCE {
rc2ParameterVersion INTEGER,
iv OCTET STRING (8)}
RC2-CBC parameter ::= SEQUENCE {
rc2ParameterVersion INTEGER,
iv OCTET STRING (8)}
For the effective-key-bits of 40, 64, and 128, the rc2ParameterVersion values are 160, 120, 58 respectively.
对于有效密钥位40、64和128，RC2参数版本值分别为160、120和58。
DES-EDE3-CBC OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) encryptionAlgorithm(3) 7}
DES-EDE3-CBC OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) encryptionAlgorithm(3) 7}
For DES-CBC and DES-EDE3-CBC, the parameter should be encoded as:
对于DES-CBC和DES-EDE3-CBC，参数应编码为：
CBCParameter :: IV
CBC参数：：IV
where IV ::= OCTET STRING -- 8 octets.
where IV ::= OCTET STRING -- 8 octets.
md5 OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) digestAlgorithm(2) 5}
md5 OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) digestAlgorithm(2) 5}
sha-1 OBJECT IDENTIFIER ::=
{iso(1) identified-organization(3) oiw(14) secsig(3) algorithm(2) 26}
sha-1 OBJECT IDENTIFIER ::=
{iso(1) identified-organization(3) oiw(14) secsig(3) algorithm(2) 26}
rsaEncryption OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 1}
rsaEncryption OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 1}
rsa OBJECT IDENTIFIER ::=
{joint-iso-ccitt(2) ds(5) algorithm(8) encryptionAlgorithm(1) 1}
rsa OBJECT IDENTIFIER ::=
{joint-iso-ccitt(2) ds(5) algorithm(8) encryptionAlgorithm(1) 1}
md2WithRSAEncryption OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 2}
md2WithRSAEncryption OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 2}
md5WithRSAEncryption OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 4}
md5WithRSAEncryption OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 4}
sha-1WithRSAEncryption OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 5}
sha-1WithRSAEncryption OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 5}
signingTime OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 5}
signingTime OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 5}
smimeCapabilities OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 15}
smimeCapabilities OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 15}
B. References
B.参考资料
[3DES] W. Tuchman, "Hellman Presents No Shortcut Solutions To DES," IEEE Spectrum, v. 16, n. 7, July 1979, pp40-41.
[3DES]W.Tuchman，“Hellman没有为DES提供捷径解决方案”，IEEE Spectrum，v。16，n。1979年7月7日，第40-41页。
[CHARSETS] Character sets assigned by IANA. See <ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets>.
[字符集]IANA分配的字符集。看<ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets>.
[CONTDISP] Troost, R., Dorner, S and K. Moore, "Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field", RFC 2183, August 1997.
[CONTDISP]Troost，R.，Dorner，S和K.Moore，“在Internet消息中传递表示信息：内容处置标题字段”，RFC 2183，1997年8月。
[DES] ANSI X3.106, "American National Standard for Information Systems-Data Link Encryption," American National Standards Institute, 1983.
[DES]ANSI X3.106，“美国信息系统数据链路加密国家标准”，美国国家标准协会，1983年。
[MD5] Rivest, R., "The MD5 Message Digest Algorithm", RFC 1321, April 1992.
[MD5]Rivest，R.，“MD5消息摘要算法”，RFC 13211992年4月。
[MIME-SPEC] The primary definition of MIME.
[MIME-SPEC]MIME的主要定义。
Freed, N., and N. Borenstein, "MIME Part 1: Format of Internet Message Bodies", RFC 2045, November 1996.
Freed，N.和N.Borenstein，“MIME第1部分：互联网消息体的格式”，RFC 20451996年11月。
Freed, N., and N. Borenstein, "MIME Part 2: Media Types", RFC 2046, November 1996.
Freed，N.和N.Borenstein，“MIME第2部分：媒体类型”，RFC 20461996年11月。
Moore, K., "MIME Part 3: Message Header Extensions for Non-ASCII Text", RFC 2047, November 1996.
Moore，K.，“MIME第3部分：非ASCII文本的消息头扩展”，RFC 2047，1996年11月。
Freed, N., Klensin, J., and J. Postel, "MIME Part 4: Registration Procedures", RFC 2048, November 1996.
Freed，N.，Klensin，J.和J.Postel，“MIME第4部分：注册程序”，RFC 20481996年11月。
Freed, N., and N. Borenstein, "MIME Part 5: Conformance Criteria and Examples", RFC 2049, November 1996.
Freed，N.和N.Borenstein，“MIME第5部分：一致性标准和示例”，RFC 2049，1996年11月。
[MIME-SECURE] Galvin, J., Murphy, S., Crocker, S., and N. Freed, "Security Multiparts for MIME: Multipart/Signed and Multipart/Encrypted", RFC 1847, October 1995.
[MIME-SECURE]Galvin，J.，Murphy，S.，Crocker，S.，和N.Freed，“MIME的安全多部分：多部分/签名和多部分/加密”，RFC 1847，1995年10月。
[MUSTSHOULD] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[MUSTSHOULD]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[PKCS-1] Kaliski, B., "PKCS #1: RSA Encryption Version 1.5", RFC 2313, March 1998.
[PKCS-1]Kaliski，B.，“PKCS#1:RSA加密版本1.5”，RFC 2313，1998年3月。
[PKCS-7] Kaliski, B., "PKCS #7: Cryptographic Message Syntax Version 1.5", RFC 2315, March 1998.
[PKCS-7]Kaliski，B.，“PKCS#7：加密消息语法版本1.5”，RFC 2315，1998年3月。
[PKCS-10] Kaliski, B., "PKCS #10: Certification Request Syntax Version 1.5", RFC 2314, March 1998.
[PKCS-10]Kaliski，B.，“PKCS#10：认证请求语法版本1.5”，RFC 2314，1998年3月。
[RC2] Rivest, R., "Description of the RC2(r) Encryption Algorithm", RFC 2268, January 1998.
[RC2]Rivest，R.，“RC2（R）加密算法的描述”，RFC 2268，1998年1月。
[SHA1] NIST FIPS PUB 180-1, "Secure Hash Standard," National Institute of Standards and Technology, U.S. Department of Commerce, DRAFT, 31 May 1994.
[SHA1]NIST FIPS PUB 180-1，“安全哈希标准”，美国商务部国家标准与技术研究所，草案，1994年5月31日。
C. Compatibility with Prior Practice in S/MIME
C.与S/MIME先前实践的兼容性
S/MIME was originally developed by RSA Data Security, Inc. Many developers implemented S/MIME agents before this document was published. All S/MIME receiving agents SHOULD make every attempt to interoperate with these earlier implementations of S/MIME.
S/MIME最初由RSA Data Security，Inc.开发。在本文档发布之前，许多开发人员都实现了S/MIME代理。所有S/MIME接收代理都应该尽一切努力与这些早期的S/MIME实现进行互操作。
Some early implementations of S/MIME agents used the following MIME types:
S/MIME代理的一些早期实现使用了以下MIME类型：
application/x-pkcs7-mime application/x-pkcs7-signature application/x-pkcs10
application/x-pkcs7-mime application/x-pkcs7-signature application/x-pkcs10
In each case, the "x-" subtypes correspond to the subtypes described in this document without the "x-".
在每种情况下，“x-”子类型对应于本文档中描述的不带“x-”的子类型。
Early S/MIME documentation had two profiles for encryption: "restricted" and "unrestricted". The difference between these profiles historically came about due to US Government export regulations, as described at the end of this section. It is expected that in the future, there will be few agents that only use the restricted profile.
早期的S/MIME文档有两个加密配置文件：“受限”和“非受限”。如本节末尾所述，历史上这些概况之间的差异是由于美国政府的出口法规造成的。预计在未来，只有少数代理只使用受限配置文件。
Briefly, the restricted profile required the ability to encrypt and decrypt using RSA's trade-secret RC2 algorithm in CBC mode with 40- bit keys. The unrestricted profile required the ability to encrypt and decrypt using RSA's trade-secret RC2 algorithm in CBC mode with 40-bit keys, and to encrypt and decrypt using tripleDES. The restricted profile also had non-mandatory suggestions for other algorithms, but these were not widely implemented.
简单地说，受限配置文件要求能够在CBC模式下使用RSA的商业秘密RC2算法（使用40位密钥）进行加密和解密。不受限制的配置文件要求能够使用RSA的商业秘密RC2算法在CBC模式下使用40位密钥进行加密和解密，并使用三重密钥进行加密和解密。受限配置文件还对其他算法提出了非强制性建议，但这些建议并未得到广泛实施。
It is important to note that many current implementations of S/MIME use the restricted profile.
需要注意的是，当前许多S/MIME实现都使用受限概要文件。
Due to US Government export regulations, an S/MIME agent which supports a strong content encryption algorithm such as DES would not be freely exportable outside of North America. US software manufacturers have been compelled to incorporate an exportable or "restricted" content encryption algorithm in order to create a widely exportable version of their product. S/MIME agents created in the US and intended for US domestic use (or use under special State
由于美国政府的出口规定，支持DES等强内容加密算法的S/MIME代理无法自由出口到北美以外的地区。美国软件制造商被迫采用可出口或“受限”内容加密算法，以创建其产品的广泛出口版本。在美国创建并拟在美国国内使用（或在特殊状态下使用）的S/MIME代理
Department export licenses) can utilize stronger, "unrestricted" content encryption. However, in order to achieve interoperability, such agents need to support whatever exportable algorithm is incorporated in restricted S/MIME agents.
部门出口许可证）可以利用更强的“无限制”内容加密。然而，为了实现互操作性，此类代理需要支持受限S/MIME代理中包含的任何可导出算法。
The RC2 symmetric encryption algorithm has been approved by the US Government for "expedited" export licensing at certain key sizes. Consequently, support for the RC2 algorithm in CBC mode is required for baseline interoperability in all S/MIME implementations. Support for other strong symmetric encryption algorithms such as RC5 CBC, DES CBC and DES EDE3-CBC for content encryption is strongly encouraged where possible.
RC2对称加密算法已获美国政府批准，用于在特定密钥大小下的“快速”出口许可。因此，所有S/MIME实现中的基线互操作性都需要在CBC模式下支持RC2算法。强烈建议尽可能支持其他强对称加密算法，如RC5 CBC、DES CBC和DES EDE3-CBC，用于内容加密。
D. Request for New MIME Subtypes
D.请求新的MIME子类型
To: ietf-types@iana.org
Subject: Registration of MIME media type application/pkcs7-mime
To: ietf-types@iana.org
Subject: Registration of MIME media type application/pkcs7-mime
MIME media type name: application
MIME媒体类型名称：应用程序
MIME subtype name: pkcs7-mime
MIME子类型名称：pkcs7 MIME
Required parameters: none
所需参数：无
Optional parameters: name, filename, smime-type
可选参数：名称、文件名、smime类型
Encoding considerations: Will be binary data, therefore should use base64 encoding
编码注意事项：将是二进制数据，因此应使用base64编码
Security considerations: Described in [PKCS-7]
安全注意事项：如[PKCS-7]所述
Interoperability considerations: Designed to carry data formatted with PKCS-7, as described in [PKCS-7]
互操作性注意事项：设计用于传输使用PKCS-7格式化的数据，如[PKCS-7]中所述
Published specification: RFC 2311
已发布规范：RFC 2311
Applications which use this media type: Secure Internet mail and other secure data transports.
使用此媒体类型的应用程序：安全Internet邮件和其他安全数据传输。
Additional information: File extension(s): .p7m and .p7c Macintosh File Type Code(s):
其他信息：文件扩展名：.p7m和.p7c Macintosh文件类型代码：
Person & email address to contact for further information: Steve Dusse, spock@rsa.com
联系人和电子邮件地址，以获取更多信息：Steve Dusse，spock@rsa.com
Intended usage: COMMON
预期用途：普通
To: ietf-types@iana.org
Subject: Registration of MIME media type application/pkcs7-signature
To: ietf-types@iana.org
Subject: Registration of MIME media type application/pkcs7-signature
MIME media type name: application
MIME媒体类型名称：应用程序
MIME subtype name: pkcs7-signature
MIME子类型名称：pkcs7签名
Required parameters: none
所需参数：无
Optional parameters: name, filename
可选参数：名称、文件名
Encoding considerations: Will be binary data, therefore should use base64 encoding
编码注意事项：将是二进制数据，因此应使用base64编码
Security considerations: Described in [PKCS-7]
安全注意事项：如[PKCS-7]所述
Interoperability considerations: Designed to carry digital signatures with PKCS-7, as described in [PKCS-7]
互操作性注意事项：设计用于携带PKCS-7的数字签名，如[PKCS-7]所述
Published specification: RFC 2311
已发布规范：RFC 2311
Applications which use this media type: Secure Internet mail and other secure data transports.
使用此媒体类型的应用程序：安全Internet邮件和其他安全数据传输。
Additional information: File extension(s): .p7s Macintosh File Type Code(s):
其他信息：文件扩展名：.p7s Macintosh文件类型代码：
Person & email address to contact for further information: Steve Dusse, spock@rsa.com
联系人和电子邮件地址，以获取更多信息：Steve Dusse，spock@rsa.com
Intended usage: COMMON
预期用途：普通
To: ietf-types@iana.org
Subject: Registration of MIME media type application/pkcs10
To: ietf-types@iana.org
Subject: Registration of MIME media type application/pkcs10
MIME media type name: application
MIME媒体类型名称：应用程序
MIME subtype name: pkcs10
MIME子类型名称：pkcs10
Required parameters: none
所需参数：无
Optional parameters: name, filename
可选参数：名称、文件名
Encoding considerations: Will be binary data, therefore should use base64 encoding
编码注意事项：将是二进制数据，因此应使用base64编码
Security considerations: Described in [PKCS-10]
安全注意事项：如[PKCS-10]所述
Interoperability considerations: Designed to carry digital certificates formatted with PKCS-10, as described in [PKCS-10]
互操作性注意事项：设计用于携带使用PKCS-10格式化的数字证书，如[PKCS-10]中所述
Published specification: RFC 2311
已发布规范：RFC 2311
Applications which use this media type: Secure Internet mail and
使用此媒体类型的应用程序：安全Internet邮件和
other transports where certificates are required.
需要证书的其他运输工具。
Additional information: File extension(s): .p10 Macintosh File Type Code(s):
其他信息：文件扩展名：.p10 Macintosh文件类型代码：
Person & email address to contact for further information: Steve Dusse, spock@rsa.com
联系人和电子邮件地址，以获取更多信息：Steve Dusse，spock@rsa.com
Intended usage: COMMON
预期用途：普通
E. Encapsulating Signed Messages for Internet Transport
E.封装用于互联网传输的签名消息
The rationale behind the multiple formats for signing has to do with the MIME subtype defaulting rules of the application and multipart top-level types, and the behavior of currently deployed gateways and mail user agents.
多种签名格式背后的基本原理与应用程序和多部分顶级类型的MIME子类型默认规则以及当前部署的网关和邮件用户代理的行为有关。
Ideally, the multipart/signed format would be the only format used because it provides a truly backwards compatible way to sign MIME entities. In a pure MIME environment with very capable user agents, this would be possible. The world, however, is more complex than this.
理想情况下，多部分/签名格式将是唯一使用的格式，因为它提供了一种真正向后兼容的方式来对MIME实体进行签名。在一个具有非常强大的用户代理的纯MIME环境中，这是可能的。然而，世界比这更复杂。
One problem with the multipart/signed format occurs with gateways to non-MIME environments. In these environments, the gateway will generally not be S/MIME aware, will not recognize the multipart/signed type, and will default its treatment to multipart/mixed as is prescribed by the MIME standard. The real problem occurs when the gateway also applies conversions to the MIME structure of the original message that is being signed and is contained in the first part of the multipart/signed structure, such as the gateway converting text and attachments to the local format. Because the signature is over the MIME structure of the original message, but the original message is now decomposed and transformed, the signature cannot be verified. Because MIME encoding of a particular set of body parts can be done in many different ways, there is no way to reconstruct the original MIME entity over which the signature was computed.
多部分/签名格式的一个问题发生在通往非MIME环境的网关上。在这些环境中，网关通常不支持S/MIME，不会识别多部分/签名类型，并且会按照MIME标准的规定将其处理默认为多部分/混合。当网关还将转换应用于正在签名且包含在多部分/签名结构的第一部分中的原始邮件的MIME结构时，就会出现真正的问题，例如网关将文本和附件转换为本地格式。由于签名位于原始消息的MIME结构之上，但原始消息现在已分解和转换，因此无法验证签名。由于一组特定身体部位的MIME编码可以通过多种不同的方式完成，因此无法重建计算签名的原始MIME实体。
A similar problem occurs when an attempt is made to combine an existing user agent with a stand-alone S/MIME facility. Typical user agents do not have the ability to make a multipart sub-entity available to a stand-alone application in the same way they make leaf MIME entities available to "viewer" applications. This user agent behavior is not required by the MIME standard and thus not widely implemented. The result is that it is impossible for most user agents to hand off the entire multipart/signed entity to a stand-alone application.
当尝试将现有的用户代理与独立的S/MIME功能组合时，也会出现类似的问题。典型的用户代理不具备使多部分子实体可用于独立应用程序的能力，就像它们使叶MIME实体可用于“查看器”应用程序一样。这种用户代理行为不是MIME标准所要求的，因此没有得到广泛的实现。结果是，大多数用户代理不可能将整个多部分/签名实体移交给独立应用程序。
To work around these two problems, the application/pkcs7-mime type can be used. When going through a gateway, it will be defaulted to the MIME type of application/octet-stream and treated as a single opaque entity. That is, the message will be treated as an attachment of unknown type, converted into the local representation for an attachment and thus can be made available to an S/MIME facility completely intact. A similar result is achieved when a user agent
要解决这两个问题，可以使用application/pkcs7 mime类型。当通过网关时，它将默认为应用程序/八位字节流的MIME类型，并被视为单个不透明实体。也就是说，消息将被视为未知类型的附件，转换为附件的本地表示形式，因此可以完全完整地提供给S/MIME设施。当用户代理
similarly treats the application/pkcs7-mime MIME entity as a simple leaf node of the MIME structure and makes it available to viewer applications.
类似地，将application/pkcs7 mime mime实体视为mime结构的简单叶节点，并使其可供查看器应用程序使用。
Another way to work around these problems is to encapsulate the multipart/signed MIME entity in a MIME entity that will not be damaged by the gateway. At the time that this memo is being written, there is a proposal for a MIME entity "application/mime" for this purpose. However, no implementations of S/MIME use this type of wrapping.
解决这些问题的另一种方法是将多部分/签名MIME实体封装在不会被网关损坏的MIME实体中。在编写本备忘录时，有一个MIME实体“application/MIME”的提案。但是，没有任何S/MIME实现使用这种包装。
While this document primarily addresses the Internet, it is useful to compose and receive S/MIME secured messages in non-MIME environments. This is particularly the case when it is desired that security be implemented end-to-end. Other discussion here addresses the receipt of S/MIME messages in non-MIME environments. Here the composition of multipart/signed entities is addressed.
虽然本文档主要针对Internet，但在非MIME环境中编写和接收S/MIME安全消息非常有用。当需要端到端地实现安全性时，情况尤其如此。这里的其他讨论涉及在非MIME环境中接收S/MIME消息。这里讨论了多部分/签名实体的组成。
When a message is to be sent in such an environment, the multipart/signed entity is created as described above. That entity is then treated as an opaque stream of bits and added to the message as an attachment. It must have a file name that ends with ".aps", as this is the sole mechanism for recognizing it as an S/MIME message by the receiving agent.
在这样的环境中发送消息时，如上所述创建多部分/签名实体。然后，该实体被视为不透明的比特流，并作为附件添加到消息中。它必须具有以“.aps”结尾的文件名，因为这是接收代理将其识别为S/MIME消息的唯一机制。
When this message arrives in a MIME environment, it is likely to have a MIME type of application/octet-stream, with MIME parameters giving the filename for the attachment. If the intervening gateway has carried the file type, it will end in ".aps" and be recognized as an S/MIME message.
当此消息到达MIME环境时，它可能具有MIME类型的应用程序/八位字节流，MIME参数提供附件的文件名。如果介入网关携带了文件类型，它将以“.aps”结尾，并被识别为S/MIME消息。
F. Acknowledgements
F.致谢
Significant contributions to the content of this memo were made by many people, including Jim Schaad, Jeff Thompson, and Jeff Weinstein.
许多人对这份备忘录的内容做出了重大贡献，包括吉姆·沙德、杰夫·汤普森和杰夫·温斯坦。
G. Authors' Addresses
G.作者地址
Steve Dusse RSA Data Security, Inc. 100 Marine Parkway, #500 Redwood City, CA 94065 USA
Steve Dusse RSA Data Security，Inc.美国加利福尼亚州红木市500号海洋公园路100号，邮编：94065
Phone: (415) 595-8782 EMail: spock@rsa.com
电话：（415）595-8782电子邮件：spock@rsa.com
Paul Hoffman Internet Mail Consortium 127 Segre Place Santa Cruz, CA 95060
保罗霍夫曼互联网邮件联盟127塞格雷广场圣克鲁斯，加利福尼亚州95060
Phone: (408) 426-9827 EMail: phoffman@imc.org
电话：（408）426-9827电子邮件：phoffman@imc.org
Blake Ramsdell Worldtalk 13122 NE 20th St., Suite C Bellevue, WA 98005
布雷克·拉姆斯代尔世界谈话13122 NE 20 St.，C套房Bellevue，WA 98005
Phone: (425) 882-8861 EMail: blaker@deming.com
电话：（425）882-8861电子邮件：blaker@deming.com
Laurence Lundblade QUALCOMM Incorporated Eudora Division 6455 Lusk Boulevard San Diego, California 92121-2779
Laurence Lundblade高通公司Eudora分部加利福尼亚州圣地亚哥路6455号，邮编92121-2779
Phone: (800) 238-3672 EMail: lgl@qualcomm.com
电话：（800）238-3672电子邮件：lgl@qualcomm.com
Lisa Repka Netscape Communications Corporation 501 East Middlefield Road Mountain View, CA 94043
Lisa Repka Netscape通信公司，加利福尼亚州山景城东米德菲尔德路501号，邮编94043
Phone: (415) 254-1900 EMail: repka@netscape.com
电话：（415）254-1900电子邮件：repka@netscape.com
H. Full Copyright Statement
H.完整的版权声明
Copyright (C) The Internet Society (1998). All Rights Reserved.
版权所有（C）互联网协会（1998年）。版权所有。
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
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The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
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