Internet Engineering Task Force (IETF)                        Y. Sheffer
Request for Comments: 7525                                        Intuit
BCP: 195                                                         R. Holz
Category: Best Current Practice                                    NICTA
ISSN: 2070-1721                                           P. Saint-Andre
                                                                May 2015
Internet Engineering Task Force (IETF)                        Y. Sheffer
Request for Comments: 7525                                        Intuit
BCP: 195                                                         R. Holz
Category: Best Current Practice                                    NICTA
ISSN: 2070-1721                                           P. Saint-Andre
                                                                May 2015

Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)




Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) are widely used to protect data exchanged over application protocols such as HTTP, SMTP, IMAP, POP, SIP, and XMPP. Over the last few years, several serious attacks on TLS have emerged, including attacks on its most commonly used cipher suites and their modes of operation. This document provides recommendations for improving the security of deployed services that use TLS and DTLS. The recommendations are applicable to the majority of use cases.


Status of This Memo


This memo documents an Internet Best Current Practice.


This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on BCPs is available in Section 2 of RFC 5741.

本文件是互联网工程任务组(IETF)的产品。它代表了IETF社区的共识。它已经接受了公众审查,并已被互联网工程指导小组(IESG)批准出版。有关BCP的更多信息,请参见RFC 5741第2节。

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at


Copyright Notice


Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved.

版权所有(c)2015 IETF信托基金和确定为文件作者的人员。版权所有。

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(自本文件出版之日起生效。请仔细阅读这些文件,因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本,并提供简化BSD许可证中所述的无担保。

Table of Contents


   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  General Recommendations . . . . . . . . . . . . . . . . . . .   5
     3.1.  Protocol Versions . . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  SSL/TLS Protocol Versions . . . . . . . . . . . . . .   5
       3.1.2.  DTLS Protocol Versions  . . . . . . . . . . . . . . .   6
       3.1.3.  Fallback to Lower Versions  . . . . . . . . . . . . .   7
     3.2.  Strict TLS  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Compression . . . . . . . . . . . . . . . . . . . . . . .   8
     3.4.  TLS Session Resumption  . . . . . . . . . . . . . . . . .   8
     3.5.  TLS Renegotiation . . . . . . . . . . . . . . . . . . . .   9
     3.6.  Server Name Indication  . . . . . . . . . . . . . . . . .   9
   4.  Recommendations: Cipher Suites  . . . . . . . . . . . . . . .   9
     4.1.  General Guidelines  . . . . . . . . . . . . . . . . . . .   9
     4.2.  Recommended Cipher Suites . . . . . . . . . . . . . . . .  11
       4.2.1.  Implementation Details  . . . . . . . . . . . . . . .  12
     4.3.  Public Key Length . . . . . . . . . . . . . . . . . . . .  12
     4.4.  Modular Exponential vs. Elliptic Curve DH Cipher Suites .  13
     4.5.  Truncated HMAC  . . . . . . . . . . . . . . . . . . . . .  14
   5.  Applicability Statement . . . . . . . . . . . . . . . . . . .  15
     5.1.  Security Services . . . . . . . . . . . . . . . . . . . .  15
     5.2.  Opportunistic Security  . . . . . . . . . . . . . . . . .  16
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
     6.1.  Host Name Validation  . . . . . . . . . . . . . . . . . .  17
     6.2.  AES-GCM . . . . . . . . . . . . . . . . . . . . . . . . .  18
     6.3.  Forward Secrecy . . . . . . . . . . . . . . . . . . . . .  18
     6.4.  Diffie-Hellman Exponent Reuse . . . . . . . . . . . . . .  19
     6.5.  Certificate Revocation  . . . . . . . . . . . . . . . . .  19
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  21
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  22
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27
   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  General Recommendations . . . . . . . . . . . . . . . . . . .   5
     3.1.  Protocol Versions . . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  SSL/TLS Protocol Versions . . . . . . . . . . . . . .   5
       3.1.2.  DTLS Protocol Versions  . . . . . . . . . . . . . . .   6
       3.1.3.  Fallback to Lower Versions  . . . . . . . . . . . . .   7
     3.2.  Strict TLS  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Compression . . . . . . . . . . . . . . . . . . . . . . .   8
     3.4.  TLS Session Resumption  . . . . . . . . . . . . . . . . .   8
     3.5.  TLS Renegotiation . . . . . . . . . . . . . . . . . . . .   9
     3.6.  Server Name Indication  . . . . . . . . . . . . . . . . .   9
   4.  Recommendations: Cipher Suites  . . . . . . . . . . . . . . .   9
     4.1.  General Guidelines  . . . . . . . . . . . . . . . . . . .   9
     4.2.  Recommended Cipher Suites . . . . . . . . . . . . . . . .  11
       4.2.1.  Implementation Details  . . . . . . . . . . . . . . .  12
     4.3.  Public Key Length . . . . . . . . . . . . . . . . . . . .  12
     4.4.  Modular Exponential vs. Elliptic Curve DH Cipher Suites .  13
     4.5.  Truncated HMAC  . . . . . . . . . . . . . . . . . . . . .  14
   5.  Applicability Statement . . . . . . . . . . . . . . . . . . .  15
     5.1.  Security Services . . . . . . . . . . . . . . . . . . . .  15
     5.2.  Opportunistic Security  . . . . . . . . . . . . . . . . .  16
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
     6.1.  Host Name Validation  . . . . . . . . . . . . . . . . . .  17
     6.2.  AES-GCM . . . . . . . . . . . . . . . . . . . . . . . . .  18
     6.3.  Forward Secrecy . . . . . . . . . . . . . . . . . . . . .  18
     6.4.  Diffie-Hellman Exponent Reuse . . . . . . . . . . . . . .  19
     6.5.  Certificate Revocation  . . . . . . . . . . . . . . . . .  19
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  21
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  22
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27
1. Introduction
1. 介绍

Transport Layer Security (TLS) [RFC5246] and Datagram Transport Security Layer (DTLS) [RFC6347] are widely used to protect data exchanged over application protocols such as HTTP, SMTP, IMAP, POP, SIP, and XMPP. Over the last few years, several serious attacks on TLS have emerged, including attacks on its most commonly used cipher suites and their modes of operation. For instance, both the AES-CBC [RFC3602] and RC4 [RFC7465] encryption algorithms, which together have been the most widely deployed ciphers, have been attacked in the context of TLS. A companion document [RFC7457] provides detailed information about these attacks and will help the reader understand the rationale behind the recommendations provided here.


Because of these attacks, those who implement and deploy TLS and DTLS need updated guidance on how TLS can be used securely. This document provides guidance for deployed services as well as for software implementations, assuming the implementer expects his or her code to be deployed in environments defined in Section 5. In fact, this document calls for the deployment of algorithms that are widely implemented but not yet widely deployed. Concerning deployment, this document targets a wide audience -- namely, all deployers who wish to add authentication (be it one-way only or mutual), confidentiality, and data integrity protection to their communications.


The recommendations herein take into consideration the security of various mechanisms, their technical maturity and interoperability, and their prevalence in implementations at the time of writing. Unless it is explicitly called out that a recommendation applies to TLS alone or to DTLS alone, each recommendation applies to both TLS and DTLS.


It is expected that the TLS 1.3 specification will resolve many of the vulnerabilities listed in this document. A system that deploys TLS 1.3 should have fewer vulnerabilities than TLS 1.2 or below. This document is likely to be updated after TLS 1.3 gets noticeable deployment.

预计TLS 1.3规范将解决本文件中列出的许多漏洞。部署TLS 1.3的系统的漏洞应少于TLS 1.2或更低版本。本文档可能在TLS 1.3部署后更新。

These are minimum recommendations for the use of TLS in the vast majority of implementation and deployment scenarios, with the exception of unauthenticated TLS (see Section 5). Other specifications that reference this document can have stricter requirements related to one or more aspects of the protocol, based on their particular circumstances (e.g., for use with a particular application protocol); when that is the case, implementers are advised to adhere to those stricter requirements. Furthermore, this


document provides a floor, not a ceiling, so stronger options are always allowed (e.g., depending on differing evaluations of the importance of cryptographic strength vs. computational load).


Community knowledge about the strength of various algorithms and feasible attacks can change quickly, and experience shows that a Best Current Practice (BCP) document about security is a point-in-time statement. Readers are advised to seek out any errata or updates that apply to this document.


2. Terminology
2. 术语

A number of security-related terms in this document are used in the sense defined in [RFC4949].


The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].


3. General Recommendations
3. 一般性建议

This section provides general recommendations on the secure use of TLS. Recommendations related to cipher suites are discussed in the following section.


3.1. Protocol Versions
3.1. 协议版本
3.1.1. SSL/TLS Protocol Versions
3.1.1. SSL/TLS协议版本

It is important both to stop using old, less secure versions of SSL/ TLS and to start using modern, more secure versions; therefore, the following are the recommendations concerning TLS/SSL protocol versions:


o Implementations MUST NOT negotiate SSL version 2.

o 实现不得协商SSL版本2。

Rationale: Today, SSLv2 is considered insecure [RFC6176].


o Implementations MUST NOT negotiate SSL version 3.

o 实现不能协商SSL版本3。

Rationale: SSLv3 [RFC6101] was an improvement over SSLv2 and plugged some significant security holes but did not support strong cipher suites. SSLv3 does not support TLS extensions, some of which (e.g., renegotiation_info [RFC5746]) are security-critical. In addition, with the emergence of the POODLE attack [POODLE], SSLv3 is now widely recognized as fundamentally insecure. See [DEP-SSLv3] for further details.


o Implementations SHOULD NOT negotiate TLS version 1.0 [RFC2246]; the only exception is when no higher version is available in the negotiation.

o 实施不应协商TLS 1.0版[RFC2246];唯一的例外是谈判中没有更高版本。

Rationale: TLS 1.0 (published in 1999) does not support many modern, strong cipher suites. In addition, TLS 1.0 lacks a per-record Initialization Vector (IV) for CBC-based cipher suites and does not warn against common padding errors.

理由:TLS 1.0(1999年发布)不支持许多现代的强密码套件。此外,TLS 1.0缺少基于CBC的密码套件的每记录初始化向量(IV),并且没有针对常见填充错误发出警告。

o Implementations SHOULD NOT negotiate TLS version 1.1 [RFC4346]; the only exception is when no higher version is available in the negotiation.

o 实施不应协商TLS 1.1版[RFC4346];唯一的例外是谈判中没有更高版本。

Rationale: TLS 1.1 (published in 2006) is a security improvement over TLS 1.0 but still does not support certain stronger cipher suites.

理由:TLS 1.1(2006年发布)是对TLS 1.0的安全改进,但仍不支持某些更强的密码套件。

o Implementations MUST support TLS 1.2 [RFC5246] and MUST prefer to negotiate TLS version 1.2 over earlier versions of TLS.

o 实施必须支持TLS 1.2[RFC5246],并且必须优先协商TLS版本1.2,而不是TLS的早期版本。

Rationale: Several stronger cipher suites are available only with TLS 1.2 (published in 2008). In fact, the cipher suites recommended by this document (Section 4.2 below) are only available in TLS 1.2.

理由:只有TLS 1.2(于2008年发布)才提供几种更强大的密码套件。事实上,本文件(下文第4.2节)推荐的密码套件仅在TLS 1.2中提供。

This BCP applies to TLS 1.2 and also to earlier versions. It is not safe for readers to assume that the recommendations in this BCP apply to any future version of TLS.

本BCP适用于TLS 1.2和早期版本。读者认为本BCP中的建议适用于任何未来版本的TLS是不安全的。

3.1.2. DTLS Protocol Versions
3.1.2. DTLS协议版本

DTLS, an adaptation of TLS for UDP datagrams, was introduced when TLS 1.1 was published. The following are the recommendations with respect to DTLS:


o Implementations SHOULD NOT negotiate DTLS version 1.0 [RFC4347].

o 实现不应协商DTLS 1.0版[RFC4347]。

Version 1.0 of DTLS correlates to version 1.1 of TLS (see above).


o Implementations MUST support and MUST prefer to negotiate DTLS version 1.2 [RFC6347].

o 实现必须支持DTLS版本1.2[RFC6347],并且必须更愿意协商DTLS版本1.2[RFC6347]。

Version 1.2 of DTLS correlates to version 1.2 of TLS (see above). (There is no version 1.1 of DTLS.)


3.1.3. Fallback to Lower Versions
3.1.3. 回退到较低版本

Clients that "fall back" to lower versions of the protocol after the server rejects higher versions of the protocol MUST NOT fall back to SSLv3 or earlier.


Rationale: Some client implementations revert to lower versions of TLS or even to SSLv3 if the server rejected higher versions of the protocol. This fallback can be forced by a man-in-the-middle (MITM) attacker. TLS 1.0 and SSLv3 are significantly less secure than TLS 1.2, the version recommended by this document. While TLS 1.0-only servers are still quite common, IP scans show that SSLv3-only servers amount to only about 3% of the current Web server population. (At the time of this writing, an explicit method for preventing downgrade attacks has been defined recently in [RFC7507].)

理由:如果服务器拒绝更高版本的协议,一些客户端实现将恢复到更低版本的TLS,甚至恢复到SSLv3。此回退可以由中间人(MITM)攻击者强制执行。TLS 1.0和SSLv3的安全性明显低于本文档推荐的TLS 1.2版本。虽然TLS1.0-only服务器仍然很常见,但IP扫描显示仅SSLv3服务器仅占当前Web服务器总数的3%左右。(在撰写本文时,[RFC7507]最近定义了一种防止降级攻击的显式方法。)

3.2. Strict TLS
3.2. 严格TLS

The following recommendations are provided to help prevent SSL Stripping (an attack that is summarized in Section 2.1 of [RFC7457]):


o In cases where an application protocol allows implementations or deployments a choice between strict TLS configuration and dynamic upgrade from unencrypted to TLS-protected traffic (such as STARTTLS), clients and servers SHOULD prefer strict TLS configuration.

o 如果应用程序协议允许在严格的TLS配置和从未加密到受TLS保护的流量(如STARTTLS)的动态升级之间进行选择,则客户端和服务器应首选严格的TLS配置。

o Application protocols typically provide a way for the server to offer TLS during an initial protocol exchange, and sometimes also provide a way for the server to advertise support for TLS (e.g., through a flag indicating that TLS is required); unfortunately, these indications are sent before the communication channel is encrypted. A client SHOULD attempt to negotiate TLS even if these indications are not communicated by the server.

o 应用程序协议通常为服务器提供在初始协议交换期间提供TLS的方式,有时还为服务器提供播发TLS支持的方式(例如,通过指示需要TLS的标志);不幸的是,这些指示是在通信信道加密之前发送的。即使服务器没有传达这些指示,客户机也应该尝试协商TLS。

o HTTP client and server implementations MUST support the HTTP Strict Transport Security (HSTS) header [RFC6797], in order to allow Web servers to advertise that they are willing to accept TLS-only clients.

o HTTP客户端和服务器实现必须支持HTTP严格传输安全性(HSTS)头[RFC6797],以便允许Web服务器公布它们愿意接受仅TLS客户端。

o Web servers SHOULD use HSTS to indicate that they are willing to accept TLS-only clients, unless they are deployed in such a way that using HSTS would in fact weaken overall security (e.g., it can be problematic to use HSTS with self-signed certificates, as described in Section 11.3 of [RFC6797]).

o Web服务器应使用HST来表示他们愿意接受仅TLS的客户端,除非它们的部署方式使得使用HST实际上会削弱整体安全性(例如,使用带有自签名证书的HST可能有问题,如[RFC6797]第11.3节所述)。

Rationale: Combining unprotected and TLS-protected communication opens the way to SSL Stripping and similar attacks, since an initial part of the communication is not integrity protected and therefore can be manipulated by an attacker whose goal is to keep the communication in the clear.


3.3. Compression
3.3. 压缩

In order to help prevent compression-related attacks (summarized in Section 2.6 of [RFC7457]), implementations and deployments SHOULD disable TLS-level compression (Section 6.2.2 of [RFC5246]), unless the application protocol in question has been shown not to be open to such attacks.


Rationale: TLS compression has been subject to security attacks, such as the CRIME attack.


Implementers should note that compression at higher protocol levels can allow an active attacker to extract cleartext information from the connection. The BREACH attack is one such case. These issues can only be mitigated outside of TLS and are thus outside the scope of this document. See Section 2.6 of [RFC7457] for further details.


3.4. TLS Session Resumption
3.4. TLS会话恢复

If TLS session resumption is used, care ought to be taken to do so safely. In particular, when using session tickets [RFC5077], the resumption information MUST be authenticated and encrypted to prevent modification or eavesdropping by an attacker. Further recommendations apply to session tickets:


o A strong cipher suite MUST be used when encrypting the ticket (as least as strong as the main TLS cipher suite).

o 加密票据时必须使用强密码套件(至少与主TLS密码套件一样强)。

o Ticket keys MUST be changed regularly, e.g., once every week, so as not to negate the benefits of forward secrecy (see Section 6.3 for details on forward secrecy).

o 票证密钥必须定期更换,例如每周更换一次,以免否定前向保密的好处(有关前向保密的详细信息,请参见第6.3节)。

o For similar reasons, session ticket validity SHOULD be limited to a reasonable duration (e.g., half as long as ticket key validity).

o 出于类似原因,会话票证有效期应限制在合理的持续时间内(例如,票证密钥有效期的一半)。

Rationale: session resumption is another kind of TLS handshake, and therefore must be as secure as the initial handshake. This document (Section 4) recommends the use of cipher suites that provide forward secrecy, i.e. that prevent an attacker who gains momentary access to the TLS endpoint (either client or server) and its secrets from reading either past or future communication. The tickets must be managed so as not to negate this security property.


3.5. TLS Renegotiation
3.5. TLS重新谈判

Where handshake renegotiation is implemented, both clients and servers MUST implement the renegotiation_info extension, as defined in [RFC5746].


The most secure option for countering the Triple Handshake attack is to refuse any change of certificates during renegotiation. In addition, TLS clients SHOULD apply the same validation policy for all certificates received over a connection. The [triple-handshake] document suggests several other possible countermeasures, such as binding the master secret to the full handshake (see [SESSION-HASH]) and binding the abbreviated session resumption handshake to the original full handshake. Although the latter two techniques are still under development and thus do not qualify as current practices, those who implement and deploy TLS are advised to watch for further development of appropriate countermeasures.

对抗三重握手攻击最安全的方法是拒绝在重新协商期间更改证书。此外,TLS客户端应为通过连接接收的所有证书应用相同的验证策略。[triple handshake]文档提出了其他几种可能的对策,例如将主密钥绑定到完整握手(请参见[SESSION-HASH]),并将简短的会话恢复握手绑定到原始完整握手。尽管后两种技术仍在开发中,因此不符合当前实践的要求,但建议实施和部署TLS的人员注意适当对策的进一步开发。

3.6. Server Name Indication
3.6. 服务器名称指示

TLS implementations MUST support the Server Name Indication (SNI) extension defined in Section 3 of [RFC6066] for those higher-level protocols that would benefit from it, including HTTPS. However, the actual use of SNI in particular circumstances is a matter of local policy.


Rationale: SNI supports deployment of multiple TLS-protected virtual servers on a single address, and therefore enables fine-grained security for these virtual servers, by allowing each one to have its own certificate.


4. Recommendations: Cipher Suites
4. 建议:密码套件

TLS and its implementations provide considerable flexibility in the selection of cipher suites. Unfortunately, some available cipher suites are insecure, some do not provide the targeted security services, and some no longer provide enough security. Incorrectly configuring a server leads to no or reduced security. This section includes recommendations on the selection and negotiation of cipher suites.


4.1. General Guidelines
4.1. 一般准则

Cryptographic algorithms weaken over time as cryptanalysis improves: algorithms that were once considered strong become weak. Such algorithms need to be phased out over time and replaced with more secure cipher suites. This helps to ensure that the desired security properties still hold. SSL/TLS has been in existence for almost 20


years and many of the cipher suites that have been recommended in various versions of SSL/TLS are now considered weak or at least not as strong as desired. Therefore, this section modernizes the recommendations concerning cipher suite selection.


o Implementations MUST NOT negotiate the cipher suites with NULL encryption.

o 实现不得使用空加密协商密码套件。

Rationale: The NULL cipher suites do not encrypt traffic and so provide no confidentiality services. Any entity in the network with access to the connection can view the plaintext of contents being exchanged by the client and server. (Nevertheless, this document does not discourage software from implementing NULL cipher suites, since they can be useful for testing and debugging.)


o Implementations MUST NOT negotiate RC4 cipher suites.

o 实现不得协商RC4密码套件。

Rationale: The RC4 stream cipher has a variety of cryptographic weaknesses, as documented in [RFC7465]. Note that DTLS specifically forbids the use of RC4 already.


o Implementations MUST NOT negotiate cipher suites offering less than 112 bits of security, including so-called "export-level" encryption (which provide 40 or 56 bits of security).

o 实现不得协商提供少于112位安全性的密码套件,包括所谓的“导出级”加密(提供40或56位安全性)。

Rationale: Based on [RFC3766], at least 112 bits of security is needed. 40-bit and 56-bit security are considered insecure today. TLS 1.1 and 1.2 never negotiate 40-bit or 56-bit export ciphers.

理由:基于[RFC3766],至少需要112位安全性。如今,40位和56位安全性被认为是不安全的。TLS 1.1和1.2从不协商40位或56位导出密码。

o Implementations SHOULD NOT negotiate cipher suites that use algorithms offering less than 128 bits of security.

o 实现不应协商使用安全性低于128位的算法的密码套件。

Rationale: Cipher suites that offer between 112-bits and 128-bits of security are not considered weak at this time; however, it is expected that their useful lifespan is short enough to justify supporting stronger cipher suites at this time. 128-bit ciphers are expected to remain secure for at least several years, and 256-bit ciphers until the next fundamental technology breakthrough. Note that, because of so-called "meet-in-the-middle" attacks [Multiple-Encryption], some legacy cipher suites (e.g., 168-bit 3DES) have an effective key length that is smaller than their nominal key length (112 bits in the case of 3DES). Such cipher suites should be evaluated according to their effective key length.


o Implementations SHOULD NOT negotiate cipher suites based on RSA key transport, a.k.a. "static RSA".

o 实现不应协商基于RSA密钥传输的密码套件,也称为“静态RSA”。

Rationale: These cipher suites, which have assigned values starting with the string "TLS_RSA_WITH_*", have several drawbacks, especially the fact that they do not support forward secrecy.


o Implementations MUST support and prefer to negotiate cipher suites offering forward secrecy, such as those in the Ephemeral Diffie-Hellman and Elliptic Curve Ephemeral Diffie-Hellman ("DHE" and "ECDHE") families.

o 实现必须支持并倾向于协商提供前向保密性的密码套件,如短命Diffie-Hellman和椭圆曲线短命Diffie-Hellman(“DHE”和“ECDHE”)家族中的密码套件。

Rationale: Forward secrecy (sometimes called "perfect forward secrecy") prevents the recovery of information that was encrypted with older session keys, thus limiting the amount of time during which attacks can be successful. See Section 6.3 for a detailed discussion.


4.2. Recommended Cipher Suites
4.2. 推荐密码套件

Given the foregoing considerations, implementation and deployment of the following cipher suites is RECOMMENDED:










These cipher suites are supported only in TLS 1.2 because they are authenticated encryption (AEAD) algorithms [RFC5116].

这些密码套件仅在TLS 1.2中受支持,因为它们是经过身份验证的加密(AEAD)算法[RFC5116]。

Typically, in order to prefer these suites, the order of suites needs to be explicitly configured in server software. (See [BETTERCRYPTO] for helpful deployment guidelines, but note that its recommendations differ from the current document in some details.) It would be ideal if server software implementations were to prefer these suites by default.


Some devices have hardware support for AES-CCM but not AES-GCM, so they are unable to follow the foregoing recommendations regarding cipher suites. There are even devices that do not support public key cryptography at all, but they are out of scope entirely.


4.2.1. Implementation Details
4.2.1. 实施细节

Clients SHOULD include TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 as the first proposal to any server, unless they have prior knowledge that the server cannot respond to a TLS 1.2 client_hello message.

客户机应将TLS_ECDHE_RSA_和_AES_128_GCM_SHA256作为任何服务器的第一个建议,除非他们事先知道服务器无法响应TLS 1.2客户机hello消息。

Servers MUST prefer this cipher suite over weaker cipher suites whenever it is proposed, even if it is not the first proposal.


Clients are of course free to offer stronger cipher suites, e.g., using AES-256; when they do, the server SHOULD prefer the stronger cipher suite unless there are compelling reasons (e.g., seriously degraded performance) to choose otherwise.


This document does not change the mandatory-to-implement TLS cipher suite(s) prescribed by TLS. To maximize interoperability, RFC 5246 mandates implementation of the TLS_RSA_WITH_AES_128_CBC_SHA cipher suite, which is significantly weaker than the cipher suites recommended here. (The GCM mode does not suffer from the same weakness, caused by the order of MAC-then-Encrypt in TLS [Krawczyk2001], since it uses an AEAD mode of operation.) Implementers should consider the interoperability gain against the loss in security when deploying the TLS_RSA_WITH_AES_128_CBC_SHA cipher suite. Other application protocols specify other cipher suites as mandatory to implement (MTI).

本文件不改变实施TLS规定的TLS密码套件的强制性要求。为了最大限度地提高互操作性,RFC 5246要求使用_AES_128_CBC_SHA密码套件实现TLS_RSA_,这明显弱于此处推荐的密码套件。(GCM模式不遭受相同的弱点,这是由于MAC的顺序,然后在TLS[KRAWCZYK2001)中加密,因为它使用AEAD操作模式。当部署TysSyrSaSA使用AES12128CBCSAHA密码套件时,实现者应该考虑互操作增益与安全性损失。其他应用程序协议将其他密码套件指定为强制实现(MTI)。

Note that some profiles of TLS 1.2 use different cipher suites. For example, [RFC6460] defines a profile that uses the TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 and TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 cipher suites.


[RFC4492] allows clients and servers to negotiate ECDH parameters (curves). Both clients and servers SHOULD include the "Supported Elliptic Curves" extension [RFC4492]. For interoperability, clients and servers SHOULD support the NIST P-256 (secp256r1) curve [RFC4492]. In addition, clients SHOULD send an ec_point_formats extension with a single element, "uncompressed".

[RFC4492]允许客户端和服务器协商ECDH参数(曲线)。客户端和服务器都应该包括“受支持的椭圆曲线”扩展[RFC4492]。对于互操作性,客户端和服务器应支持NIST P-256(secp256r1)曲线[RFC4492]。此外,客户端应该发送一个带有单个元素“uncompressed”的ec_point_格式扩展。

4.3. Public Key Length
4.3. 公钥长度

When using the cipher suites recommended in this document, two public keys are normally used in the TLS handshake: one for the Diffie-Hellman key agreement and one for server authentication. Where a client certificate is used, a third public key is added.


With a key exchange based on modular exponential (MODP) Diffie-Hellman groups ("DHE" cipher suites), DH key lengths of at least 2048 bits are RECOMMENDED.


Rationale: For various reasons, in practice, DH keys are typically generated in lengths that are powers of two (e.g., 2^10 = 1024 bits, 2^11 = 2048 bits, 2^12 = 4096 bits). Because a DH key of 1228 bits would be roughly equivalent to only an 80-bit symmetric key [RFC3766], it is better to use keys longer than that for the "DHE" family of cipher suites. A DH key of 1926 bits would be roughly equivalent to a 100-bit symmetric key [RFC3766] and a DH key of 2048 bits might be sufficient for at least the next 10 years [NIST.SP.800-56A]. See Section 4.4 for additional information on the use of MODP Diffie-Hellman in TLS.

理由:出于各种原因,在实践中,DH密钥的生成长度通常为2的幂(例如,2^10=1024位,2^11=2048位,2^12=4096位)。由于1228位的DH密钥大致相当于80位对称密钥[RFC3766],因此最好使用比“DHE”系列密码套件更长的密钥。1926位的DH密钥大致相当于100位对称密钥[RFC3766],2048位的DH密钥至少在未来10年内足够[NIST.SP.800-56A]。有关在TLS中使用MODP Diffie-Hellman的更多信息,请参见第4.4节。

As noted in [RFC3766], correcting for the emergence of a TWIRL machine would imply that 1024-bit DH keys yield about 65 bits of equivalent strength and that a 2048-bit DH key would yield about 92 bits of equivalent strength.


With regard to ECDH keys, the IANA "EC Named Curve Registry" (within the "Transport Layer Security (TLS) Parameters" registry [IANA-TLS]) contains 160-bit elliptic curves that are considered to be roughly equivalent to only an 80-bit symmetric key [ECRYPT-II]. Curves of less than 192 bits SHOULD NOT be used.


When using RSA, servers SHOULD authenticate using certificates with at least a 2048-bit modulus for the public key. In addition, the use of the SHA-256 hash algorithm is RECOMMENDED (see [CAB-Baseline] for more details). Clients SHOULD indicate to servers that they request SHA-256, by using the "Signature Algorithms" extension defined in TLS 1.2.

使用RSA时,服务器应使用公钥的模数至少为2048位的证书进行身份验证。此外,建议使用SHA-256哈希算法(有关更多详细信息,请参阅[CAB基线”)。客户机应使用TLS 1.2中定义的“签名算法”扩展向服务器指示其请求SHA-256。

4.4. Modular Exponential vs. Elliptic Curve DH Cipher Suites
4.4. 模指数与椭圆曲线DH密码套件

Not all TLS implementations support both modular exponential (MODP) and elliptic curve (EC) Diffie-Hellman groups, as required by Section 4.2. Some implementations are severely limited in the length of DH values. When such implementations need to be accommodated, the following are RECOMMENDED (in priority order):


1. Elliptic Curve DHE with appropriately negotiated parameters (e.g., the curve to be used) and a Message Authentication Code (MAC) algorithm stronger than HMAC-SHA1 [RFC5289]

1. 椭圆曲线DHE,具有适当协商的参数(例如,要使用的曲线)和比HMAC-SHA1更强的消息认证码(MAC)算法[RFC5289]

2. TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 [RFC5288], with 2048-bit Diffie-Hellman parameters

2. TLS_DHE_RSA_,带_AES_128_GCM_SHA256[RFC5288],带2048位Diffie-Hellman参数

3. TLS_DHE_RSA_WITH_AES_128_GCM_SHA256, with 1024-bit parameters

3. TLS_DHE_RSA_,带_AES_128_GCM_SHA256,带1024位参数

Rationale: Although Elliptic Curve Cryptography is widely deployed, there are some communities where its adoption has been limited for several reasons, including its complexity compared to modular arithmetic and longstanding perceptions of IPR concerns (which, for the most part, have now been resolved [RFC6090]). Note that ECDHE cipher suites exist for both RSA and ECDSA certificates, so moving to ECDHE cipher suites does not require moving away from RSA-based certificates. On the other hand, there are two related issues hindering effective use of MODP Diffie-Hellman cipher suites in TLS:

理由:尽管椭圆曲线密码术得到了广泛的应用,但在一些社区,由于一些原因,椭圆曲线密码术的应用受到了限制,包括与模块化算法相比的复杂性,以及对IPR问题的长期看法(目前大部分问题已得到解决[RFC6090])。请注意,对于RSA和ECDSA证书,都存在ECDHE密码套件,因此,移动到ECDHE密码套件并不需要离开基于RSA的证书。另一方面,有两个相关问题阻碍了在TLS中有效使用MODP Diffie-Hellman密码套件:

o There are no standardized, widely implemented protocol mechanisms to negotiate the DH groups or parameter lengths supported by client and server.

o 没有标准化、广泛实施的协议机制来协商客户端和服务器支持的DH组或参数长度。

o Many servers choose DH parameters of 1024 bits or fewer.

o 许多服务器选择1024位或更少的DH参数。

o There are widely deployed client implementations that reject received DH parameters if they are longer than 1024 bits. In addition, several implementations do not perform appropriate validation of group parameters and are vulnerable to attacks referenced in Section 2.9 of [RFC7457].

o 广泛部署的客户机实现拒绝接收长度超过1024位的DH参数。此外,一些实现没有对组参数执行适当的验证,并且容易受到[RFC7457]第2.9节中提到的攻击。

Note that with DHE and ECDHE cipher suites, the TLS master key only depends on the Diffie-Hellman parameters and not on the strength of the RSA certificate; moreover, 1024 bit MODP DH parameters are generally considered insufficient at this time.

请注意,对于DHE和ECDHE密码套件,TLS主密钥仅取决于Diffie-Hellman参数,而不取决于RSA证书的强度;此外,1024位MODP DH参数在此时通常被认为是不够的。

With MODP ephemeral DH, deployers ought to carefully evaluate interoperability vs. security considerations when configuring their TLS endpoints.


4.5. Truncated HMAC
4.5. 截断HMAC

Implementations MUST NOT use the Truncated HMAC extension, defined in Section 7 of [RFC6066].


Rationale: the extension does not apply to the AEAD cipher suites recommended above. However it does apply to most other TLS cipher suites. Its use has been shown to be insecure in [PatersonRS11].


5. Applicability Statement
5. 适用性声明

The recommendations of this document primarily apply to the implementation and deployment of application protocols that are most commonly used with TLS and DTLS on the Internet today. Examples include, but are not limited to:


o Web software and services that wish to protect HTTP traffic with TLS.

o 希望通过TLS保护HTTP通信的Web软件和服务。

o Email software and services that wish to protect IMAP, POP3, or SMTP traffic with TLS.

o 希望通过TLS保护IMAP、POP3或SMTP通信的电子邮件软件和服务。

o Instant-messaging software and services that wish to protect Extensible Messaging and Presence Protocol (XMPP) or Internet Relay Chat (IRC) traffic with TLS.

o 希望通过TLS保护可扩展消息和状态协议(XMPP)或Internet中继聊天(IRC)流量的即时消息软件和服务。

o Realtime media software and services that wish to protect Secure Realtime Transport Protocol (SRTP) traffic with DTLS.

o 希望使用DTL保护安全实时传输协议(SRTP)通信的实时媒体软件和服务。

This document does not modify the implementation and deployment recommendations (e.g., mandatory-to-implement cipher suites) prescribed by existing application protocols that employ TLS or DTLS. If the community that uses such an application protocol wishes to modernize its usage of TLS or DTLS to be consistent with the best practices recommended here, it needs to explicitly update the existing application protocol definition (one example is [TLS-XMPP], which updates [RFC6120]).


Designers of new application protocols developed through the Internet Standards Process [RFC2026] are expected at minimum to conform to the best practices recommended here, unless they provide documentation of compelling reasons that would prevent such conformance (e.g., widespread deployment on constrained devices that lack support for the necessary algorithms).


5.1. Security Services
5.1. 安全服务

This document provides recommendations for an audience that wishes to secure their communication with TLS to achieve the following:


o Confidentiality: all application-layer communication is encrypted with the goal that no party should be able to decrypt it except the intended receiver.

o 机密性:所有应用层通信都是加密的,目的是除了预期的接收方之外,任何一方都不能对其进行解密。

o Data integrity: any changes made to the communication in transit are detectable by the receiver.

o 数据完整性:在传输过程中对通信所做的任何更改都可以被接收器检测到。

o Authentication: an endpoint of the TLS communication is authenticated as the intended entity to communicate with.

o 身份验证:TLS通信的端点作为要与之通信的预期实体进行身份验证。

With regard to authentication, TLS enables authentication of one or both endpoints in the communication. In the context of opportunistic security [RFC7435], TLS is sometimes used without authentication. As discussed in Section 5.2, considerations for opportunistic security are not in scope for this document.


If deployers deviate from the recommendations given in this document, they need to be aware that they might lose access to one of the foregoing security services.


This document applies only to environments where confidentiality is required. It recommends algorithms and configuration options that enforce secrecy of the data in transit.


This document also assumes that data integrity protection is always one of the goals of a deployment. In cases where integrity is not required, it does not make sense to employ TLS in the first place. There are attacks against confidentiality-only protection that utilize the lack of integrity to also break confidentiality (see, for instance, [DegabrieleP07] in the context of IPsec).


This document addresses itself to application protocols that are most commonly used on the Internet with TLS and DTLS. Typically, all communication between TLS clients and TLS servers requires all three of the above security services. This is particularly true where TLS clients are user agents like Web browsers or email software.


This document does not address the rarer deployment scenarios where one of the above three properties is not desired, such as the use case described in Section 5.2 below. As another scenario where confidentiality is not needed, consider a monitored network where the authorities in charge of the respective traffic domain require full access to unencrypted (plaintext) traffic, and where users collaborate and send their traffic in the clear.


5.2. Opportunistic Security
5.2. 机会主义安全

There are several important scenarios in which the use of TLS is optional, i.e., the client decides dynamically ("opportunistically") whether to use TLS with a particular server or to connect in the clear. This practice, often called "opportunistic security", is described at length in [RFC7435] and is often motivated by a desire for backward compatibility with legacy deployments.


In these scenarios, some of the recommendations in this document might be too strict, since adhering to them could cause fallback to cleartext, a worse outcome than using TLS with an outdated protocol version or cipher suite.


This document specifies best practices for TLS in general. A separate document containing recommendations for the use of TLS with opportunistic security is to be completed in the future.


6. Security Considerations
6. 安全考虑

This entire document discusses the security practices directly affecting applications using the TLS protocol. This section contains broader security considerations related to technologies used in conjunction with or by TLS.


6.1. Host Name Validation
6.1. 主机名验证

Application authors should take note that some TLS implementations do not validate host names. If the TLS implementation they are using does not validate host names, authors might need to write their own validation code or consider using a different TLS implementation.


It is noted that the requirements regarding host name validation (and, in general, binding between the TLS layer and the protocol that runs above it) vary between different protocols. For HTTPS, these requirements are defined by Section 3 of [RFC2818].


Readers are referred to [RFC6125] for further details regarding generic host name validation in the TLS context. In addition, that RFC contains a long list of example protocols, some of which implement a policy very different from HTTPS.


If the host name is discovered indirectly and in an insecure manner (e.g., by an insecure DNS query for an MX or SRV record), it SHOULD NOT be used as a reference identifier [RFC6125] even when it matches the presented certificate. This proviso does not apply if the host name is discovered securely (for further discussion, see [DANE-SRV] and [DANE-SMTP]).


Host name validation typically applies only to the leaf "end entity" certificate. Naturally, in order to ensure proper authentication in the context of the PKI, application clients need to verify the entire certification path in accordance with [RFC5280] (see also [RFC6125]).


6.2. AES-GCM
6.2. AES-GCM

Section 4.2 above recommends the use of the AES-GCM authenticated encryption algorithm. Please refer to Section 11 of [RFC5246] for general security considerations when using TLS 1.2, and to Section 6 of [RFC5288] for security considerations that apply specifically to AES-GCM when used with TLS.

上文第4.2节建议使用AES-GCM认证加密算法。使用TLS 1.2时的一般安全注意事项请参考[RFC5246]第11节,与TLS一起使用时特别适用于AES-GCM的安全注意事项请参考[RFC5288]第6节。

6.3. Forward Secrecy
6.3. 正向安全

Forward secrecy (also called "perfect forward secrecy" or "PFS" and defined in [RFC4949]) is a defense against an attacker who records encrypted conversations where the session keys are only encrypted with the communicating parties' long-term keys. Should the attacker be able to obtain these long-term keys at some point later in time, the session keys and thus the entire conversation could be decrypted. In the context of TLS and DTLS, such compromise of long-term keys is not entirely implausible. It can happen, for example, due to:


o A client or server being attacked by some other attack vector, and the private key retrieved.

o 客户端或服务器受到其他攻击向量的攻击,并检索私钥。

o A long-term key retrieved from a device that has been sold or otherwise decommissioned without prior wiping.

o 从已出售或未经事先擦拭而退役的设备中检索到的长期密钥。

o A long-term key used on a device as a default key [Heninger2012].

o 在设备上用作默认密钥的长期密钥[Heninger2012]。

o A key generated by a trusted third party like a CA, and later retrieved from it either by extortion or compromise [Soghoian2011].

o 由可信第三方(如CA)生成的密钥,随后通过勒索或妥协从中检索[Soghoian2011]。

o A cryptographic break-through, or the use of asymmetric keys with insufficient length [Kleinjung2010].

o 密码突破,或使用长度不足的非对称密钥[Kleinjung2010]。

o Social engineering attacks against system administrators.

o 针对系统管理员的社会工程攻击。

o Collection of private keys from inadequately protected backups.

o 从保护不充分的备份中收集私钥。

Forward secrecy ensures in such cases that it is not feasible for an attacker to determine the session keys even if the attacker has obtained the long-term keys some time after the conversation. It also protects against an attacker who is in possession of the long-term keys but remains passive during the conversation.


Forward secrecy is generally achieved by using the Diffie-Hellman scheme to derive session keys. The Diffie-Hellman scheme has both parties maintain private secrets and send parameters over the network as modular powers over certain cyclic groups. The properties of the


so-called Discrete Logarithm Problem (DLP) allow the parties to derive the session keys without an eavesdropper being able to do so. There is currently no known attack against DLP if sufficiently large parameters are chosen. A variant of the Diffie-Hellman scheme uses Elliptic Curves instead of the originally proposed modular arithmetics.


Unfortunately, many TLS/DTLS cipher suites were defined that do not feature forward secrecy, e.g., TLS_RSA_WITH_AES_256_CBC_SHA256. This document therefore advocates strict use of forward-secrecy-only ciphers.


6.4. Diffie-Hellman Exponent Reuse
6.4. Diffie-Hellman指数重用

For performance reasons, many TLS implementations reuse Diffie-Hellman and Elliptic Curve Diffie-Hellman exponents across multiple connections. Such reuse can result in major security issues:


o If exponents are reused for too long (e.g., even more than a few hours), an attacker who gains access to the host can decrypt previous connections. In other words, exponent reuse negates the effects of forward secrecy.

o 如果指数重复使用时间过长(例如,甚至超过几个小时),则获得主机访问权限的攻击者可以解密以前的连接。换句话说,指数重用否定了前向保密的效果。

o TLS implementations that reuse exponents should test the DH public key they receive for group membership, in order to avoid some known attacks. These tests are not standardized in TLS at the time of writing. See [RFC6989] for recipient tests required of IKEv2 implementations that reuse DH exponents.

o 重用指数的TLS实现应该测试他们收到的DH公钥的组成员身份,以避免一些已知的攻击。在撰写本文时,这些测试在TLS中没有标准化。有关重用DH指数的IKEv2实现所需的接收方测试,请参见[RFC6989]。

6.5. Certificate Revocation
6.5. 证书撤销

The following considerations and recommendations represent the current state of the art regarding certificate revocation, even though no complete and efficient solution exists for the problem of checking the revocation status of common public key certificates [RFC5280]:


o Although Certificate Revocation Lists (CRLs) are the most widely supported mechanism for distributing revocation information, they have known scaling challenges that limit their usefulness (despite workarounds such as partitioned CRLs and delta CRLs).

o 尽管证书吊销列表(Certificate Revocation list,CRL)是最受广泛支持的分发吊销信息的机制,但它们已知的扩展挑战限制了它们的有用性(尽管存在诸如分区CRL和增量CRL之类的变通方法)。

o Proprietary mechanisms that embed revocation lists in the Web browser's configuration database cannot scale beyond a small number of the most heavily used Web servers.

o 在Web浏览器的配置数据库中嵌入撤销列表的专有机制无法扩展到少数使用最频繁的Web服务器之外。

o The On-Line Certification Status Protocol (OCSP) [RFC6960] presents both scaling and privacy issues. In addition, clients typically "soft-fail", meaning that they do not abort the TLS connection if the OCSP server does not respond. (However, this might be a workaround to avoid denial-of-service attacks if an OCSP responder is taken offline.)

o 在线认证状态协议(OCSP)[RFC6960]提出了扩展和隐私问题。此外,客户端通常为“软故障”,这意味着如果OCSP服务器没有响应,它们不会中止TLS连接。(但是,如果OCSP响应程序脱机,这可能是避免拒绝服务攻击的一种解决方法。)

o The TLS Certificate Status Request extension (Section 8 of [RFC6066]), commonly called "OCSP stapling", resolves the operational issues with OCSP. However, it is still ineffective in the presence of a MITM attacker because the attacker can simply ignore the client's request for a stapled OCSP response.

o TLS证书状态请求扩展(RFC6066)第8节,通常称为“OCSP装订”,解决了OCSP的操作问题。但是,在存在MITM攻击者的情况下,它仍然是无效的,因为攻击者可以简单地忽略客户机对订书机OCSP响应的请求。

o OCSP stapling as defined in [RFC6066] does not extend to intermediate certificates used in a certificate chain. Although the Multiple Certificate Status extension [RFC6961] addresses this shortcoming, it is a recent addition without much deployment.

o [RFC6066]中定义的OCSP装订不扩展到证书链中使用的中间证书。尽管多证书状态扩展[RFC6961]解决了这个缺点,但它是最近添加的,没有进行太多部署。

o Both CRLs and OCSP depend on relatively reliable connectivity to the Internet, which might not be available to certain kinds of nodes (such as newly provisioned devices that need to establish a secure connection in order to boot up for the first time).

o CRL和OCSP都依赖于到Internet的相对可靠的连接,这可能对某些类型的节点(例如需要建立安全连接才能首次启动的新配置设备)不可用。

With regard to common public key certificates, servers SHOULD support the following as a best practice given the current state of the art and as a foundation for a possible future solution:


1. OCSP [RFC6960]

1. OCSP[RFC6960]

2. Both the status_request extension defined in [RFC6066] and the status_request_v2 extension defined in [RFC6961] (This might enable interoperability with the widest range of clients.)

2. [RFC6066]中定义的状态请求扩展和[RFC6961]中定义的状态请求v2扩展(这可以实现与最广泛的客户端的互操作性)

3. The OCSP stapling extension defined in [RFC6961]

3. [RFC6961]中定义的OCSP装订扩展

The considerations in this section do not apply to scenarios where the DANE-TLSA resource record [RFC6698] is used to signal to a client which certificate a server considers valid and good to use for TLS connections.


7. References
7. 工具书类
7.1. Normative References
7.1. 规范性引用文件

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997, <>.

[RFC2119]Bradner,S.,“RFC中用于表示需求水平的关键词”,BCP 14,RFC 2119,1997年3月<>.

[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000, <>.

[RFC2818]Rescorla,E.,“TLS上的HTTP”,RFC 28182000年5月<>.

[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For Public Keys Used For Exchanging Symmetric Keys", BCP 86, RFC 3766, April 2004, <>.

[RFC3766]Orman,H.和P.Hoffman,“确定用于交换对称密钥的公钥的强度”,BCP 86,RFC 3766,2004年4月<>.

[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites for Transport Layer Security (TLS)", RFC 4492, May 2006, <>.

[RFC4492]Blake Wilson,S.,Bolyard,N.,Gupta,V.,Hawk,C.,和B.Moeller,“用于传输层安全(TLS)的椭圆曲线密码(ECC)密码套件”,RFC 4492,2006年5月<>.

[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", FYI 36, RFC 4949, August 2007, <>.

[RFC4949]Shirey,R.,“互联网安全词汇表,第2版”,FYI 36,RFC 49492007年8月<>.

[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008, <>.

[RFC5246]Dierks,T.和E.Rescorla,“传输层安全(TLS)协议版本1.2”,RFC 5246,2008年8月<>.

[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois Counter Mode (GCM) Cipher Suites for TLS", RFC 5288, August 2008, <>.

[RFC5288]Salowey,J.,Choudhury,A.,和D.McGrew,“用于TLS的AES伽罗瓦计数器模式(GCM)密码套件”,RFC 5288,2008年8月<>.

[RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-256/384 and AES Galois Counter Mode (GCM)", RFC 5289, August 2008, <>.

[RFC5289]Rescorla,E.“具有SHA-256/384和AES伽罗瓦计数器模式(GCM)的TLS椭圆曲线密码套件”,RFC 5289,2008年8月<>.

[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov, "Transport Layer Security (TLS) Renegotiation Indication Extension", RFC 5746, February 2010, <>.

[RFC5746]Rescorla,E.,Ray,M.,Dispensa,S.,和N.Oskov,“传输层安全(TLS)重新协商指示扩展”,RFC 57462010年2月<>.

[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS) Extensions: Extension Definitions", RFC 6066, January 2011, <>.

[RFC6066]Eastlake 3rd,D.,“传输层安全(TLS)扩展:扩展定义”,RFC 6066,2011年1月<>.

[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)", RFC 6125, March 2011, <>.

[RFC6125]Saint Andre,P.和J.Hodges,“在传输层安全(TLS)环境下使用X.509(PKIX)证书在互联网公钥基础设施中表示和验证基于域的应用程序服务标识”,RFC 61252011年3月<>.

[RFC6176] Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer (SSL) Version 2.0", RFC 6176, March 2011, <>.

[RFC6176]Turner,S.和T.Polk,“禁止安全套接字层(SSL)2.0版”,RFC 61762011年3月<>.

[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, January 2012, <>.

[RFC6347]Rescorla,E.和N.Modadugu,“数据报传输层安全版本1.2”,RFC 6347,2012年1月<>.

[RFC7465] Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465, February 2015, <>.

[RFC7465]波波夫,A.“禁止RC4密码套件”,RFC 7465,2015年2月<>.

7.2. Informative References
7.2. 资料性引用

[BETTERCRYPTO], "Applied Crypto Hardening", April 2015, < applied-crypto-hardening.pdf>.

[BETTERCRYPTO],“应用加密加固”,2015年4月< 应用加密强化。pdf>。

[CAB-Baseline] CA/Browser Forum, "Baseline Requirements for the Issuance and Management of Publicly-Trusted Certificates Version 1.1.6", 2013, <>.


[DANE-SMTP] Dukhovni, V. and W. Hardaker, "SMTP security via opportunistic DANE TLS", Work in Progress, draft-ietf-dane-smtp-with-dane-16, April 2015.

[DANE-SMTP]Dukhovni,V.和W.Hardaker,“通过机会主义DANE TLS的SMTP安全”,正在进行的工作,草稿-ietf-DANE-SMTP-with-DANE-162015年4月。

[DANE-SRV] Finch, T., Miller, M., and P. Saint-Andre, "Using DNS-Based Authentication of Named Entities (DANE) TLSA Records with SRV Records", Work in Progress, draft-ietf-dane-srv-14, April 2015.

[DANE-SRV]Finch,T.,Miller,M.,和P.Saint Andre,“使用基于DNS的身份验证命名实体(DANE)TLSA记录和SRV记录”,正在进行的工作,草案-ietf-DANE-SRV-14,2015年4月。

[DEP-SSLv3] Barnes, R., Thomson, M., Pironti, A., and A. Langley, "Deprecating Secure Sockets Layer Version 3.0", Work in Progress, draft-ietf-tls-sslv3-diediedie-03, April 2015.


[DegabrieleP07] Degabriele, J. and K. Paterson, "Attacking the IPsec Standards in Encryption-only Configurations", IEEE Symposium on Security and Privacy (SP '07), 2007, <>.


[ECRYPT-II] Smart, N., "ECRYPT II Yearly Report on Algorithms and Keysizes (2011-2012)", 2012, <>.

[ECRYPT-II]斯马特,N.,“ECRYPT II算法和密钥设置年度报告(2011-2012)”,2012年<>.

[Heninger2012] Heninger, N., Durumeric, Z., Wustrow, E., and J. Halderman, "Mining Your Ps and Qs: Detection of Widespread Weak Keys in Network Devices", Usenix Security Symposium 2012, 2012.

[Heninger 2012]Heninger,N.,Durumeric,Z.,Wustrow,E.,和J.Halderman,“挖掘您的Ps和Qs:检测网络设备中广泛存在的弱密钥”,Usenix安全研讨会2012,2012年。

[IANA-TLS] IANA, "Transport Layer Security (TLS) Parameters", <>.


[Kleinjung2010] Kleinjung, T., "Factorization of a 768-Bit RSA modulus", CRYPTO 10, 2010, <>.

[Kleinjung2010]Kleinjung,T.,“768位RSA模的因式分解”,CRYPTO 10,2010<>.

[Krawczyk2001] Krawczyk, H., "The Order of Encryption and Authentication for Protecting Communications (Or: How Secure is SSL?)", CRYPTO 01, 2001, <>.

[Krawczyk2001]Krawczyk,H.,“保护通信的加密和身份验证顺序(或:SSL有多安全?)”,CRYPTO 01,2001<>.

[Multiple-Encryption] Merkle, R. and M. Hellman, "On the security of multiple encryption", Communications of the ACM, Vol. 24, 1981, <>.


[NIST.SP.800-56A] Barker, E., Chen, L., Roginsky, A., and M. Smid, "Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography", NIST Special Publication 800-56A, 2013, < NIST.SP.800-56Ar2.pdf>.

[NIST.SP.800-56A]Barker,E.,Chen,L.,Roginsky,A.,和M.Smid,“使用离散对数加密的成对密钥建立方案的建议”,NIST特别出版物800-56A,2013年< NIST.SP.800-56Ar2.pdf>。

[POODLE] US-CERT, "SSL 3.0 Protocol Vulnerability and POODLE Attack", Alert TA14-290A, October 2014, <>.

[POODLE]US-CERT,“SSL 3.0协议漏洞和POODLE攻击”,警报TA14-290A,2014年10月<>.

[PatersonRS11] Paterson, K., Ristenpart, T., and T. Shrimpton, "Tag size does matter: attacks and proofs for the TLS record protocol", 2011, <>.


[RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996, <>.

[RFC2026]Bradner,S.,“互联网标准过程——第3版”,BCP 9,RFC 2026,1996年10月<>.

[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999, <>.


[RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher Algorithm and Its Use with IPsec", RFC 3602, September 2003, <>.

[RFC3602]Frankel,S.,Glenn,R.,和S.Kelly,“AES-CBC密码算法及其在IPsec中的使用”,RFC 3602,2003年9月<>.

[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006, <>.

[RFC4346]Dierks,T.和E.Rescorla,“传输层安全(TLS)协议版本1.1”,RFC 4346,2006年4月<>.

[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security", RFC 4347, April 2006, <>.

[RFC4347]Rescorla,E.和N.Modadugu,“数据报传输层安全”,RFC 4347,2006年4月<>.

[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, "Transport Layer Security (TLS) Session Resumption without Server-Side State", RFC 5077, January 2008, <>.

[RFC5077]Salowey,J.,Zhou,H.,Eronen,P.,和H.Tschofenig,“无服务器端状态的传输层安全(TLS)会话恢复”,RFC 5077,2008年1月<>.

[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated Encryption", RFC 5116, January 2008, <>.

[RFC5116]McGrew,D.“认证加密的接口和算法”,RFC 5116,2008年1月<>.

[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, May 2008, <>.

[RFC5280]Cooper,D.,Santesson,S.,Farrell,S.,Boeyen,S.,Housley,R.,和W.Polk,“Internet X.509公钥基础设施证书和证书撤销列表(CRL)配置文件”,RFC 52802008年5月<>.

[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic Curve Cryptography Algorithms", RFC 6090, February 2011, <>.

[RFC6090]McGrew,D.,Igoe,K.,和M.Salter,“基本椭圆曲线密码算法”,RFC 60902011年2月<>.

[RFC6101] Freier, A., Karlton, P., and P. Kocher, "The Secure Sockets Layer (SSL) Protocol Version 3.0", RFC 6101, August 2011, <>.

[RFC6101]Freier,A.,Karlton,P.,和P.Kocher,“安全套接字层(SSL)协议版本3.0”,RFC 61012011年8月<>.

[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Core", RFC 6120, March 2011, <>.

[RFC6120]Saint Andre,P.,“可扩展消息和状态协议(XMPP):核心”,RFC61202011年3月<>.

[RFC6460] Salter, M. and R. Housley, "Suite B Profile for Transport Layer Security (TLS)", RFC 6460, January 2012, <>.

[RFC6460]Salter,M.和R.Housley,“传输层安全(TLS)的套件B配置文件”,RFC 64602012年1月<>.

[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA", RFC 6698, August 2012, <>.

[RFC6698]Hoffman,P.和J.Schlyter,“基于DNS的命名实体认证(DANE)传输层安全(TLS)协议:TLSA”,RFC 6698,2012年8月<>.

[RFC6797] Hodges, J., Jackson, C., and A. Barth, "HTTP Strict Transport Security (HSTS)", RFC 6797, November 2012, <>.

[RFC6797]Hodges,J.,Jackson,C.,和A.Barth,“HTTP严格传输安全(HSTS)”,RFC 67972012年11月<>.

[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A., Galperin, S., and C. Adams, "X.509 Internet Public Key Infrastructure Online Certificate Status Protocol - OCSP", RFC 6960, June 2013, <>.

[RFC6960]Santesson,S.,Myers,M.,Ankney,R.,Malpani,A.,Galperin,S.,和C.Adams,“X.509互联网公钥基础设施在线证书状态协议-OCSP”,RFC 69602013年6月<>.

[RFC6961] Pettersen, Y., "The Transport Layer Security (TLS) Multiple Certificate Status Request Extension", RFC 6961, June 2013, <>.

[RFC6961]Pettersen,Y.,“传输层安全(TLS)多证书状态请求扩展”,RFC 69612013年6月<>.

[RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman Tests for the Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 6989, July 2013, <>.

[RFC6989]Sheffer,Y.和S.Fluhrer,“互联网密钥交换协议版本2(IKEv2)的附加Diffie-Hellman测试”,RFC 69892013年7月<>.

[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection Most of the Time", RFC 7435, December 2014, <>.

[RFC7435]Dukhovni,V.,“机会主义安全:大部分时间的一些保护”,RFC 7435,2014年12月<>.

[RFC7457] Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing Known Attacks on Transport Layer Security (TLS) and Datagram TLS (DTLS)", RFC 7457, February 2015, <>.

[RFC7457]Sheffer,Y.,Holz,R.,和P.Saint Andre,“总结对传输层安全(TLS)和数据报TLS(DTLS)的已知攻击”,RFC 7457,2015年2月<>.

[RFC7507] Moeller, B. and A. Langley, "TLS Fallback Signaling Cipher Suite Value (SCSV) for Preventing Protocol Downgrade Attacks", RFC 7507, April 2015.

[RFC7507]Moeller,B.和A.Langley,“用于防止协议降级攻击的TLS回退信令密码套件值(SCSV)”,RFC 7507,2015年4月。

[SESSION-HASH] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A., Langley, A., and M. Ray, "Transport Layer Security (TLS) Session Hash and Extended Master Secret Extension", Work in Progress, draft-ietf-tls-session-hash-05, April 2015.


[Smith2013] Smith, B., "Proposal to Change the Default TLS Ciphersuites Offered by Browsers.", 2013, <>.


[Soghoian2011] Soghoian, C. and S. Stamm, "Certified lies: Detecting and defeating government interception attacks against SSL", Proc. 15th Int. Conf. Financial Cryptography and Data Security, 2011.

[Soghoian 2011]Soghoian,C.和S.Stamm,“经证实的谎言:检测并击败针对SSL的政府拦截攻击”,Proc。第15届国际会议,金融加密和数据安全,2011年。

[TLS-XMPP] Saint-Andre, P. and a. alkemade, "Use of Transport Layer Security (TLS) in the Extensible Messaging and Presence Protocol (XMPP)", Work in Progress, draft-ietf-uta-xmpp-07, April 2015.


[triple-handshake] Delignat-Lavaud, A., Bhargavan, K., and A. Pironti, "Triple Handshakes Considered Harmful: Breaking and Fixing Authentication over TLS", 2014, <>.

[三次握手]Delignat Lavaud,A.,Bhargavan,K.,和A.Pironti,“认为有害的三次握手:破坏和修复TLS认证”,2014年<>.



Thanks to RJ Atkinson, Uri Blumenthal, Viktor Dukhovni, Stephen Farrell, Daniel Kahn Gillmor, Paul Hoffman, Simon Josefsson, Watson Ladd, Orit Levin, Ilari Liusvaara, Johannes Merkle, Bodo Moeller, Yoav Nir, Massimiliano Pala, Kenny Paterson, Patrick Pelletier, Tom Ritter, Joe St. Sauver, Joe Salowey, Rich Salz, Brian Smith, Sean Turner, and Aaron Zauner for their feedback and suggested improvements. Thanks also to Brian Smith, who has provided a great resource in his "Proposal to Change the Default TLS Ciphersuites Offered by Browsers" [Smith2013]. Finally, thanks to all others who commented on the TLS, UTA, and other discussion lists but who are not mentioned here by name.

感谢RJ Atkinson、Uri Blumenthal、Viktor Dukhovni、Stephen Farrell、Daniel Kahn Gillmor、Paul Hoffman、Simon Josefsson、Watson Ladd、Orit Levin、Ilari Liusvaara、Johannes Merkle、Bodo Moeller、Yoav Nir、Massimiliano Pala、Kenny Paterson、Patrick Pelletier、Tom Ritter、Joe St.Sauver、Joe Salowey、Rich Salz、Brian Smith、Sean Turner、,和Aaron Zauner听取了他们的反馈并提出了改进建议。还要感谢Brian Smith,他在其“更改浏览器提供的默认TLS密码套件的提案”[Smith2013]中提供了大量资源。最后,感谢所有对TLS、UTA和其他讨论列表发表评论但此处未提及姓名的其他人。

Robert Sparks and Dave Waltermire provided helpful reviews on behalf of the General Area Review Team and the Security Directorate, respectively.

罗伯特·斯帕克斯(Robert Sparks)和戴夫·沃尔特米尔(Dave Waltermire)分别代表总区域审查小组和安全理事会提供了有用的审查。

During IESG review, Richard Barnes, Alissa Cooper, Spencer Dawkins, Stephen Farrell, Barry Leiba, Kathleen Moriarty, and Pete Resnick provided comments that led to further improvements.

在IESG审查期间,Richard Barnes、Alissa Cooper、Spencer Dawkins、Stephen Farrell、Barry Leiba、Kathleen Moriarty和Pete Resnick提供了意见,这些意见导致了进一步的改进。

Ralph Holz gratefully acknowledges the support by Technische Universitaet Muenchen. The authors gratefully acknowledge the assistance of Leif Johansson and Orit Levin as the working group chairs and Pete Resnick as the sponsoring Area Director.

拉尔夫·霍尔茨感谢慕尼黑理工大学的支持。作者衷心感谢Leif Johansson和Orit Levin担任工作组主席,Pete Resnick担任赞助区域主任的协助。

Authors' Addresses


Yaron Sheffer Intuit 4 HaHarash St. Hod HaSharon 4524075 Israel

Yaron Sheffer Intuit 4 HaHarash St.Hod HaSharon 4524075以色列


Ralph Holz NICTA 13 Garden St. Eveleigh 2015 NSW Australia

Ralph Holz NICTA 13 Garden St.Eveleigh 2015澳大利亚新南威尔士州


Peter Saint-Andre &yet