TLS: Cipher Suites#
简介#
Cipher Suite 在 TLS 中用来指定整个通信过程中所使用的加密相关的参数， 包括如何协商加密得到加密所用的密钥，以及签名使用的算法和哈希算法。
主要涉及到下面几个方面：
- Key exchange (Key 交换算法)
- Bulk encryption （批量加密）
- Message authentication (消息认证)
- Authentication
Key 交换算法 用户交换一个叫做 Shared key 的私钥。 这里主要使用非对称加密算法(asymmetric key algorithm). 这个key 将作为种子，用来生成多个密钥，生成的密钥将用于保护不同的数据。
因为非堆成加密的特性，它只被用来加密少量的数据。 大量数据的情况下，性能会很低，因此不用它来做大数据量的加密操作。
Bulk encryption 用来加密客户端和服务器的通信数据。 不同与非对称加密算法， 这些算法可以用来进行大量数据的加密，而且性能比非对称加密算法强很多。
Message authentication 算法用来生成 消息的哈希，签名等，用来确保消息的完整性。
TLS 中如何协商 Cipher Suite？#
TLS 协议中通过 ClientHello 和 SeverHello 两个包来协商当前链接将要使用的 CipherSuite.
客户端将自己支持的所有 Cipher Suite 的列表，放入 ClientHello 中，发送给服务器端。
服务器端收到 ClientHello 后，从中选择自己也支持的 CipherSuite，然后将选中的结果放在 ServerHello 中发送给客户端。
CipherSuite 列表中，放在最前面的值是客户端最想要的值。
示例#
// ClientHelloTransport Layer Security TLSv1.2 Record Layer: Handshake Protocol: Client Hello Content Type: Handshake (22) ... Handshake Protocol: Client Hello Handshake Type: Client Hello (1) ... Cipher Suites (18 suites) Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (0xc02b) Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f) Cipher Suite: TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (0x009e) Cipher Suite: TLS_RSA_WITH_AES_128_GCM_SHA256 (0x009c) Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA (0xc00a) Cipher Suite: TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (0xc014) Cipher Suite: TLS_DHE_RSA_WITH_AES_256_CBC_SHA (0x0039) Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA (0x0035) Cipher Suite: TLS_ECDHE_ECDSA_WITH_RC4_128_SHA (0xc007) Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA (0xc009) Cipher Suite: TLS_ECDHE_RSA_WITH_RC4_128_SHA (0xc011) Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (0xc013) Cipher Suite: TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x0033) Cipher Suite: TLS_DHE_DSS_WITH_AES_128_CBC_SHA (0x0032) Cipher Suite: TLS_RSA_WITH_RC4_128_SHA (0x0005) Cipher Suite: TLS_RSA_WITH_RC4_128_MD5 (0x0004) Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f) Cipher Suite: TLS_RSA_WITH_3DES_EDE_CBC_SHA (0x000a) Compression Methods Length: 1 Compression Methods (1 method) ... // ServerHelloTransport Layer Security TLSv1.2 Record Layer: Handshake Protocol: Server Hello Content Type: Handshake (22) Version: TLS 1.2 (0x0303) Length: 81 Handshake Protocol: Server Hello Handshake Type: Server Hello (2) Length: 77 Version: TLS 1.2 (0x0303) Random: 8566d75a1... Session ID Length: 32 Session ID: 51ff379f32.... Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f) Compression Method: null (0) Extensions Length: 5 Extension: renegotiation_info (len=1) .... Cipher Suites 示例:#
截止 TLS1.2， 已经有特别多的 CipherSuite 可供选择了。 这里，我们列举一些作为例子：
TLS_RSA_WITH_NULL_SHA256#
Key Exchange: Rivest Shamir Adleman algorithm (RSA)
Authentication: Rivest Shamir Adleman algorithm (RSA)
**Encryption: **NULL Encryption (NULL)
**Hash: **Secure Hash Algorithm 256 (SHA256)
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA#
Key Exchange: Elliptic Curve Diffie-Hellman Ephemeral (ECDHE)
Authentication: Rivest Shamir Adleman algorithm (RSA)
**Encryption: **Advanced Encryption Standard with 128bit key in Cipher Block Chaining mode (AES 128 CBC)
**Hash: **Secure Hash Algorithm 1 (SHA)
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384#
Key Exchange: Elliptic Curve Diffie-Hellman Ephemeral (ECDHE)
Authentication: Elliptic Curve Digital Signature Algorithm (ECDSA)
**Encryption: **Advanced Encryption Standard with 256bit key in Cipher Block Chaining mode (AES 256 CBC)
**Hash: **Secure Hash Algorithm 384 (SHA384)
TLS_AES_256_GCM_SHA384#
Key Exchange: ---
Authentication: ----
**Encryption: **Advanced Encryption Standard with 256bit key in Galois/Counter mode (AES 256 GCM)
**Hash: **Secure Hash Algorithm 384 (SHA384)
TLS_DHE_RSA_WITH_AES_256_CBC_SHA#
Key Exchange: Diffie-Hellman Ephemeral (DHE)
Authentication: Rivest Shamir Adleman algorithm (RSA)
**Encryption: **Advanced Encryption Standard with 256bit key in Cipher Block Chaining mode (AES 256 CBC)
**Hash: **Secure Hash Algorithm 1 (SHA)
TLS_DHE_DSS_WITH_AES_256_CBC_SHA#
Key Exchange: Diffie-Hellman Ephemeral (DHE)
Authentication: Digital Signature Standard (DSS)
**Encryption: **Advanced Encryption Standard with 256bit key in Cipher Block Chaining mode (AES 256 CBC)
**Hash: **Secure Hash Algorithm 1 (SHA)
TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA#
Key Exchange: Diffie-Hellman (DH)
Authentication: Anonymous (anon)
**Encryption: **Data Encryption Standard with 40bit key in Cipher Block Chaining mode (DES40 CBC)
**Hash: **Secure Hash Algorithm 1 (SHA)
TLS_ECDH_ECDSA_WITH_ARIA_128_CBC_SHA256#
Key Exchange: Elliptic Curve Diffie-Hellman (ECDH)
Authentication: Elliptic Curve Digital Signature Algorithm (ECDSA)
**Encryption: **ARIA with 128bit key in Cipher Block Chaining mode (ARIA 128 CBC)
**Hash: **Secure Hash Algorithm 256 (SHA256)