RFC5084: Using AES-CCM and AES-GCM Authenticated Encryption in the Cryptographic Message Syntax (CMS)
AES-CCM
输入: key, nonce, plaintext, optional additional authenticated data (AAD)
输出：ciphertext, authentication tag
AAD不会加密传输，只是用于辅助authenticated计算。因此，AAD不在AES-CCM的output内。
CMS authenticated-enveloped-data content type的authenticated属性中包含AAD。
AES-GCM
输入：key, IV, plaintext, optional additional authenticated data (AAD)
输出以及AAD细节与AES-CCM类似
推荐IV长度为12字节
Automated Key Management
需要key Management定期更新AES密钥
CMS authenticated-enveloped-data content type 支持4种key Management技术
- Key Transport: 以接收方的公钥加密content-authenticated-encryption key
- Key Agreement: 以接收方的公钥＋发送方的私钥生成pairwise symmetric key，再用pairwise symmetric key加密content-authenticated-encryption key
- Symmetric Key-Encryption Keys: 以预置的symmetric key-encryption key加密content-authenticated-encryption key
- Passwords: 以password或之前预置的保密信息生成key-encryption key，再用key-encryption key加密content-authenticated-encryption key
