KDF: key derivation functions

基于password, salt, iterationCount生成key

推荐用 derived_key = PBKDF2(password, salt, iterationCount, derived_key_len)

T_l = F (P, S, c, l)

F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c

U_1 = PRF (P, S || INT (i)) ,
U_2 = PRF (P, U_1) ,
...
U_c = PRF (P, U_{c-1}) 

DK = T_1 || T_2 ||  ...  || T_l<0..r-1>
l = CEIL (dkLen / hLen) #总共要算多少个block
r = dkLen - (l - 1) * hLen #最后一个block取多长

其中，PRF是PseudoRandom Functions，例如HMAC-SHA-1，HMAC-SHA-2

ES: Encryption Scheme

推荐PBES2 Encryption Operation：

已有password，选择PBKDF2, salt, iterationCount, 生成一个derived_key

使用derived_key使用指定加密算法（例如AES-CBC-Pad, RC5-CBC-Pad）加密消息message，获得cipher

MAS: Message Authentication Schemes

推荐使用PBMAC1：

已有password，使用 PBKDF2 生成一个derived_key

使用derived_key 与消息message 作为输入，使用underlying message authentication scheme计算出一个消息验证码T。

MAS函数例如HMAC-SHA-1, HMAC-SHA-2

ASN.1 Syntax

PBKDF2-params ::= SEQUENCE {
       salt CHOICE {
           specified OCTET STRING,
           otherSource AlgorithmIdentifier 
       },
       iterationCount INTEGER (1..MAX),
       keyLength INTEGER (1..MAX) OPTIONAL,
       prf AlgorithmIdentifier  DEFAULT algid-hmacWithSHA1 
       }

PBES2-params ::= SEQUENCE {
      keyDerivationFunc AlgorithmIdentifier ,
      encryptionScheme AlgorithmIdentifier  }

PBES2-KDFs ALGORITHM-IDENTIFIER ::=
      { {PBKDF2-params IDENTIFIED BY id-PBKDF2}, ... }

PBMAC1-params ::=  SEQUENCE {
      keyDerivationFunc AlgorithmIdentifier ,
      messageAuthScheme AlgorithmIdentifier  }