SHA-1, MD5, HMAC Algorithms

This article is all copied from the Internet.

1. SHA-1 and MD5
Md4 (rfc1320) is the ronaldl of MIT. designed in 1990 by Rivest, MD is the abbreviation of messagedigest; MD5 (rfc1321) is an improved version of md4 by Rivest in 1991, and hash any long plaintext into a 128-bit hash value.
Sha1 is designed to be used together with DSA by nist nsa, and Sha is short for secure hash algorithm. It produces a hash value with a length of less than 2 ^ 64 and a length of bits; SHA-1 is designed based on the same principle as md4 and imitates this algorithm.
Information cannot be restored from the message digest; two different messages do not produce the same message digest.

Reference: http://wenda.tianya.cn/wenda/thread? Tid = 7d8ae146f81491e7
Reference: http://blog.csdn.net/candy_whut/archive/2009/02/03/3859830.aspx

2. HMAC
The HMAC algorithm requires a hash algorithm and a key. The implementation of this hash algorithm must meet the requirements of "data is hashed by iterating a basic compression function on blocks of data ".H; Key is shortK.
Hypothesis
BIs the length of blocks (byte) (B = 64 for MD5 and SHA-1 );
LIs the Key Length (byte) (L = 16 for MD5, L = 20 for SHA-1 );
IPad= The byte 0x36 repeated B times;
OPAD= The Byte 0x5c repeated B times;
K can be any length less than or equal to B; if K is greater than B, K = H (k ). It is recommended that the length of K be less than l, otherwise it will reduce the security strength of the algorithm. Formula of this algorithm:H(K XOR OPAD,H (k xor iPad, text)), Where text is the target data, the specific steps:
(1) Add 0 after K to make it length B;
(2) perform bitwise XOR operation on the string (1) generated in bytes B with the iPad;
(3), append to (2) the string of the byte length generated by text streams;
(4), H acts on the streams generated (3;
(5) perform bitwise exclusive or operation on the string generated in bytes B and OPAD;
(6) append to (5) the hash value generated by (4) to a string of B bytes;
(7), H acts on the streams generated by (6.
Reference: rfc2104