Utente:MiniBill/Sendbox

HMAC

Let:

• H(·) be a cryptographic hash function
• K be a secret key padded to the right with extra zeros to the input block size of the hash function, or the hash of the original key if it's longer than that block size
• m be the message to be authenticated
• ∥ denote concatenation
• ⊕ denote exclusive or (XOR)
• opad be the outer padding (0x5c5c5c…5c5c, one-block-long hexadecimal constant)
• ipad be the inner padding (0x363636…3636, one-block-long hexadecimal constant)

Then HMAC(K,m) is mathematically defined by

HMAC(K,m) = H((K ⊕ opad) ∥ H((K ⊕ ipad) ∥ m)).