Hash-based Message Authentication Code - Definition (from RFC 2104)

Definition (from RFC 2104)

HMAC (K,m) = H ((Kopad) ∥ H ((Kipad) ∥ m))

where

H is a cryptographic hash function,
K is 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 is the message to be authenticated,
∥ denotes concatenation,
⊕ denotes exclusive or (XOR),
opad is the outer padding (0x5c5c5c…5c5c, one-block-long hexadecimal constant),
and ipad is the inner padding (0x363636…3636, one-block-long hexadecimal constant).

Read more about this topic:  Hash-based Message Authentication Code

Famous quotes containing the word definition:

    ... if, as women, we accept a philosophy of history that asserts that women are by definition assimilated into the male universal, that we can understand our past through a male lens—if we are unaware that women even have a history—we live our lives similarly unanchored, drifting in response to a veering wind of myth and bias.
    Adrienne Rich (b. 1929)