A hash function is any well-defined procedure or mathematical function that converts a large amount of data into a small datum, usually a single integer. For questions about the Twitter and Facebook # symbol, use hashtag
In cryptography, HMAC (Hash-based Message Authentication Code) is a specific construction for calculating a message authentication code (MAC) involving a cryptographic hash function in combination with a secret key.
|Algorithm less susceptible||
"The structure of the hmac algorithm makes it less susceptible to attacks on properties of the underlying hash algorithm"
from question "Why does Chrome display a "SHA1" message with a SHA2 certificate"
"After looking it s seems that hmac is much faster and better in term of security even if the underlying hash function sha1 is broken which is not the case when using rsa-sha1"
from question "In OAuth: use MAC-SHA1 or RSA-SHA1?"
"In some cases on embedded platforms where a fast hash function may not be available these may be more efficient than hmac"
from question "How do you detect that a visitor changed a value in the query string?"
"Hmac is better than a plain hash because it is not vulnerable to hash length extension attacks"
from question "Check if the user changed data"