confidiality: unauthorised person can not access the data
integrity: message is not changed
authetication: verify identity of sender
non repudiation: sender can not deny sending






Hash: sha1 md5

HMAC, a mechanism for message authentication
   using cryptographic hash functions. HMAC can be used with any
   iterative cryptographic hash function, e.g., MD5, SHA-1, in
   combination with a secret shared key. 

 a salt is random data that is used as an additional input to a one-way function that hashes a password or passphrase.