There is the natural use for either transmission over an insecure network or for storage on an insecure media. |
Strong Authentication implies that one can prove knowledge of a secret (key) without revealing the key and in particular without sending key between two individuals |
This is effective authentication but requires as many secrets as pairs of people who need to communicate. |
Public key version will only require one key for each individual wishing to be authenticated with anybody else and so is more practical for widespread deployment. N keys and not N2 as for secret key authentication. |
Secret key authentication is however faster and much easier to implement for any sets of sites that wish to establish authenticated communication with a shared secret. |