Password authentication schemes with smart cards

In this paper, two password authentication schemes with smart cards are pro posed. In the schemes, users can change their pass-words freely, and the re mote system does nor need the directory of passwords or verification tables to authenticate users. Once the secure network environment is see up, auth entication can be handled solely by the two parries involved. For a network without synchronized clocks, the proposed nonce-based authentication schem e is able to prevent malicious reply attacks.