Patent ID: 7430666
Filing Date: 2008-09-30
Classification: H04L

Abstract:
1. A method of authenticating a remote user to a host computer in a data communication system where a remote computer device is used by said remote user, in which said host computer stores a current data string and a current set of verification values, said current set of verification values calculated by said remote computer device using said current data string and a current set of secret keys, said current set of secret keys being chosen and stored by said remote computer device, said method including: at said remote computer device, choosing a next data string and a next set of secret keys, calculating said next set of verification values using said next data string and said next set of secret keys, and calculating a set of check values using said next set of verification values and said current set of secret keys; transmitting said next data string, said next set of verification values and said set of check values in encrypted form from said remote computer device to said host computer; at said host computer, choosing at random, identifiers of a subset of said current set of keys, and obtaining that subset of said current set of keys in encrypted form from said remote computer device; at said host computer, verifying said corresponding subset of said current set of verification values using said current data string and said subset of said current set of keys; then the verification of said corresponding subset of said set of check values using said next data string and said subset of said current set of keys; and the replacement of said current data string and current set of verification values with said next data string and next set of verification values.