Patent ID: 8422670
Filing Date: 2013-04-16
Classification: H04L

Abstract:
1. A mutual authentication method between a client and a server, processing executed by the server comprising: (a) computing, based on a random number y (yε(Z/qZ)*) generated by the server, a server-side master secret Ks by: (b) receiving first client information U computed by the client from the client together with a first identifier (C, WID, id); (c) computing, using the received first client information U, the first identifier, and a symbol W that represents a part which includes information associated with a password pw, first server information Y by: (d) sending the computed first server information Y to the client; (e) authenticating client authentication information Vc received from the client using the server-side master secret Ks; and (f) generating server authentication information Vs using the server-side master secret Ks, and sending the Vs to the client, where q is an order of a group (G,·), g is a generator of that set G, and “·” is a binary operator on G, the symbol W is allowed to be obtained, based on password information v generated by the client, by: or based on the password information v generated by the client and a committed value T of a random number t generated by the client, by: the password information v is a value computed based on an output of a function H 1 ( ) which has at least the password pw as an input, x is a multiplication on integers, symbol r in equations (2) and (2′) represents a value which is unknown at a time before the client computes the first client information U and a value which is computable by both the server and the client, and U, W, Y, T, gεG, and processing executed by the client comprising: (a′) computing, based on a random number u (uε(Z/qZ)*) generated by the client, the first client information U by: (b′) sending the computed first client information U to the server together with the first identifier; (c′) receiving the first server information Y in response to sending of the first client information U; (d′) when W=g or when W=T (e′) computing, based on the received first server information Y, a client-side master secret Kc by: (f′) generating client authentication information Vc using the client-side master secret Kc, and sending Vc to the server; and (g′) authenticating the server authentication information Vs received from the server using the client-side master secret Kc, where [1/b mod q] indicates an integer a which satisfies [a×b≡1 mod q] and is not less than 1 and is less than q.