Electronic funds transfer system with means for verifying a personal identification number without pre-established secret keys

Claim 1

A method of operating an electronic funds transfer of the type having at least one remote terminal and at least one issuer host terminal, comprising the steps of: (a) accepting at the remote terminal account identification data and a personal identification number PE from a user; (b) providing a first key A at the remote terminal; (c) encrypting PE using encryption key A to derive A(PE); (d) transmitting A(PE) to the host terminal; (e) providing a second key B at the host terminal; (f) encrypting A(PE) at the host terminal using encryption key B to derive B(A[PE]); (g) providing at the host terminal the value of B(PT) which is the correct personal identification number PT encrypted using an encryption key B; (h) transmitting B(A[PE]) and B(PT) from the host terminal to the remote terminal; (i) encrypting B(PT) at the remote terminal using encryption key A to derive the value A(B[PT]); (j) comparing the value of A(B[PT]) to B(A[PE]); (k) executing an electronic funds transaction responsive to the values of A(B[PT]) and B(A[PE]) being the same; wherein each encrypting step is executed with the same algorithm, and wherein the algorithm effects a transformation such that, with two successive encryptions using two different keys the result is the same irrespective of the order of encryption.

Claim 2

A method of operating an electronic funds transfer of the type having at least one remote terminal and at least one issuer host terminal, comprising the steps of: (a) accepting at the remote terminal account identification data and a personal identification number PE from a user; (b) providing a first key A at the remote terminal; (c) encrypting PE using encryption key A to derive A(PE); (d) transmitting A(PE) to the host terminal; (e) providing a second key B at the host terminal; (f) encrypting A(PE) at the host terminal using encryption key B to derive B(A[PE]); (g) providing at the host terminal the value of B(PT) which is the correct personal identification number PT encrypted using an encryption key B; (h) transmitting B(A[PE]) and B(PT) from the host terminal to the remote terminal; (i) encrypting B(PT) at the remote terminal using encryption key A to derive the value A(B[PT]); (j) comparing the value of A(B[PT]) to B(A[PE]); (k) executing an electronic funds transaction responsive to the values of A(B[PT]) and B(A[PE]) being the same; wherein each encrypting step is executed with the same algorithm, and wherein the algorithm effects a transformation such that, with two successive encryptions using two different keys the result is the same irrespective of the order of encryption.