VERIFIABLE CIPHER METHOD, TRANSMITTER TERMINAL, RECEIVER TERMINAL, VERIFIABLE CIPHER SYSTEM AND DATA TRANSMITTING/ RECEIVING METHOD

PROBLEM TO BE SOLVED: To provide a verifiable cipher method in which computational complexity is reduced. SOLUTION: In the verifiable cipher method in which a mobile communication terminal 14 verifies that the user of a mobile communication terminal 12 knows a plaintext corresponding to a cipher text transmitted from the mobile communication terminal, a cipher text e=p* *h+α(mod q) of a plaintext α based on the NTRU public key cipher system and a cipher text a=p*ψ*h+ξ(mod q) of a polynomial ξ are transmitted to the mobile communication terminal 14 by the mobile communication terminal 12 and in response to a polynomial c (challenge) transmitted from the mobile communication terminal 14, polynomials x=ξ+c*α and r=ψ+c* (responses) are transmitted from the mobile communication terminal 12 to the mobile communication terminal 14. In the mobile communication terminal 14, it is verified that both the polynomials (x) and (r) are short polynomials and it is verified that the relationship of a=p*r*h+x-c*e(mod q) is fulfilled. COPYRIGHT: (C)2003,JPO