METHOD FOR TWO STEP DIGITAL SIGNATURE

摘要

The invention relates to a method for the digital signature of a message M by a signer having an identity I and holding a signature device, wherein said method uses a public key cryptographic scheme and is characterised in that the signer has a public key Kp and two private keys Ks and KC, the second private key KC being deposited at a reliable third party, and in that it comprises, for each signing operation, two additional steps each carried out with a separate private key, i.e.: the calculation by the signer of a pre-signature Ss of the message M using the first private key Ks, and transmitting the message M and the pre-signature Ss to the reliable third party; the verification by the reliable third party of the pre-signature Ss followed by the calculation by the reliable third party of a signature S of the message M using the second private key Kc deposited at the reliable third party as well as said pre-signature Ss previously calculated by the signer.