Patent ID: 8589693
Filing Date: 2013-11-19
Classification: H04L

Abstract:
1. A method of digital signature of a message by a signatory having an identity and making use of a digital signature device on a network, said method using a public-key cryptography scheme and wherein the signatory makes use of a public key and of a first private key and a second private key that belong to the signatory, comprising: generation by the signatory of the first private key on the digital signature device, wherein the first private key is kept in possession of the signatory; generation of the second private key, the second private key being generated, according to the cryptography scheme used, either by the signatory alone, or by a trusted third party with the aid of elements that have been transmitted to the trusted third party by the signatory, wherein the second private key is deposited with the trusted third party; and generation of the public key of the signatory, the public key being generated, according to the cryptography scheme used, either by the signatory alone, or by the trusted third party with the aid of elements that have been transmitted to the trusted third party by the signatory; and for each signature operation, performing the following two complementary steps, each carried out with a distinct private key: calculation by the signatory of a pre-signature of the message with the aid of the signatory's first private key, and the transmission of the message and of the pre-signature to the trusted third party; and verification by the trusted third party of the pre-signature using the second private key and the public key, followed by calculation by the trusted third party of a signature of the message, with the aid of the second private key of the signatory deposited with the trusted third party, and of said pre-signature previously calculated by the signatory.