Method of generating DSA signatures from portable devices at low cost.

Method of generating DSA digital signatures from portable type devices A1, A2, Ai..An circuit card type integrated microprocessor, comprising calculation means, communication and data retention, which comprise at least one nonvolatile memory electrically programmable, hereinafter referred to as EEPROM, in which fits a key-card itself to each card and represents the key of the DES algorithm, this method comprises the following steps: - preparation of encrypted data constituting coupons J, ro J, x. - loading these coupons in the non-volatile memories, - and using these coupons to sign a message received from a certified B or verifier central authority, the preparation is made from a random number J removed by this authority B or by the card, which is stored in reduced form Z1 bytes, and is exploited in calculations as a number i obtained by expansion of J to Z2 bytes.