Divergence the prime key, the system in order to execute manner, and this manner which verify that it is the key where you can obtain the key divergence in this way from the specified prime key

摘要

PCT No. PCT/FR87/00273 Sec. 371 Date Mar. 10, 1988 Sec. 102(e) Date Mar. 10, 1988 PCT Filed Jul. 9, 1987 PCT Pub. No. WO88/00744 PCT Pub. Date Jan. 28, 1988.The subject of the invention is a method for diversification of a basic key and for authentication of a thus-diversified key as having been fashioned on the basis of a predetermined basic key, and a system for performing the method. An initializing system calculates a diversified key (Sd) on the basis of a basic key (Sb) processed by a biunique combination transformation (T). The key (Sd) recorded in the memory (M3) of a user card (CU3) is authenticated by an exploitation system (4), which calculates a certificate on the basis of the basic key (Sb), while the card (CU3) calculates a certificate on the basis of its key (Sd). These certificates must be identical, taken into account the properties of the transformation (T). The invention is applicable in particular to the secret keys recorded in memory cards.