digital certification method in which a first digital signature dependent upon a first user identity and a first user system in combination , is stored accessibly to a certification server . the first user identity can be distinguished by , for example , a pin provided by the user . subsequently , the user system generates a second signature dependent upon both the current user identity and the current user system in combination . the certifying system then compares the second signature with the first , as stored , to certify the transaction . the certification can accommodate normal computer system component drift . an inquiring system , desiring to confirm the identity of a user , issues a challenge code to the user system . the user system then digests the user &# 39 ; s pin , individual component signatures as they currently exist on the user &# 39 ; s system , together with the challenge code to generate the new signature . the new signature is transmitted back to the inquiring system , which transmits it on to the certification server together with the challenge code . the certification server then digests the challenge code with the original signature as previously stored , and compares the result to the newly provided signature to confirm the users identity , else drift criteria can be applied if desired .