| 摘要 |
PROBLEM TO BE SOLVED: To enable digital signing with high safety by preventing a sign from being forged. SOLUTION: A sign key (d) is divided into N (integer: N>=2) d1 , dN, etc.; and the signer keeps one of them as a personal key d1 by oneself and stores the remaining N-1 personal keys di (2<=i<=N) as registered keys di at key deposition institutions Pi (2<=i<=N) at N-1 places so that the signer oneself and the key deposition institutions Pi cooperate to digitally sign object data. This digital signing method has a step where the object data are partially signed on a computer of the signer oneself by using the personal key d1 and sent out to the key deposition institutions Pi and a step where the key deposition institutions Pi having received the partially signed object data further partially sign the received partial sign by using the registered keys di that the institutions store and send them out to the computer of the signer oneself or other key deposition institutions Pi.
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