Patent ID: 8452973

Claim:
A method for generating a digital signature with respect to an electronic document, the method comprising: inputting a target electronic document and a corresponding digital signature σ; dividing the target electronic document into a plurality of partial documents mi; and when a revision of the partial documents of the electronic document is to be performed, in a case where deletion of the one partial document is to be performed, when sanitization is not prohibited, exponentiating the digital signature σ twice with a hash value Gi obtained by using the one partial document to be deleted and a hash function G, when sanitization is prohibited, exponentiating the digital signature with the hash value Gi, and eliminating the partial document to be deleted while taking the hash function G; in a case where sanitization of the one partial document is to be performed, replacing a part corresponding to the one partial document to be sanitized by the hash value Gi obtained by using the one partial document to be sanitized; in a case where deletion of the one partial document is to be prohibited, using a hash function H, which is identical to or different from the hash function G, and exponentiating the digital signature σ with a hash value Hi obtained by using the partial document whose deletion is to be prohibited; in a case where the sanitization of the one partial document is to be prohibited, exponentiating the digital signature G with the hash value Gi obtained by using the one partial document whose sanitization is to be prohibited; and updating the digital signature σ.