Patent ID: 8433913
Filing Date: 2013-04-30
Classification: H04L

Abstract:
1. A digital signature method for causing a computer to generate a signature for an electronic document, the method comprising: partitioning a target electronic document into a plurality of document segments; initializing a signature t of each of the document segments and twice raising the signature t to the power of a hash value of each of the document segments and digitally signing the raised signature to produce a signature s serving as the signature of the electronic document; and revising a document segment; wherein, in the revising, to delete a document segment, the signature t is raised twice to the power of the hash value of the document segment to be deleted unless the document segment is sanitization prohibited, or the signature t is raised to the power of the hash value of the document to be deleted if the document segment is sanitization prohibited, and the document segment is deleted; to sanitize a document segment, the document segment is replaced with the hash value thereof; to prohibit a document segment from being deleted, the signature t is raised to the power of a double hash value of the document segment to be prohibited from being deleted; and to prohibit a document segment from being sanitized, the signature t is raised to the power of the hash value of the document segment to be prohibited from being sanitized.