To provide an electronic signature method which prevents the increase of data size of digital data by deleting invalidated electronic signatures, protects and authenticates digital time stamps executed on the digital data over a term of validity in a multiplex electronic signature constituted of a plurality of electronic signatures executed to one piece of digital data.

At the time of executing the electronic signature to the digital data 40 first, a plurality of electronic signature embedding areas (slots 51, 52 and 53) are preliminarily created and each embedding area is made to have the recognition of the existence of the electronic signatures, their contents or marks to make an embedded order. In addition, the electronic signature does not set other electronic signatures as objects of digest values more than required.

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