1. A method for implementing a digital signature scheme, comprising: obtaining a digital document; embedding, using a processor, a pre-determined number of pairs of data fields in the digital document and filling the pre-determined number of pairs of data fields with filler data according to a pre-determined scheme that is known to signatories of the digital document to arrive at a final digital document having a specified resultant final document size; applying an encrypting hash scheme to the final digital document to obtain a first hash value; encrypting the first hash value using a first encryption key to obtain a first digital signature; substituting a first identifier associated with the first encryption key for the filler data in a first data field of a first pair of the pre-determined number of pairs of data fields in the final digital document; and separately substituting the first digital signature for the filler data in a second data field of the first pair of the pre-determined number of pairs of data fields in the final digital document to obtain a first signed final digital document, the first signed final digital document maintaining a same specified resultant final document size based on the substitutions of the first identifier and the first digital signature separately in the first and second data fields of the first pair of the pre-determined number of pairs of data fields.