Signature-in-Signature Verification via a Secure Simple Network Protocol

Handwritten signature is often used for verification of important documents. Attackers can fake someone's handwriting signature in a paper-based document, or deliberately attach someone's handwriting signature in binary image to an electronic document, which may print later, claiming the agreement of the signer. In order to solve this problem, we propose a novel signature-in-signature verification system via a secure simple network protocol. A user (client) sends an electronic document to a signer (server) after initial steps of identity confirmation and key negotiation, then the signer embeds some secure information related to the document and the signer into the handwritten signature. Later the signer sends back the encrypted document together with the fragile watermarked signature. Finally the user stores the document with signature, which can be verified by any third person. Our implementation is a simple UDP-based client-server system with some necessary security functions.