Patent ID: 6912659

Claim:
A method for digitally signing a document utilizing a portable device, comprising the steps of: computing an identification code for the portable device; encoding the identification code into a plurality of analog waves; transmitting the plurality of analog waves from the portable device to a user node; decoding the plurality of analog waves into a digital string; transmitting the document and the digital string from the user node to a recipient node; transmitting the digital string from the recipient node to a third party node; processing the digital string to determine the identification code; identifying the portable device from the identification code; preparing a certificate of identity for the document; transmitting the certificate of identity from the third party node to the recipient nodes; applying a mathematical function to the document to obtain a first result; entering the first result into the portable device; encrypting the first result to obtain a cipher text; wherein the step of encoding comprises encoding the identification code and the cipher text into a plurality of analog waves; wherein the step of processing comprises processing the digital string to determine the cipher text and the identification code; decrypting, at the third party node, the cipher text to determine the first result; wherein the certificate of identity includes the first result; applying, at the recipient node, the mathematical function to the document to obtain a second result; retrieving the first result from the certificate of identity; and comparing the first result to the second result to determine the integrity of the document.