US Patent 9614681 Private electronic signature service for electronic documents

Techniques are disclosed for providing an electronic signature service where the content of an electronic document to be signed remains unknown to the service. A sender of the electronic document negotiates a specification for encoding the electronic document. In particular, the specification does not include any content of the electronic document. In this manner, the content of the electronic document can be encrypted and securely transmitted between the sender and the signer via the electronic signature service using one or more data packets conforming to the specification without permitting the electronic signature service to read or otherwise decipher the content. The specification enables the electronic signature service to certify that the signer has received the electronic document and assented to its terms. Further, the specification enables the electronic signature service to perform authentication and transaction logging operations associated with obtaining an electronically signed version of the electronic document.