This document discusses non-transferable signatures and how they can be implemented using public-key cryptography. It describes how non-transferable signatures allow a message to be signed such that only designated recipients can verify the signature, preserving the privacy of the message. The document provides an example of how Alice can send a signed message to Bob using a random number and their public/private keys. It notes that the authors are working on implementing this technique in Java to allow for different types of non-transferable signatures.