Question

which is a code attached to electronic message to provide its unique identity

Answer 1

 A digital signature is a mathematical scheme for demonstrating the authenticity of a digital message or documents. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, that the sender cannot deny having sent the message (authentication and non-repudiation), and that the message was not altered in transist.

Answer 2

Digital signature

I hope it is correct....