- content, such as a text, image, file, or combination of these, which is appended to an email or message. Examples include favorite quotes, contact information, vCards, or disclaimers. A user may select whether such a signature is included automatically when sending.
- An attachment to an electronic transmission which uniquely identifies and authenticates the sender of a message, file, or other information such as a credit card number. To be effective, a digital signature must not be forged, and measures such as public key cryptography are employed to insure its integrity. Also called digital signature.