Signature

The term signature refers to two unrelated concepts in software, distinguished only by context.

In programming, a signature is a synonym for a function signature — the part of a function or method’s declaration that defines how it can be called, without saying anything about what it does internally.

In security, a digital signature is a cryptographic mechanism for proving that a piece of data was created by a specific party and has not been altered since. It’s typically produced with asymmetric cryptography. The signer computes a hash of the data and encrypts it with their private key, and anyone holding the corresponding public key can verify the signature against the data. This gives a recipient authenticity and non-repudiation — the signer cannot later deny having produced it — alongside evidence that the data itself is intact.