Definition
A digital signature binds a message to a signing key through a cryptographic algorithm. Verification uses the corresponding public key and the signed data. In cryptocurrency systems, signatures commonly authorize transfers or other account actions without revealing the private key. A valid signature establishes a relationship to that key; it does not by itself identify the person holding it or prove that the person understood the request.
How It Works
The signer processes the message according to a defined encoding and signature scheme, and a verifier checks the result. Altering the signed data should invalidate the signature under the scheme’s security assumptions. Signatures serve authentication and integrity purposes, whereas encryption primarily protects confidentiality. Signing a public blockchain transaction does not hide its amount or destination, and a signature should not be described simply as encrypting data with a private key.
Key Considerations
Security depends on key protection, correct implementation, and clear binding to the intended action and context. Some schemes require carefully generated per-signature values; implementation mistakes can expose secrets. A malicious website may ask for a technically valid signature that grants an unwanted permission. Review readable details and avoid blind signing where the effect cannot be verified. A compromised key can produce valid signatures, so mathematical validity alone is not a guarantee of legitimate intent, and signing off-chain can still create consequences when another party later submits the authorization.