What a digital signature verifies
A digital signature links a message to a private signing key and allows verification with the corresponding public key. Changing the signed data causes verification to fail. The signature supports authenticity and integrity, but connecting that key to a real person or organisation requires an additional basis for trust.
Go deeper
Verify the data and the signing key
A digital-signature system uses a private key to create a signature for data. A verifier uses the corresponding public key to check whether the signature is valid for those exact data.
If the data changes, the original signature should no longer verify. This makes signatures useful for checking that software, documents or messages have not been altered after signing.
A valid signature identifies a key, not automatically a trustworthy human. Certificates, verified exchanges or other arrangements establish whose key it is supposed to be.
- The private key creates signatures.
- The public key checks them.
- The identity-to-key connection needs separate validation.
A signature does not normally make the signed content secret. Anyone allowed to read the data may still do so; confidentiality requires encryption or another access-control mechanism.