digitalSignature

Digital signature is a cryptographic technique used to verify the origin, integrity, and, in some cases, non-repudiation of digital data. It typically involves creating a signature with the signer's private key over a cryptographic hash of the data; a recipient verifies the signature using the corresponding public key. By linking the signature to a trusted identity through certificates, digital signatures provide assurance that the data came from the claimed signer and has not been altered.

Public-key cryptography underpins digital signatures. The signer uses a private key to generate the signature, while anyone with access to the signer's public key can verify it. Trust is usually established via a public-key infrastructure (PKI) that binds public keys to real-world identities through digital certificates issued by trusted authorities. Common signing algorithms include RSA, ECDSA, and EdDSA, and signatures can be embedded in formats such as CMS/PKCS#7, XML Digital Signature, or JSON Web Signature (JWS).

Applications span email (S/MIME, PGP), software and code signing, and document signing (PDF, office documents). Benefits include authentication of the signer, data integrity, and non-repudiation, as well as improved workflow security in electronic transactions.

Legal and regulatory perspectives vary by jurisdiction, but many regimes recognize digital signatures as legally equivalent to handwritten signatures when requirements are met (for example, eIDAS in the EU and UETA/ESIGN in the United States). Limitations include key compromise, certificate revocation delays, and potential quantum threats, which motivate practices like certificate management, revocation checks, and timestamping for long-term validity.