What two conditions must a digital signature meet?

Digital signatures rely on asymmetric cryptography: the signer's private key produces a signature that only their corresponding public key can verify, making it unforgeable without key compromise. Authenticity is ensured because only the holder of the private key could have produced the signature, binding identity to the signed content. These two properties are the foundational requirements defined in digital signature standards such as FIPS 186.

Legibility and neatness are physical handwriting attributes and have no meaning in a cryptographic digital signature context.

Digital signatures do not have a 'character count' or 'special character' requirement; their structure is defined by mathematical operations on key pairs.

Digital signatures have no relationship to the length of a physical signature, and 'uniqueness' alone without unforgeability is insufficient as a security property.