What ensures a digital signature's integrity?

The integrity of a digital signature is ensured through the use of encryption technology. This technology employs algorithms that generate unique hash values for the data being signed. When a document is digitally signed, the signature includes this hash value along with the signer's private key, creating a unique digital fingerprint of the document.

When the recipient receives the document, they can use the signer's public key to decrypt the signature and generate a new hash value from the document. If the newly generated hash matches the one embedded in the signature, it confirms that the document has not been altered since it was signed. This process effectively safeguards against any unauthorized changes, thereby maintaining the integrity and authenticity of the digital signature.

The other options do not contribute to ensuring the integrity of a digital signature. Handwritten signatures, witness signatures, and printed documents do not utilize the security features that encryption provides in digital signing.