Which of the following best describes how to sign a document using a digital signature?
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Create a hash of the document and encrypt the resulting hash using the signer's private key
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Encrypt the document using the signer's private key
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Encrypt the document using the signer's private key and create a hash of the encrypted document
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Encrypt the document using the signer's public key
Digital signatures work by creating a hash of the original document, then encrypting that hash with the signer's private key. This creates a fixed-size signature that can be verified by decrypting with the public key and comparing against a newly computed hash. The document itself isn't encrypted (options B, C, D) - digital signatures provide authenticity and integrity, not confidentiality.
Correct. A digital signature is created by first computing a cryptographic hash (digest) of the document, then encrypting that hash with the signer's private key — the encrypted hash is the signature, appended to (or sent alongside) the document. The recipient verifies it by hashing the received document themselves, decrypting the signature using the signer's public key, and checking the two hashes match — this proves both authenticity (only the private-key holder could have produced it) and integrity (any change to the document changes its hash). Encrypting the whole document with the private key (options b/c) would be extremely inefficient for large documents and isn't how signature schemes work, and encrypting with the signer's public key (option d) is backwards — that would mean only the signer could decrypt it, which is useless for verification by others.