CAS-005 practice question 10

A digital signature on an email (for example S/MIME or PGP) is created with the sender's private key, which only the sender holds, so the sender cannot later deny having sent the message, and any change to the message breaks the signature. Non-repudiation is the security feature a signature is specifically used to provide; the signature also proves who signed the message, but that identity proof is what makes non-repudiation possible rather than a separate feature asked for here. Signing does not encrypt the body; that requires encryption with the recipient's public key. Code signing applies to software, and chain of custody is a forensic evidence-handling process.