SSCP Systems Security Certified PractitionerCryptographyMedium
A company is designing a system that requires users to digitally sign documents to ensure non-repudiation. Which component of the digital signature process provides the assurance that the signer cannot later deny having signed the document?
- AThe signer's private key
- BThe recipient's public key
- CA hash of the document
- DThe signer's public key
Show answer & explanationAnswer & explanation
Correct answer: A. The signer's private key
The signer's private key is used to create the digital signature. Since only the signer possesses their private key, the act of signing with it proves their identity and subsequently ensures non-repudiation.
Why the other options are wrong
- B. The recipient's public key is irrelevant for the signing process or non-repudiation of the signer.
- C. A hash of the document ensures integrity but doesn't, by itself, provide non-repudiation. It's the hash *encrypted with the private key* that forms the signature.
- D. The signer's public key is used by others to verify the signature, not to create it or ensure non-repudiation directly.
Non-repudiation (Digital Signatures)
The assurance that a party cannot deny the authenticity of their signature on a document or message.
- Achieved by using the signer's unique private key.
- Verifies sender's identity and integrity of data.
- A fundamental security service provided by digital signatures.
Memory trick: Your private key is your unique pen; once you sign, you can't deny it.