Non-repudiation with digital signatures: how is it achieved?

• A. Non-repudiation is achieved when a digital signature created with a private key binds the signer to the data, verifiable with the signer's public key.
• B. Non-repudiation is achieved by encrypting the entire message with a symmetric key.
• C. Non-repudiation means anyone can deny signing; it doesn't apply to signatures.
• D. Non-repudiation is achieved by hashing only.

Answer: (A)

Non-repudiation with digital signatures is achieved when the signer uses a private key to create a signature over the data, binding the signer to that data. This signature can be verified with the signer’s public key, often tied to an identity via a certificate. Because only the private key holder could have generated the signature, the signer cannot credibly deny signing the data later, and the verification confirms both who signed (via the public key/certificate) and that the data hasn’t been altered. Using symmetric encryption wouldn’t establish who signed since the key is shared among parties, and hashing alone only ensures data integrity without proving signer's identity or involvement.