A messaging system digitally signs messages to ensure non-repudiation of the sender. Which component should the receiver use to validate the message?

The receiver uses the sender's public key to decrypt and verify the digital signature against the message hash, confirming the message was signed by the claimed sender and has not been altered. This asymmetric relationship - sign with private, verify with public - is the cryptographic foundation of non-repudiation because only the true owner possesses the private key used to produce the signature.

SSL extensions relate to TLS certificate field processing and are not the key component a receiver uses to validate a digital signature.

A negotiated security algorithm describes cipher suite agreement during a TLS handshake, not the specific cryptographic key used to verify a signature.

The private key is held exclusively by the sender to create the signature - it is never shared with or used by the receiver for validation.