Step by Step Explanation: * Digital signatures provide non-repudiation, ensuring that the sender cannot deny signing a transaction. This mechanism ties the transaction to the entity through cryptographic assurance. * Federation involves identity management and authentication but does not address non-repudiation. * Key escrow is used for securely storing encryption keys and is unrelated to transaction agreements. * Salting hashes enhances password security but does not support transactional non-repudiation. Reference: CASP+ Exam Objectives 2.3 - Apply cryptographic techniques to ensure non-repudiation.