The correct answer is RSA. CEH cryptography coverage describes RSA as a widely used asymmetric algorithm that supports encryption and digital signatures and is commonly deployed in public-key infrastructures. The question states that the transaction data is hashed, the hash is signed with the sender’s private key, and the recipient verifies the signature with the matching public key. That is the classic RSA signature model presented in CEH materials. The additional clue is that the same algorithm is said to support encryption, digital signatures, and secure communications use cases. Diffie-Hellman is mainly a key exchange mechanism and is not used for digital signatures in the way described here. DSA is designed for digital signatures, but not for general encryption. ElGamal can support encryption and signatures, but CEH exam framing most strongly associates this full combination of encryption plus digital-signature verification with RSA. CEH references repeatedly emphasize RSA as the standard asymmetric cryptosystem for confidentiality, authentication, integrity, and nonrepudiation in enterprise communications. Because the described implementation combines hashing, private-key signing, and public-key verification within a broad asymmetric framework, RSA is the most accurate answer.