When transmitting a payment instruction, which of the following will help verify that the instruction was not duplicated?

A. Use of a cryptographic hashing algorithm

B. Enciphering the message digest

C. Deciphering the message digest

D. A sequence number and time stamp

Explanation:

When transmitting data, a sequence number and/or time stamp built into the message to make it unique can be checked by the recipient to ensure that the message was not intercepted and replayed. This is known as replay protection, and could be used to verify that a payment instruction was not duplicated. Use of a cryptographic hashing algorithm against the entire message helps achieve data integrity. Enciphering the message digest using the senders private key, which signs the senders digital signature to the document, helps in authenticating the transaction. When the message is deciphered by the receiver using the senders public key, it ensures that the message could only have come from the sender. This process of sender authentication achieves nonrepudiation.