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 sender’s private key, which signs the sender’s digital signature to the document, helps in
authenticating the transaction. When the message is deciphered by the receiver using the sender’s public key,
it ensures that the message could only have come from the sender. This process of sender authentication
achieves nonrepudiation.