Which of the following is NOT a property of a message digest?

The rationale behind the correct response lies in the fundamental characteristics of a message digest. A message digest is a fixed-size string of characters derived from an input message of arbitrary length, typically using cryptographic hash functions. One of the key properties of message digests is that they are designed to be one-way functions, which means that it is computationally infeasible to revert the process and recreate the original message from the digest. This ensures the integrity and authenticity of the data without exposing the original content.

In contrast, the characteristics of message digests include the requirement that no two distinct messages should produce the same digest. This unique mapping helps in verifying that even the slightest change in the input produces a completely different digest, enhancing security. Additionally, it should not be easy to find a different input that results in the same digest (a property known as collision resistance), which is crucial for maintaining the integrity of the hashing process across various applications.

Moreover, using the entire contents of the original message means that the digest is sensitive to any alterations. Therefore, it ensures that even minor changes in the original data lead to significantly different digests, preserving the integrity of the data during verification processes. This property aligns well with the overall objective of message digests in digital signatures