Definitions Edit

A message digest (also known as a hash value) is

[a] hash that uniquely identifies data. Changing a single bit in the data stream used to generate the message digest will yield a completely different message digest.[1]
[a] digital signature that uniquely identifies data and has the property that changing a single bit in the data will cause a completely different message digest to be generated.[2]
[a] cryptographic checksum, typically generated for a file that can be used to detect changes to the file.[3]

A message digest is "[t]he result of applying a cryptographic hash function to a message."[4]

Overview Edit

"A message digest can be used to provide integrity. It can be used to determine if a file or message has been changed and can also help to identify duplicate files.

"If a sender sends a message and its message digest to a recipient, the recipient can recompute the message digest to protect against accidental changes in the data. However, this does not protect the recipient from an attacker, who can intercept the original message and replace it with a new message and the message digest of that new message."[5]

References Edit

  1. NIST Special Publication 800-86, at C-2.
  2. NIST Special Publication 800-92.
  3. CNSSI 4009.
  4. NIST Special Publication 800-107.
  5. NIST Special Publication 800-32.
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