Message Digest

• A message digest is a statistically unique hash, or message authentication code, of a file.
  • It is typically 128 bits long.

• A message authentication code takes a message and a secret key and generates a "MAC tag".
  • It is difficult for an attacker to generate a valid (message, tag) pair that matches the original one.

• MD5 is an algorithm intended for digital signature applications where a large file must be compressed in a secure manner before being encrypted with a private key under an encryption method.
  • md5sum is a program that can be used to generate a hash.
  • If a Web site is secure, then a file that matches its hash can be considered valid.

What is a digital certificate?

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© 2006 John Michael Pierobon

Notes