Digital Signature

• A digital signature is an encrypted message digest.

• A message digest is created by:
  • Taking a message and using a hashing algorithm to compute a string typically 128 bits long.
    • This string is called a message digest.
    • MD5 is a common hashing algorithm.
  • The message digest is encrypted with the sender's private key.
    • The encrypted message digest is known as a digital signature.

• A digital signature servers three important purposes:
  • Verifies data integrity.
  • Provies authentication of the sender.
  • Accountability
    • The loss of the private key means that all digitally signed communications can still be repudiated.
    • Attaching a digital signature prevents repudiation.

Is a message digest the same as a message authentication code?

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© 2006 John Michael Pierobon

Notes