Hash Functions, Message Digests, Digital Signatures

• Problem: The private-key based “signature” is too slow to generate & is a lot of overhead

• Solution:

  • 1. Convert the message into a smaller-sized, tough-to-guess numeric value using a “one-way hash function” (eg: MD5, SHA)
  • 2. This numeric value (16-32 bytes) is called a “message digest” or a Message Authentication Code (MAC)
  • 3. Encrypt the MAC with the private key to create a “digital signature”
  • 4. Receiver generates MAC, decrypts digital signature and compares to authenticate

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