Diffie-Hellman Key Agreement

• Diffie-Hellman key exchange is a protocol that allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure communications channel.
  • This key can then be used to encrypt subsequent communications using a symmetric key.

• It should be difficult for the sender to solve the recipient's private key and for the recipient to solve the sender's private key.
  • If it is easy for the sender to solve for recipient's private key (or vice versa), then an eavesdropper may:
    • Substitute its own private / public key pair,
    • Plug recipient's public key into its private key,
    • Produce a fake shared secret key,
    • Solve the recipient's private key,
    • Use that to solve for the shared secret key.
  • An eavesdropper may attempt to choose a public / private key pair that is easy for it to solve for recipient's private key.

How is Diffie-Hellman implemented?

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© 2006 John Michael Pierobon

Notes