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Perfectly Secret Encryption

links: Modern Cryptography MOC - Index

Perfect secrecy

For a scheme to be perfectly secret, observing this ciphertext should have no effect on the adversary's knowledge regarding the actual message that was sent.

The ciphertext reveals nothing about the underlying plaintext

Perfect indistinguishability

An encryption scheme is perfectly indistinguishable if no adversary can succeed with probability better than \(1/2\) (in the indistinguishability experiment)

Definitions

  • An Encryption scheme is formally defined with \(\Pi = (Gen, Enc, Dec)\)
  • Encryption algorithm is probabilistic (encryption might output a different ciphertext when run multiple times): \(c \leftarrow Enc_k(m)\)
  • Decryption algorithm is deterministic: \(m := Dec_k(c)\)

links: Modern Cryptography MOC - Index