Strong secrecy

Strong secrecy is a term used in formal proof-based cryptography for making propositions about the security of cryptographic protocols. It is a stronger notion of security than syntactic (or weak) secrecy. Strong secrecy is related with the concept of semantic security or indistinguishability used in the computational proof-based approach. Bruno Blanchet provides the following definition for strong secrecy:

Strong secrecy means that an adversary cannot see any difference when the value of the secret changes[1]

For example, if a process encrypts a message m an attacker can differentiate between different messages, since their ciphertexts will be different. Thus m is not a strong secret. If however, probabilistic encryption were used, m would be a strong secret. The randomness incorporated into the encryption algorithm will yield different ciphertexts for the same value of m.

See also

Notes

  1. Blanchet, B. (2004) Automatic proof of strong secrecy for security protocols. In proceedings of the IEEE Symposium on Security and Privacy, pp 86-100. http://www.di.ens.fr/~blanchet/publications/BlanchetOakland04.html


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