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Strong secrecy is a term used in cryptography. Bruno Blanchet provides the following definition:

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.


  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.