Paper 2023/441

Unconditionally secure ciphers with a short key for a source with unknown statistics

Boris Ryabko, Federal Research Center for Information and Computational Technologies

We consider the problem of constructing an unconditionally secure cipher with a short key for the case where the probability distribution of encrypted messages is unknown. Note that unconditional security means that an adversary with no computational constraints can obtain only a negligible amount of information ("leakage") about an encrypted message (without knowing the key). Here we consider the case of a priori (partially) unknown message source statistics. More specifically, the message source probability distribution belongs to a given family of distributions. We propose an unconditionally secure cipher for this case. As an example, one can consider constructing a single cipher for texts written in any of the languages of the European Union. That is, the message to be encrypted could be written in any of these languages.

Available format(s)
Secret-key cryptography
Publication info
unconditionally secure cipherentropically-secure symmetric encryptionindistinguishabilityuniversal code
Contact author(s)
boris @ ryabko net
2023-03-27: approved
2023-03-26: received
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      author = {Boris Ryabko},
      title = {Unconditionally secure ciphers with a short key for a source with unknown statistics},
      howpublished = {Cryptology ePrint Archive, Paper 2023/441},
      year = {2023},
      note = {\url{}},
      url = {}
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