I have read the paper by Anderson and Biham [0] describing the ciphers Bear and Lion, which combine a PRG and a hash function (each cipher does that in a different way). the authors proved that a key recovery attack on the ciphers would imply breaking the PRG and hash function used. I also read the paper by Morin [1] in which he shows a man-in-the-middle attack on Bear and Lion, and also proposes a new cipher (Aardvark) of the same kind, immune to such attack.

Was there any attack on Aardvark?

And are there other block ciphers with proof of security?

The references are the following (sorry, I couldn't find exactly the publication years and conference names)

[0] Ross Anderson and Eli Biham. Two Practical and Provably Secure Block Ciphers: BEAR and LION.

[1] Pat Morin (1996). Provably Secure and Efficient Block Ciphers.

  • 1
    $\begingroup$ Wrong link for Morin's paper. $\endgroup$ Commented Mar 4, 2011 at 9:20

1 Answer 1


Construction of provably-secure block ciphers are considered in the following papers:

The construct by Pat Morin and many others are reviewed in Building Secure Block Ciphers on Generic Attacks Assumptions.

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    $\begingroup$ A paper by Dodis & Puniya proves more properties of the Luby-Rackoff (Feistel) construction, like security even if some of the internal states are leaked. $\endgroup$
    – mikero
    Commented Mar 5, 2011 at 3:11
  • $\begingroup$ The paper "Building Secure Block Ciphers on Generic Attacks Assumptions" is interesting, but it doesn't actually review Morin's paper -- it only mentions it (en passant, without much discussion). But it helped a lot already! Thank you! $\endgroup$
    – Jay
    Commented Mar 17, 2011 at 20:53

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