Hope4Sec has developed innovative expertise in cryptographic security evaluation in the field of symmetric cryptology (stream ciphers, block ciphers, hybrid ciphers). In contrast to statistical or algebraic approaches, we have developed combinatorial techniques that are better adapted to the natural complexity of cryptographic algorithms.
The principle is to rewrite an encryption system (stream or block cipher) into a combinatorially equivalent system, and to translate the problem of the secret key recovery into a known combinatorial problem, the practical complexity of which is significantly lower (time and data) than the exhaustive search on the one hand, and known attacks on the other (statistical and algebraic attacks). This approach is called Equivalent Combinatorial Rewriting (ECR). This approach applies to both known-plaintext and ciphertext-only cryptanalysis.
Our expertise is intended exclusively for the cryptology evaluation of algorithms, to the exclusion of any cryptanalysis activity or service.
As a first concrete example of this approach, we have designed the Cipherbent6 concept cipher and obtained a cryptanalysis that is better than all known attacks.
Cipherbent6 source code is available here. The white paper presenting our first results is available here
We have successfully extended the Equivalent Combinatorial Approach to the Achterbahn stream cipher. The white paper is available here
As the ECR techniques are non-public, the proof of our results can be provided on request via a challenge approach (sending a cipher sequence and returning the secret key) when
applicable or after an appropriate cooperation agreement.
We only accept requests from companies or government institutions (see our Contact page).