Cryptanalysis Challenge: Recover the Secret Vector from a Hybrid Collatz–SHA-512–ML-KEM-768 Seed Generator

Open cryptanalysis challenge for a hybrid seed-generation scheme that uses the Collatz orbit as a deterministic expander, a 20-bit one-time-pad mask, a derangement, SHA-512, and ML-KEM-768 (FIPS 203). The full mechanism, reference code, and a target SHA-512 hash are provided. The goal is to invite the community to analyze the design, find weaknesses, or confirm its resistance under standard assumptions. Collatz is used here as a deterministic expander, not as a cryptographic primitive. The security relies on the CSPRNG, the OTP mask, SHA-512, and ML-KEM-768. What counts as a break: (1) recover the secret vector V'' such that SHA-512(prefix || serialize(V'')) equals the target hash; (2) recover N0 and the corresponding k_i, masks, and permutation; (3) demonstrate a statistically significant bias in V'' that reduces its entropy below 280 bits; (4) find a side channel or implementation flaw that leaks V'' or N0 in a realistic threat model. Status: Open challenge. Unaudited design. Do not use for real data. Deadline: 6 months from publication (24 April 2027).