HFHE Challenge v2

Paused. This challenge is paused and remains unsolved. The repository is archived, and the challenge will be replaced by a new one.

This is the second version of the challenge. The first version was canceled because the public artifact included an unnecessary R_com commitment. That commitment allowed structured plaintext guesses to be checked offline, creating an unintended verification oracle. This issue has been removed in v2.

The task is to recover the plaintext from secret.ct. This file contains a private key and metadata associated with the address octC5eR9pLGKbpzTbDgHowkFt8HW7LZYb2gzehzxHamxuAZ.

No additional information is provided. If recovery is successful, the Octra web client can be used to access the wallet and claim the reward of 500,000 oct. The solver may also contact dev@octra.org to receive an additional 500,000 oct, for a total of 1,000,000 oct, or the equivalent amount in USDC.

The rest of the bounty package remains unchanged:

• manifest.json
• params.json
• pk.bin
• pvac_commit.txt
• secret.ct
• source/hfhe_bounty_artifact.cpp
• source/pvac_artifact_serialize.hpp

The ciphertext was generated using an updated version of pvac_hfhe_cpp, pinned to commit 071b0e9. It is recommended to use this specific version when reproducing the artifact format or testing attacks.

updated (july 11)

At the request of the majority, we are providing additional LPN artifacts associated with the live challenge ciphertext.

• lpn_samples

These samples expose the side target y = <A, S> xor e, with tau = 1/8 and n = 4096. Recovering S is an additional cryptanalysis target; the main bounty condition remains recovery of the plaintext/wallet payload from secret.ct.

A tool has also been added to validate the public metadata binding between the LPN artifacts and secret.ct.

• source/tools/verify_lpn_sample_binding.cpp