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wtf is hfhe-challenge?

octra-labs/hfhe-challenge — explained in plain English

Analysis updated 2026-05-18

29C++Audience · researcherComplexity · 5/5Setup · hard

TL;DR

A cryptography bounty challenge where solving a cryptanalysis puzzle to recover a hidden plaintext can unlock a reward paid in the project's OCT token.

Mindmap

mindmap
  root((HFHE Challenge))
    What it does
      Cryptography bounty puzzle
      Recover hidden plaintext
      Reward in OCT token
    Tech stack
      C++
      pvac_hfhe_cpp
      LPN samples
    Use cases
      Cryptanalysis research
      Verifying artifact binding
      Studying LPN targets
    Audience
      Cryptography researchers
      Bounty hunters

Code map

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filefunction / class

Why would anyone build with this?

REASON 1

Attempt to cryptanalyze the provided ciphertext and artifact files to recover a hidden wallet key.

REASON 2

Study the provided LPN samples as a separate cryptanalysis target related to the main challenge.

REASON 3

Use the included verification tool to confirm the binding between the LPN artifacts and secret.ct.

What's in the stack?

C++Cryptography

How it stacks up

octra-labs/hfhe-challengealex-shayo/bakkes-mod-installlocalai-org/moss-transcribe.cpp
Stars292929
LanguageC++C++C++
Setup difficultyhardeasymoderate
Complexity5/52/54/5
Audienceresearchergeneraldeveloper

Figures from each repo's GitHub metadata at analysis time.

How do you spin it up?

Difficulty · hard Time to first run · 1day+

This is a cryptanalysis puzzle, not installable software, and requires cryptography expertise to attempt.

The README does not state a software license for this repository.

Wtf does this do

This repository hosts a cryptography bounty challenge rather than a piece of software meant to be installed or run for everyday use. It is the second version of a puzzle where the goal is to recover a plaintext value hidden inside a file called secret.ct, which contains a private key and metadata tied to a specific cryptocurrency wallet address. The first version of this challenge was canceled because its public files included an extra commitment value that accidentally let solvers check structured guesses offline, which is considered an unfair shortcut. That flaw has been removed in this second version. No hints beyond the provided files are given. If someone successfully recovers the plaintext, they can use it with the Octra web client to access the wallet and claim a reward of 500,000 OCT, the project's token. Contacting the project's email address afterward can unlock an additional 500,000 OCT, bringing the total possible reward to 1,000,000 OCT or an equivalent amount in USDC. The bounty package bundles several files: a manifest, parameter file, public key, a commitment text file, the ciphertext itself, and C++ source files used to generate and serialize the challenge artifact. The ciphertext was produced using a specific pinned commit of a separate tool called pvac_hfhe_cpp, and the README recommends using that exact version when trying to reproduce the artifact format or attempt an attack. An update posted July 11 added extra cryptanalysis material called LPN samples, which expose a secondary mathematical target related to a value called S, separate from the main goal of recovering the wallet's plaintext. A verification tool was also added so solvers can confirm that the LPN samples are properly linked to the original secret.ct file. The README does not state a software license for this repository.

Yoink these prompts

Prompt 1
Explain what an LPN sample is and how it relates to the cryptanalysis target in this challenge.
Prompt 2
Walk me through the files included in this bounty package and what each one is for.
Prompt 3
What was the flaw in version one of this challenge that let solvers check guesses offline?
Prompt 4
Help me understand how the verify_lpn_sample_binding tool checks artifact consistency.

Frequently asked questions

wtf is hfhe-challenge?

A cryptography bounty challenge where solving a cryptanalysis puzzle to recover a hidden plaintext can unlock a reward paid in the project's OCT token.

What language is hfhe-challenge written in?

Mainly C++. The stack also includes C++, Cryptography.

What license does hfhe-challenge use?

The README does not state a software license for this repository.

How hard is hfhe-challenge to set up?

Setup difficulty is rated hard, with roughly 1day+ to a first successful run.

Who is hfhe-challenge for?

Mainly researcher.

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