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@victormeloasm victormeloasm released this 26 Aug 03:00
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HippoFrog v2.2 — Twist‑Safe ECDH + AES‑GCM (ECCFrog522PP)

Date: 2025-08-25

This is the first public release of HippoFrog built around the research-grade curve ECCFrog522PP (Presunto Power), featuring twist-safe ECDH, HKDF(SHA‑256), and AES‑256‑GCM with authenticated headers and ephemeral public keys.

Highlights

  • Custom curve: ECCFrog522PP (~522‑bit prime field, a = -9, cofactor h = 1, prime order n).
  • Key exchange: Ephemeral ECDH → HKDF‑SHA‑256 (salt=32B, info=param_hash || "HippoFrog v2.2 AES-256-GCM").
  • AEAD: AES‑256‑GCM (IV=12B, tag=16B) with AAD = Header + EphemeralPublicCompressed.
  • Public‑key hygiene: on‑curve check, subgroup check (n·Q=O), identity rejection.
  • Parameter binding: param_hash = SHA256(P|A|B|N|GX|GY), verified at decrypt.
  • Self‑describing file format: 86‑byte header + ephemeral (compressed) + ciphertext + tag.
  • CLI: --generate-keys, --validate-keys, --encrypt, --decrypt, --b (bench).
  • Docs: Deep README with full curve specification; SECURITY, CONTRIBUTING, Code of Conduct; CI workflow.

Changelog

Added

  • ECCFrog522PP curve parameters and deterministic parameter hash binding.
  • Ephemeral ECDH + HKDF(SHA‑256) → 32‑byte AES key.
  • AES‑256‑GCM with 12‑byte IV and 16‑byte tag; AAD covers header + ephemeral public key.
  • Header (86B): magic="HFv1", version=1, param_hash(32), salt(32), iv(12), eph_len(2).
  • Key validation: on‑curve, subgroup (n·Q=O), identity rejection.
  • CLI commands: --generate-keys, --validate-keys, --encrypt, --decrypt, --b.
  • GitHub Actions workflow for build + smoke tests.
  • Comprehensive README including Full Specification of ECCFrog522PP (Presunto Power).

Changed

  • Curve construction: fixed BIGNUM handling (use BN_dec2bn/BN_set_word on BIGNUM*; pass actual pointers to EC_GROUP_new_curve_GFp).
  • Negative a handling: set a = -9 using BN_set_word(abs(a)) + BN_set_negative(…,1) to avoid modular misinterpretation.
  • Makefile: enforces -std=c++20, links -lssl -lcrypto, and silences OpenSSL 3.x deprecation warnings for legacy EC calls.

Fixed

  • Key generation failure caused by incorrect handling of negative a (now correctly represented as negative BIGNUM).
  • Compile‑time errors from passing int returns of BN_* into APIs expecting BIGNUM*.
  • Assorted minor robustness improvements in EC parameter initialization and memory hygiene.

Security

  • Twist/invalid‑curve protections: on‑curve test; subgroup check (n·Q=O) with cofactor h=1; identity rejection.
  • AAD coverage for header + ephemeral public; param hash mismatch aborts decryption.
  • Explicit disclaimer: custom curve; research/experimental only; no public cryptanalysis claimed.

Documentation

  • README now documents end‑to‑end flow, file format, AAD, parameter binding, and full ECCFrog522PP spec.
  • Added SECURITY.md, CONTRIBUTING.md, CODE_OF_CONDUCT.md, issue templates.

CI

  • Ubuntu build with libssl-dev, runs: keygen → validate → encrypt/decrypt round‑trip.

Known Issues

  • eph_len in the header uses host endianness (typically little‑endian on x86_64). Producers and consumers must be consistent; a later version may switch to network byte order.
  • Uses OpenSSL EC legacy APIs (3.x deprecation warnings are suppressed). A future provider‑based refactor is planned.
  • No chunked streaming for very large files (encrypts the whole buffer in memory).
  • Private keys are stored as unencrypted PEM; handle with care (file permissions, backups).

Upgrade Notes

  • If you were on a pre‑release or local fork, rebuild with the updated Makefile and regenerate keys to ensure the fixed curve initialization (negative a) is in effect.

Assets

Suggested release assets:

  • HippoFrog-v2.2-linux-x86_64.zip (binary + README.md)
  • Source code (zip) / Source code (tar.gz) (GitHub autogenerated)
  • SHA256SUMS (checksums for all assets)

You can compute checksums with:

sha256sum HippoFrog-v2.2-linux-x86_64.zip > SHA256SUMS

Verification / Smoke Test

./bin/HippoFrog --generate-keys
./bin/HippoFrog --validate-keys
echo "ok" > t.txt
./bin/HippoFrog --encrypt t.txt
./bin/HippoFrog --decrypt t.txt.hf
diff -q t.txt t.txt.dec && echo OK

Thanks

Thanks to early testers and reviewers who kicked the tires on keygen and the decrypt path.

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