Changes in v0.60

This release includes significant updates to dependencies, Python compatibility improvements, and new cryptographic schemes.

Warning

This release contains breaking changes. Please review the migration guide below before upgrading.

Breaking Changes and Migration Guide

This section documents changes that may require modifications to existing code when upgrading from v0.50 to v0.60.

Python Version Requirements

Python 2.x and Python 3.5-3.7 are no longer supported.

Aspect

Old (v0.50)

New (v0.60)

Minimum Python

2.7 / 3.x

3.8+

Tested versions

2.7, 3.5-3.9

3.8, 3.9, 3.10, 3.11, 3.12

Migration: Upgrade to Python 3.8 or later before installing v0.60.

Package Name Change

The PyPI package name has been updated to follow Python packaging conventions:

Aspect

Old (v0.50)

New (v0.60)

Package name

Charm-Crypto

charm-crypto

Import name

charm

charm (unchanged)

Migration: Update pip commands and requirements files:

# Old
pip install Charm-Crypto

# New
pip install charm-crypto

The import name remains charm, so existing Python code continues to work without changes.

Dependency Version Changes

Dependency

Old (v0.50)

New (v0.60)

Impact

PBC Library

0.5.14

1.0.0

Low (API compatible)

pyparsing

>=2.1.5,<2.4.1

>=2.1.5,<4.0

Low (more permissive)

OpenSSL

1.0.x / 1.1.x

3.x

Medium

OpenSSL Migration: Ensure OpenSSL 3.x is installed:

  • macOS: brew install openssl@3

  • Ubuntu/Debian: apt install libssl-dev

  • Fedora/RHEL: dnf install openssl-devel

Removed Features

  1. Python 2.x support removed - All Python 2 compatibility code has been removed from C extension modules.

  2. UninstallCommand removed - The custom python setup.py uninstall command has been removed due to use of deprecated platform.linux_distribution().

    Migration: Use standard pip uninstall:

    pip uninstall charm-crypto

  3. distribute_setup.py removed - The legacy setuptools bootstrap script has been removed.

    Migration: Use modern pip/setuptools:

    pip install --upgrade pip setuptools wheel
pip install charm-crypto

CTR Counter Module Change

The low-level _counter module now returns bytes instead of str from counter operations.

Impact: Medium - Only affects code that directly uses the _counter module.

Migration: If you use the _counter module directly, ensure your code handles bytes objects:

# The counter now returns bytes
counter_value = counter()  # Returns bytes, not str

Most users access CTR mode through SymmetricCryptoAbstraction which handles this internally.

Internal Implementation Changes (Non-Breaking)

The following changes are internal and should not affect user code:

  • Hash functions now use OpenSSL EVP API instead of deprecated low-level functions

  • Windows PRNG seeding uses RAND_poll() instead of deprecated RAND_screen()

  • Integer module uses PyLong_* functions (Python 3 native) instead of PyInt_*

Migration Checklist

Before upgrading from v0.50 to v0.60:

  1. ☐ Verify Python version is 3.8+: python --version

  2. ☐ Verify OpenSSL version is 3.x: openssl version

  3. ☐ Update package name in requirements: Charm-Crypto → charm-crypto

  4. ☐ Remove any python setup.py uninstall usage (use pip uninstall)

  5. ☐ Check for direct _counter module usage (ensure code handles bytes)

  6. ☐ Rebuild from source if using custom builds

Dependency Updates

  • PBC Library upgraded from 0.5.14 to 1.0.0 - The Pairing-Based Cryptography library has been updated to its latest release (June 2025). This is a drop-in replacement with no API changes, maintaining full backward compatibility with existing pairing-based schemes.

  • Updated documentation and build scripts to reflect PBC 1.0.0 URLs and paths

  • Updated CI/CD pipeline for PBC 1.0.0 builds

  • pyparsing constraint relaxed - Now allows pyparsing 2.x and 3.x (>=2.1.5,<4.0)

  • OpenSSL 3.x support - Full compatibility with OpenSSL 3.x across all C extension modules

Python Compatibility

  • Python 3.8+ required - Minimum Python version is now 3.8

  • Python 3.12+ support - Fixed PyLongObject internal structure changes in Python 3.12+ (Issues #326, #313)

  • Added PY_SSIZE_T_CLEAN macro definition for Python 3.10+ compatibility

  • Fixed Py_SET_SIZE behavior changes in Python 3.12+

  • Optimized longObjToMPZ by removing temporary variables

  • Fixed PyLong_SHIFT definition for Windows 64-bit builds

  • Added support for Python 3.11 and 3.12 in testing

  • Modernized CTR counter module to use Python 3 Bytes API

New Schemes

  • CP-ABE with Privacy Protection and Accountability - Implemented CP hiding ABE scheme from “Attribute Based Encryption with Privacy Protection and Accountability for CloudIoT”

  • User Collusion Avoidance CP-ABE - Implemented scheme with efficient attribute revocation for cloud storage

  • PS Signature Schemes - Added Pointcheval-Sanders signature implementations

  • Certificateless Public Key Cryptography - Added CLPKC scheme

  • Lamport OTS - Implemented Lamport One-Time Signature scheme

Numeric Attribute Comparisons

This release introduces support for numeric attribute comparisons in CP-ABE policies, implementing the “bag of bits” technique from the Bethencourt-Sahai-Waters (BSW07) paper.

Features:

  • Support for numeric comparisons in policies: >=, >, <=, <, ==

  • Automatic conversion of numeric comparisons to bit-level attribute expressions

  • NumericAttributeHelper class for easy policy expansion and attribute generation

  • Negation support via equivalent expression conversion

Example Usage:

from charm.toolbox.ABEnumeric import NumericAttributeHelper

# Create helper with 8-bit integers (values 0-255)
helper = NumericAttributeHelper(num_bits=8)

# Expand policy with numeric comparisons
policy = helper.expand_policy("age >= 21 and level > 5")

# Generate user attributes for key generation
user_attrs = helper.user_attributes({'age': 25, 'level': 7, 'role': 'admin'})

Negation Limitation:

The underlying Monotone Span Program (MSP) does not support logical negation. Use the negate_comparison() function to convert negated comparisons to equivalent positive forms:

  • NOT (age >= 21) → age < 21

  • NOT (age == 21) → (age < 21) or (age > 21)

See ABEnumeric - Numeric Attribute Encoding for complete documentation.

ZKP Compiler (v0.60-0.70)

This release introduces a new secure Zero-Knowledge Proof (ZKP) compiler module that provides a type-safe, formally verified approach to constructing ZKP protocols.

New Proof Types:

  • Schnorr Proofs - Standard discrete log proofs with Fiat-Shamir transform

  • DLEQ Proofs - Discrete Log Equality proofs for proving equality of discrete logs

  • Representation Proofs - Proofs of knowledge of a representation in multiple bases

  • AND Composition - Combine multiple proofs with logical AND

  • OR Composition - Combine multiple proofs with logical OR (witness-indistinguishable)

  • Range Proofs - Efficient proofs that a committed value lies within a range

Key Features:

  • Batch Verification - Verify multiple proofs efficiently with significant performance gains

  • BN254 Curve Support - 128-bit security level with optimized pairing operations

  • Type-Safe API - Compile-time verification of proof structure

  • Fiat-Shamir Heuristic - Automatic conversion from interactive to non-interactive proofs

Deprecation Notice:

The legacy zkp_generator module is deprecated and will be removed in v0.80. Migrate to the new zkp_compiler module for improved security and performance.

Performance Benchmarks:

Operation

Single Proof

Batch (100 proofs)

Schnorr Prove

0.8ms

45ms

Schnorr Verify

1.2ms

35ms (batch)

DLEQ Prove

1.5ms

85ms

DLEQ Verify

2.1ms

60ms (batch)

Range Proof (64-bit)

15ms

800ms

See toolbox/zkp_compiler for complete documentation.

Build System

  • Modern Python packaging - Added pyproject.toml following PEP 517/518 standards

  • Added GitHub Actions CI/CD workflow replacing Travis CI

  • Updated configure.sh to support ARM64/AARCH64 architectures (Apple Silicon, etc.)

  • Updated configure.sh to detect Python 3.8-3.12

  • Fixed multiple definition errors in benchmark module

  • Improved Relic library integration

  • Added type stubs (.pyi files) for C extension modules

Bug Fixes

  • Fixed segmentation faults in EC and pairing modules (PY_SSIZE_T_CLEAN)

  • Fixed downcaseTokens function missing from policytree.py

  • Fixed coeff key handling in recoverCoefficients method

  • Fixed integer hashing issues

  • Improved EC bignum conversion

  • Use math.gcd instead of deprecated fractions.gcd

  • Support all-AND policy expressions for testing ABE schemes

  • Fixed AEC.c cipher mode issues with Python 3.10+

  • Removed deprecated platform.linux_distribution() usage

Documentation

  • Updated README with comprehensive Linux/Unix build instructions

  • Added platform-specific installation guides for Ubuntu/Debian, Fedora/RHEL/CentOS, Arch Linux

  • Updated links to point to jhuisi.github.io

  • Added macOS tutorial for Apple Silicon

Contributors

Thanks to all contributors for this release, including bug fixes, new schemes, and compatibility improvements.