Secure Anonymous Complaint Submission Protocol

Project Overview

This project implements a hybrid cryptographic protocol combining Zero-Knowledge Proofs and Blind Signatures to enable secure, anonymous complaint submission with the following properties:

• Anonymity: No party can link a complaint to a specific user
• Authentication: Only authorized users can submit complaints
• One-per-user: Each user can submit exactly one complaint per round
• Verifiability: Anyone can verify all valid complaints were included

Protocol Approach

Hybrid: ZK-Proofs + Blind Signatures

This approach combines:

• Blind Signatures: For anonymous credential issuance during registration
• Zero-Knowledge Proofs: For efficient membership proofs and nullifier verification
• Merkle Trees: For efficient authorization set representation
• Nullifiers: For preventing double submissions

Project Structure

.
├── README.md
├── design_document.md          # Comprehensive protocol design document
├── implementation/             # Protocol implementation code
│   ├── setup.py               # Setup phase implementation
│   ├── registration.py        # Registration phase
│   ├── submission.py          # Submission phase
│   ├── verification.py        # Verification phase
│   └── merkle_tree.py         # Merkle tree utilities
├── diagrams/                   # Protocol flow diagrams
│   ├── protocol_flow.png
│   └── security_model.png
├── presentation/               # Presentation materials
│   ├── slides.md
│   └── presentation_notes.md
├── security_analysis/          # Security analysis documents
│   ├── threat_model.md
│   └── security_proofs.md
└── final_report.md            # Final project report

Getting Started

Prerequisites

• Python 3.8 or higher
• pip (Python package manager)

Installation

1. Clone or navigate to the project directory:

cd project5-secure-anonymous-complaint-submission-protocol

2. Install required dependencies:

pip install -r requirements.txt

This will install:

• pycryptodome - Cryptographic primitives
• pytest - Testing framework
• Other required dependencies

How to Run

Quick Start: Run Complete Protocol Demo

Run the complete protocol flow (all phases):

python implementation/test_protocol.py

This demonstrates:

• ✅ Setup: Authority generates keys and builds Merkle tree
• ✅ Registration: User registers and obtains credential
• ✅ Submission: User submits complaint anonymously
• ✅ Verification: Public verification of submission
• ✅ Duplicate Prevention: Second submission rejected

Expected Output:

============================================================
Secure Anonymous Complaint Submission Protocol - Test
============================================================

[1] SETUP PHASE
------------------------------------------------------------
✓ Generated RSA keys (2048 bits)
✓ Added 3 authorized users
✓ Built Merkle tree (root: ...)
✓ Public parameters generated

[2] REGISTRATION PHASE
------------------------------------------------------------
✓ User 'student1' registered successfully
  Credential signature: ...
  Note: User secret is NOT known to authority

[3] SUBMISSION PHASE
------------------------------------------------------------
✓ Complaint submitted successfully
  Complaint: This is a test complaint about academic misconduct.
  Nullifier: ...
  Round ID: round_2024_01
  Note: Authority cannot link nullifier to user (doesn't know secret)

[4] VERIFICATION PHASE
------------------------------------------------------------
Verification Results:
  Proof valid: True
  Nullifier unique: True
  Complaint valid: True
  Overall valid: True
✓ Submission verified successfully

[5] BULLETIN BOARD
------------------------------------------------------------
✓ Submission added to bulletin board
  Total submissions: 1
  Unique nullifiers: 1

[6] DUPLICATE PREVENTION TEST
------------------------------------------------------------
✓ Duplicate submission correctly rejected

============================================================
ALL TESTS PASSED!
============================================================

Run Unit Tests

Run all unit tests to verify requirements:

# Run all tests
pytest tests/

# Run with verbose output
pytest tests/ -v

# Run specific test file
pytest tests/test_requirements.py -v

# Run with coverage report
pytest tests/ --cov=implementation --cov-report=html

Run Individual Phase Examples

Test each phase separately:

# Setup phase
python -c "from implementation.setup import example_setup; example_setup()"

# Registration phase
python -c "from implementation.registration import example_registration; example_registration()"

# Submission phase
python -c "from implementation.submission import example_submission; example_submission()"

# Verification phase
python -c "from implementation.verification import example_verification; example_verification()"

Protocol Phases

1. Setup Phase: Authority generates keys and builds Merkle tree
2. Registration Phase: Users obtain anonymous credentials
3. Submission Phase: Users submit complaints with ZK-proofs
4. Verification Phase: Public verification of submissions

Using the Protocol in Your Code

See USAGE.md for detailed code examples showing how to use each phase of the protocol programmatically.

Testing Requirements

The test suite verifies all security requirements:

• ✅ Anonymity: Authority cannot link submissions to users
• ✅ Authentication: Only authorized users can submit
• ✅ One-per-user: Each user submits at most one per round
• ✅ Verifiability: Public verification works correctly

Run tests:

pytest tests/test_requirements.py -v

Documentation

• Design Document: design_document.md - Complete protocol specification
• Security Analysis: security_analysis/ - Threat model and security proofs
• Final Report: final_report.md - Project summary and analysis
• Presentation: presentation/ - Slides and presentation notes
• Usage Guide: USAGE.md - Detailed code examples

Troubleshooting

Import Errors

If you get import errors, make sure you're running from the project root:

cd /path/to/project5-secure-anonymous-complaint-submission-protocol
python implementation/test_protocol.py

Missing Dependencies

If dependencies are missing:

pip install -r requirements.txt

RSA Key Generation is Slow

For faster testing, use smaller keys (not recommended for production):

authority = AuthoritySetup(key_size=1024)  # Smaller for testing

Note: Use 2048+ bits for production!

Python Version Issues

Make sure you're using Python 3.8 or higher:

python --version  # Should show 3.8+

If you have multiple Python versions, use:

python3 implementation/test_protocol.py

Project Structure

.
├── README.md                    # This file
├── requirements.txt             # Python dependencies
├── design_document.md          # Complete protocol design
├── final_report.md             # Final project report
├── USAGE.md                    # Detailed usage guide
├── implementation/             # Protocol implementation
│   ├── setup.py               # Setup phase
│   ├── registration.py        # Registration phase
│   ├── submission.py          # Submission phase
│   ├── verification.py        # Verification phase
│   ├── merkle_tree.py         # Merkle tree utilities
│   └── test_protocol.py       # Complete protocol test
├── tests/                      # Unit tests
│   ├── test_setup.py
│   ├── test_registration.py
│   ├── test_submission.py
│   ├── test_verification.py
│   ├── test_requirements.py  # Requirements verification
│   └── test_completeness.py
├── security_analysis/          # Security documentation
│   ├── threat_model.md
│   └── security_proofs.md
├── presentation/               # Presentation materials
│   ├── slides.md
│   └── presentation_notes.md
└── diagrams/                   # Protocol diagrams
    ├── protocol_flow.txt
    └── security_model.txt

License

Academic project for WPI CS 525/625 - Cryptography.