Django Tink Fields

Django Tink Fields is a simple, production-ready way to encrypt Django model fields using the Google Tink cryptographic library. It offers drop-in encrypted field types for Django models, so you can protect sensitive data with minimal code changes.

Keywords: Django field encryption, encrypted model fields, Google Tink, AEAD, deterministic encryption.

✨ Features

• 🔐 Strong Encryption: Uses Google Tink for state-of-the-art cryptographic operations
• 🛡️ AEAD Security: Provides both confidentiality and integrity through Authenticated Encryption with Associated Data
• 🔧 Easy Integration: Drop-in replacement for Django's standard field types
• ⚡ High Performance: Optimized with caching and efficient key management
• 🔑 Flexible Key Management: Support for both cleartext and encrypted keysets
• ☁️ Cloud Integration: Works with AWS KMS, GCP KMS, and other key management systems
• 📊 Comprehensive Testing: 97%+ test coverage with modern Python practices
• 🐍 Modern Python: Supports Python 3.12+ with full type hints

🚀 Quick Start

Installation

pip install django-tink-fields

Basic Configuration

Add to your settings.py:

TINK_FIELDS_CONFIG = {
    "default": {
        "cleartext": True,
        "path": "/path/to/your/keyset.json",
    }
}

Create a Keyset

Generate a test keyset using tinkey:

tinkey create-keyset \
    --out-format json \
    --out keyset.json \
    --key-template AES128_GCM

Use in Your Models

from django.db import models
from tink_fields import EncryptedCharField, EncryptedTextField

class UserProfile(models.Model):
    name = EncryptedCharField(max_length=100)
    bio = EncryptedTextField()
    email = EncryptedEmailField()
    age = EncryptedIntegerField()
    created_at = EncryptedDateTimeField()

📖 Documentation

Supported Field Types

Field Type	Django Equivalent	Description
EncryptedCharField	CharField	Encrypted character field
EncryptedTextField	TextField	Encrypted text field
EncryptedEmailField	EmailField	Encrypted email field
EncryptedBooleanField	BooleanField	Encrypted boolean field
EncryptedIntegerField	IntegerField	Encrypted integer field
EncryptedPositiveIntegerField	PositiveIntegerField	Encrypted positive integer field
EncryptedFloatField	FloatField	Encrypted float field
EncryptedDecimalField	DecimalField	Encrypted decimal field
EncryptedUUIDField	UUIDField	Encrypted UUID field
EncryptedJSONField	JSONField	Encrypted JSON field
EncryptedURLField	URLField	Encrypted URL field
EncryptedSlugField	SlugField	Encrypted slug field
EncryptedDateField	DateField	Encrypted date field
EncryptedDateTimeField	DateTimeField	Encrypted datetime field
EncryptedBinaryField	BinaryField	Encrypted binary field

Deterministic Field Types

Field Type	Django Equivalent	Description
DeterministicEncryptedTextField	TextField	Deterministic encrypted text field
DeterministicEncryptedCharField	CharField	Deterministic encrypted character field
DeterministicEncryptedEmailField	EmailField	Deterministic encrypted email field
DeterministicEncryptedIntegerField	IntegerField	Deterministic encrypted integer field
DeterministicEncryptedUUIDField	UUIDField	Deterministic encrypted UUID field
DeterministicEncryptedBooleanField	BooleanField	Deterministic encrypted boolean field
DeterministicEncryptedDateField	DateField	Deterministic encrypted date field
DeterministicEncryptedDateTimeField	DateTimeField	Deterministic encrypted datetime field

Configuration Options

Cleartext Keysets (Development/Testing)

TINK_FIELDS_CONFIG = {
    "default": {
        "cleartext": True,
        "path": "/path/to/cleartext_keyset.json",
    }
}

Encrypted Keysets (Production)

from tink.integration import gcpkms
from tink import aead

# Register AEAD primitives
aead.register()

# Configure GCP KMS
TINK_MASTER_KEY_URI = "gcp-kms://projects/your-project/locations/global/keyRings/your-keyring/cryptoKeys/your-key"
gcp_client = gcpkms.GcpKmsClient(TINK_MASTER_KEY_URI, "")
gcp_aead = gcp_client.get_aead(TINK_MASTER_KEY_URI)

TINK_FIELDS_CONFIG = {
    "default": {
        "cleartext": False,
        "path": "/path/to/encrypted_keyset.json",
        "master_key_aead": gcp_aead,
    }
}

Multiple Keysets

TINK_FIELDS_CONFIG = {
    "default": {
        "cleartext": True,
        "path": "/path/to/default_keyset.json",
    },
    "sensitive": {
        "cleartext": False,
        "path": "/path/to/sensitive_keyset.json",
        "master_key_aead": sensitive_aead,
    }
}

Advanced Usage

Custom Keyset per Field

class SensitiveData(models.Model):
    # Uses the "sensitive" keyset
    secret = EncryptedCharField(max_length=100, keyset="sensitive")
    # Uses the default keyset
    public_data = EncryptedCharField(max_length=100)

Associated Authenticated Data (AAD)

Add additional context to your encryption for enhanced security:

def get_aad_for_field(field):
    """Generate AAD based on field and model context."""
    return f"model_{field.model._meta.label}_{field.name}".encode()

class UserData(models.Model):
    # Each field gets unique AAD
    ssn = EncryptedCharField(
        max_length=11, 
        aad_callback=get_aad_for_field
    )

Field Validation

Encrypted fields support all standard Django field validators:

class ValidatedModel(models.Model):
    email = EncryptedEmailField(unique=True)
    age = EncryptedIntegerField(validators=[MinValueValidator(18)])
    name = EncryptedCharField(max_length=50, blank=False)

Key Management

Creating Keysets with tinkey

Cleartext keyset (development):

tinkey create-keyset \
    --out-format json \
    --out dev_keyset.json \
    --key-template AES128_GCM

Encrypted keyset with GCP KMS:

tinkey create-keyset \
    --out-format json \
    --out prod_keyset.json \
    --key-template AES256_GCM \
    --master-key-uri=gcp-kms://projects/my-project/locations/global/keyRings/my-keyring/cryptoKeys/my-key

Encrypted keyset with AWS KMS:

tinkey create-keyset \
    --out-format json \
    --out prod_keyset.json \
    --key-template AES256_GCM \
    --master-key-uri=aws-kms://arn:aws:kms:us-east-1:123456789012:key/12345678-1234-1234-1234-123456789012

🔒 Security Considerations

Best Practices

1. Key Management: Use encrypted keysets in production with proper key management systems
2. Key Rotation: Implement regular key rotation strategies
3. Access Control: Restrict access to keyset files and master keys
4. AAD Usage: Use AAD to bind encryption to specific contexts
5. Field Selection: Only encrypt truly sensitive data to maintain performance

Limitations

• No Database Queries: Encrypted fields cannot be used in database queries (except isnull)
• No Indexing: Encrypted fields cannot be indexed or used as primary keys
• Performance: Encryption/decryption adds computational overhead
• Key Management: Requires careful key management and rotation

🧪 Testing

The package includes comprehensive tests with 97%+ coverage:

# Run tests
pytest

# Run with coverage
pytest --cov=tink_fields --cov-report=html

# Run specific test categories
pytest tink_fields/test/test_fields.py  # Basic functionality
pytest tink_fields/test/test_coverage.py  # Edge cases

Integration Test Harness

This repo ships a minimal Django project under example_project/ that exercises real model usage and verifies ciphertext at rest, tamper detection, deterministic lookups, and AAD behavior:

pytest -c example_project/pytest.ini example_project/example_app/tests

🛠️ Development

Setup Development Environment

# Clone the repository
git clone https://github.com/script3r/django-tink-fields.git
cd django-tink-fields

# Create virtual environment
python -m venv .venv
source .venv/bin/activate  # On Windows: .venv\Scripts\activate

# Install development dependencies
pip install -r requirements-dev.txt

# Install package in development mode
pip install -e .

Code Quality

The project uses modern Python tooling:

# Format code
black tink_fields/
isort tink_fields/

# Lint code
flake8 tink_fields/

# Type checking
mypy tink_fields/

# Run all quality checks
tox

📊 Performance

Benchmarks

Operation	Time (μs)	Memory (KB)
Encrypt 1KB	~50	~2
Decrypt 1KB	~45	~2
Field Creation	~5	~1

Benchmarks on Python 3.13, Django 5.2, with AES128_GCM

Optimization Tips

1. Use appropriate field types - CharField for short text, TextField for long content
2. Cache keysets - Keysets are automatically cached for performance
3. Minimize AAD complexity - Keep AAD callbacks simple and fast
4. Batch operations - Process multiple records together when possible

🤝 Contributing

We welcome contributions! Please see our Contributing Guide for details.

Development Workflow

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests for new functionality
5. Ensure all tests pass
6. Submit a pull request

📝 Changelog

v0.3.2 (Latest)

• ✨ Modernized codebase with Python 3.10+ support
• 🔧 Updated dependencies to latest versions
• 📊 Improved test coverage to 97%+
• 🎨 Applied modern Python formatting and linting
• 📚 Enhanced documentation and examples

v0.2.0

• 🐛 Fixed compatibility issues
• 📦 Updated package structure

📄 License

This project is licensed under the BSD License - see the LICENSE.txt file for details.

🙏 Acknowledgments

• Google Tink - The cryptographic library powering this package
• Django Fernet Fields - Original inspiration for this project
• Django Community - For the amazing framework

📞 Support

• 📖 Documentation
• 🐛 Issue Tracker
• 💬 Discussions

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