ChaCha20 💃

Overview

This repository hosts an implementation of the ChaCha20 stream cipher, Poly1305 message authentication code, and ChaCha20-Poly1305 Authenticated Encryption with Associated Data (AEAD) construction as per RFC 8439. These cryptographic algorithms offer robust solutions for ensuring data confidentiality, integrity, and authenticity.

ChaCha20

ChaCha20 is a modern stream cipher known for its speed and security. It is designed to provide strong encryption and has become a popular choice in various cryptographic protocols, such as TLS and secure messaging applications.

Key Features:

• High Speed: Excels in software implementations, especially on platforms without specialized hardware support for cryptography.
• Security: Designed to be secure against a wide range of cryptographic attacks.
• Flexibility: Easily adaptable for both large data encryption and real-time data streaming.

Best Practices:

• Ensure unique nonces for each encryption operation.
• Securely manage and store encryption keys.

Poly1305

Poly1305 is a fast and secure message authentication code (MAC) that works in conjunction with a cipher like ChaCha20. It provides a strong level of assurance against message tampering.

Key Features:

• Efficiency: Exceptionally fast, making it suitable for high-throughput applications.
• Security: Offers strong guarantees of authenticity.
• One-Time Key Usage: Each key must only be used once to maintain security.

Best Practices:

• Never reuse a key; always generate a new key for each message.
• Combine with a secure cipher like ChaCha20 for complete data protection.

ChaCha20-Poly1305 AEAD

ChaCha20-Poly1305 AEAD combines the strengths of ChaCha20 and Poly1305, encrypting and authenticating data in a single step. It's recommended for scenarios where both confidentiality and integrity are crucial.

Key Features:

• Authenticated Encryption: Simultaneously encrypts and authenticates data.
• Nonce-Misuse Resistance: Provides security even if nonces are reused (though nonce reuse is not recommended).
• Efficient: Leverages the performance benefits of ChaCha20 and Poly1305.

Best Practices:

• Avoid nonce reuse to ensure the highest level of security.
• Verify the authenticity of decrypted data before using it.

Background and History

ChaCha20

Developed by Daniel J. Bernstein, ChaCha20 is an evolution of the earlier Salsa20 cipher. It was designed to provide strong cryptographic security while being highly efficient in software implementations.

Poly1305

Also developed by Daniel J. Bernstein, Poly1305 provides a way to authenticate messages securely and is often used in combination with ciphers like ChaCha20.

RFC 8439

RFC 8439 standardizes the algorithms and provides comprehensive guidelines for their implementation and use, ensuring consistency and security across different applications.

Benchmarks

Performance

Benchmarks were conducted on a MacBook Pro with the following specifications:

• Chip: Apple M2 Max
• Memory: 32GB

The benchmarks were performed by processing 1,000,000 bytes in each of 10 runs for each operation. The runtimes and throughput are as follows:

Operation	Runtime (µs)	Throughput (MB/s)
chacha20-poly1305	5884.89	169.93
chacha20	4206.36	237.74
poly1305	1405.16	711.66

These results highlight the high efficiency of the algorithms, making them ideal for high-throughput applications.

Usage Examples

Real-World Use Case: Secure Data Encryption/Decryption

Scenario: Encrypting and decrypting sensitive data using ChaCha20.

import 'dart:typed_data';
import 'package:chacha/export.dart';

Uint8List encrypt({
  required Uint8List plaintext,
  required Uint8List key,
  required Uint8List nonce,
}) {
  final ChaCha20 chacha20 = ChaCha20(key, nonce);
  return chacha20.convert(plaintext);
}

Uint8List decrypt({
  required Uint8List ciphertext,
  required Uint8List key,
  required Uint8List nonce,
}) {
  final ChaCha20 chacha20 = ChaCha20(key, nonce);
  return chacha20.convert(ciphertext);
}

Real-World Use Case: Secure Data Encryption/Decryption Stream

Scenario: Encrypting and decrypting sensitive data using ChaCha20 streaming.

import 'dart:typed_data';
import 'package:chacha/export.dart';

Stream<List<int>> encrypt({
  required Stream<Uint8List> plaintext,
  required Uint8List key,
  required Uint8List nonce,
}) {
  final ChaCha20 chacha20 = ChaCha20(key, nonce);
  return plaintext.transform(chacha20);
}

Stream<List<int>> decrypt({
  required Stream<Uint8List> ciphertext,
  required Uint8List key,
  required Uint8List nonce,
}) {
  final ChaCha20 chacha20 = ChaCha20(key, nonce);
  return ciphertext.transform(chacha20);
}

Real-World Use Case: Secure File Encryption/Decryption Stream

Scenario: Encrypting and decrypting sensitive files using ChaCha20 streaming.

import 'dart:typed_data';
import 'package:chacha/export.dart';

void process({
  required File inputFile,
  required File outputFile,
  required Uint8List key,
  required Uint8List nonce,
}) {
  final ChaCha20 chacha20 = ChaCha20(key, nonce);
  inputFile.openRead().transform(chacha20).pipe(outputFile.openWrite());
}

Real-World Use Case: Data Authentication

Scenario: Generating a MAC for a message using Poly1305.

import 'dart:typed_data';
import 'package:chacha/poly1305.dart';

Uint8List authenticateMessage(Uint8List message, Uint8List key) {
  Poly1305 poly1305 = Poly1305(key)
  Uint8List tag = poly1305.convert(message);
  // Use the tag for message verification
}

Real-World Use Case: Secure Communication

Scenario: Encrypting and authenticating a message using ChaCha20-Poly1305 AEAD.

import 'dart:typed_data';
import 'package:chacha/chacha20_poly1305.dart';

Uint8List secureCommunication(Uint8List message, Uint8List key, Uint8List nonce) {
  Uint8List encryptedMessage = ChaCha20Poly1305(null, key, nonce, true).convert(message);
  // Send encryptedMessage securely
}

Contribution

Contributions to improve the implementation, enhance security, and extend functionality are welcome. If you find any issues or have suggestions, please feel free to open an issue or submit a pull request.