Ether-Link

A lightweight Rust library focused on enabling secure communication between Ethereum address owners. Ether-Link provides simple yet powerful tools for Ethereum key management, message signing, signature verification, and end-to-end encryption - allowing Ethereum wallet owners to securely exchange both authenticated and encrypted messages. Using EIP-5630 compliant ECIES encryption, address owners can communicate privately by encrypting messages that only specific Ethereum addresses can decrypt, while maintaining message authenticity through cryptographic signatures.

Core Focus

Ether-Link is specifically designed to facilitate:

• Secure Communication between Ethereum address owners
• Identity Verification using cryptographic signatures
• Message Authentication ensuring only valid Ethereum address owners can participate
• Decentralized Trust leveraging Ethereum's cryptographic primitives

Features

• Key Management: Generate new Ethereum key pairs with compressed and uncompressed public keys
• Address Derivation: Deterministically generate Ethereum addresses from public keys
• Message Signing: Sign messages using Ethereum's standard signing format
• Signature Verification: Verify message signatures against Ethereum addresses
• Timestamped Messages: Automatic timestamp inclusion to prevent replay attacks
• Message Encryption: End-to-end encryption for messages between Ethereum addresses
  • EIP-5630 compliant ECIES (Elliptic Curve Integrated Encryption Scheme) implementation
  • Encrypt messages that only specific Ethereum addresses can decrypt
  • AES-256-GCM encryption with HKDF key derivation
• Message Decryption: Decrypt messages encrypted with ECIES for your Ethereum address
• Custom Key Import: Create wallets from existing private keys

Upcoming Features (Next Version)

• Batch Operations: Ability to sign or verify multiple messages efficiently
• Extended Compatibility: Support for additional Ethereum signature standards and wallets
• More Cipher Options: Support for additional encryption algorithms and modes

Installation

Add this to your Cargo.toml:

[dependencies]
ether-link = "0.1.0"

Usage Examples

Secure Communication Flow

Ether-Link enables a simple communication pattern between Ethereum address owners:

1. Sender signs a message with their Ethereum private key
2. Recipient verifies the signature using the sender's Ethereum address
3. Communication is authenticated without requiring password exchange or central authorities

Generating a New Key Pair

use ether_link::Wallet;

fn main() {
    // Generate a fresh Ethereum key pair
    let wallet = Wallet::new();
    
    println!("Private Key: {}", wallet.privkey);
    println!("Ethereum Address: {}", wallet.address);
    println!("Compressed Public Key: {}", wallet.pubkey_compressed);
    println!("Uncompressed Public Key: {}", wallet.pubkey_uncompressed);
}

Creating a Wallet from Existing Private Key

use ether_link::Wallet;

fn main() {
    // Create a wallet using an existing private key
    // warning: Do not send anything to the wallet below.
    let private_key = "0x7a28b5ba57c53603b0b07b56bba752f7784bf506fa95edc395f5cf6c7514fe9d";
    let wallet = Wallet::from_private_key(Some(private_key));
    
    println!("Ethereum Address: {}", wallet.address);
    // Should print: 0x008aeeda4d805471df9b2a5b0f38a0c3bcba786b
}

Signing a Message

use ether_link::Wallet;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let wallet = Wallet::new();
    let message = "Hello, Ethereum!";
    
    let signature_json = wallet.sign_message(message).await?;
    println!("Signature: {}", signature_json);
    
    Ok(())
}

Encrypting a Message

use ether_link::Wallet;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let wallet = Wallet::new();
    let message = "Secret message for recipient!";
    let recipient_pubkey = "0x027a4066efb9f66a65cf5f30c5ccdc7c0cdd9608f699eb3c5da2172ea2f6f579dc"; // Recipient's compressed public key
    
    let encrypted = wallet.encrypt_message(message, recipient_pubkey)?;
    println!("Encrypted: {}", encrypted);
    
    Ok(())
}

Decrypting a Message

use ether_link::Wallet;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let wallet = Wallet::new(); // The recipient's wallet
    let encrypted_message = "0x0123..."; // Encrypted message from sender
    
    let decrypted = wallet.decrypt_message(encrypted_message)?;
    println!("Decrypted message: {}", decrypted);
    
    Ok(())
}

Verifying a Signature

use ether_link::EthereumSignature;
use serde_json::Value;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Assume signature_json is the output from sign_message
    let signature_json: Value = serde_json::from_str(&signature_json_str)?;
    
    let address = signature_json["address"].as_str().unwrap();
    let signed_message = signature_json["signed_message"].as_str().unwrap();
    let signature = signature_json["signature"].as_str().unwrap();
    
    let eth_signature = EthereumSignature::new(
        address.to_string(),
        signed_message.to_string(),
        signature.to_string()
    );
    
    let is_valid = eth_signature.verify()?;
    println!("Signature is valid: {}", is_valid);
    
    Ok(())
}

Key Components

• Wallet: Core structure for generating and managing Ethereum key pairs
• new(): Create a new random wallet
• from_private_key(): Create a wallet from an existing private key
• sign_message(): Async method to sign messages with timestamps for security
• encrypt_message(): Method to encrypt messages using EIP-5630 compliant ECIES (Elliptic Curve Integrated Encryption Scheme) with AES-256-GCM encryption and HKDF key derivation for a specific recipient's public key
• decrypt_message(): Method to decrypt ECIES encrypted messages (EIP-5630) using AES-256-GCM decryption with HKDF key derivation for messages encrypted for this wallet
• EthereumSignature: Structure to verify signed messages against Ethereum addresses

Applications

• Decentralized Identity: Authenticate users by their Ethereum addresses
• Secure Messaging: Build messaging systems where sender identity is cryptographically verified
• dApp Authentication: Implement authentication flows without passwords
• Smart Contract Interaction: Sign messages intended for on-chain verification
• Wallet-to-Wallet Communication: Enable direct secure messaging between wallet owners
• Private Data Exchange: Exchange encrypted data that only specific Ethereum addresses can access

Security Notes

• Private keys are stored in memory as hex strings. Handle with appropriate security measures
• The library adds timestamps to signed messages by default to prevent replay attacks
• Always verify signatures against known addresses before trusting signed messages
• Encrypted messages follow the EIP-5630 standard for ECIES encryption
• The same shared secret is derived by both sender and recipient for encryption/decryption

License

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

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the project
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request