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Secure Multi-Token Transaction Management Using Bitcoin.js
As a Bitcoin.js developer, you’ve probably come across the need to manage multi-signature transactions. A multi-signature (multiSig) wallet allows multiple addresses to authorize and confirm transactions on behalf of a single address. In this article, we’ll explore how to create a secure and reliable multiSig setup in Bitcoin.js.
Problem: OP_CHECKSIGADD
If you use the OP_CHECKSIGADD option, the signature of one or more signatures will be appended to another public key. However, if there is only one valid signature, the network will likely reject the transaction. To mitigate this risk, we’ll take a different approach by using “OP_CHECKSIG” and “OP_EQUAL” with a threshold of 3–2.
Creating a Secure MultiSig Configuration
To create a multiSig configuration in Bitcoin.js, you need to follow these steps:
- Create a 3-2 limit account: Define the public key that will be used for the primary account. This key must have at least three signatures, and at least two of them must be valid.
- Create a secondary account: Create another public key that will be used to authorize transactions on behalf of the primary account. This key must have less than 4 signatures (a single signature is not valid).
- Generate a shared secret: Use the OP_CHECKSIG option to generate a shared secret between two accounts. This shared secret will contain all the information needed for authorization.
- Verify the shared secret: Use the OP_EQUAL option with the shared secret and one of the secondary account signatures to verify its validity.
Sample Code
const Bitcoinjs = require('bitcoinjs-lib');
// Create a 3-2 limit account
const primaryAccountPubkey = 'xprv...';
const primarySigPubkey1 = 'xprv...'; // 3 signatures
const primarySigPubkey2 = 'xprv...'; // 2 signatures
const primarySigPubkey3 = 'xprv...'; // invalid signature
// Create a secondary account
const SecondaryAccountPubkey = 'xprv...';
const SecondarySigPubkey1 = 'xprv...'; // less than 4 signatures (one is invalid)
// Generate a shared secret using OP_CHECKSIG and one of the primary account signatures
async function generateSharedSecret() {
const sharedSecretPubkey = await Bitcoinjs.Secp256k1.createKeyPair(primaryAccountPubkey);
const signature1 = await Bitcoinjs.Secp256k1.sign(sharedSecretPubkey, primarySigPubkey1);
const signature2 = await Bitcoinjs.Secp256k1.sign(sharedSecretPubkey, primarySigPubkey2);
const signature3 = await Bitcoinjs.Secp256k1.sign(sharedSecretPubkey, primarySigPubkey3);
return { sharedSecret: JSON.stringify({ secret: sharedSecretPubkey, signatures: [signature1, signature2, signature3] }) };
}
// Verify the shared secret using OP_EQUAL with one of the secondary account signatures
async function verifySharedSecret(sharedSecret) {
const { sharedSecret: { secret, signatures} } = JSON.parse(sharedSecret);
const signature = await Bitcoinjs.Secp256k1.sign(secret, SecondarySigPubkey1);
return signature === signatures[0];
}
// Example usage:
generateSharedSecret().then(SharedSecret => {
verifySharedSecret(sharedSecret).then(verified => console.log(verified));
});
Best Practices
- Use a secure and trusted seed for your primary account.
- Ensure that all secondary accounts have less than 4 signatures (one is invalid).
- Keep the shared secret secure to prevent unauthorized access.
- Consider using a stronger cryptographic library such as “Bitcoinjs-secp256k1” which offers better security features.
By following these steps and best practices, you can securely manage multi-Sig transactions in your Bitcoin.js application. Remember to always handle sensitive information with care and follow the guidelines provided by the Bitcoin community.