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This skill should be used when the user asks to "sign a message", "verify a signature", "use BSM", "use BRC-77", "implement Sigma signing", "create signed messages", "authenticate with Bitcoin", or mentions message signing, signature verification, or authentication protocols on BSV.
npx skill4agent add b-open-io/bsv-skills message-signing| Approach | Package | Use Case |
|---|---|---|
| Direct SDK | | Simple message signing (BSM, BRC-77) |
| Templates | | Script parsing/creation for protocols |
| Sigma Protocol | | Transaction-bound signatures |
import { BSM, PrivateKey, Signature, BigNumber } from "@bsv/sdk";
const privateKey = PrivateKey.fromWif("L1...");
const message = [/* byte array */];
// Sign
const signature = BSM.sign(message, privateKey, "raw") as Signature;
const h = new BigNumber(BSM.magicHash(message));
const recovery = signature.CalculateRecoveryFactor(privateKey.toPublicKey(), h);
const compactSig = signature.toCompact(recovery, true, "base64");
// Verify - recover public key and check address
const sig = Signature.fromCompact(compactSig, "base64");
for (let r = 0; r < 4; r++) {
try {
const pubKey = sig.RecoverPublicKey(r, new BigNumber(BSM.magicHash(message)));
if (BSM.verify(message, sig, pubKey)) {
console.log("Signer:", pubKey.toAddress());
break;
}
} catch { /* try next */ }
}import { SignedMessage, PrivateKey, PublicKey } from "@bsv/sdk";
const signer = PrivateKey.fromWif("L1...");
const message = [/* byte array */];
// Public signature (anyone can verify)
const sig = SignedMessage.sign(message, signer);
const valid = SignedMessage.verify(message, sig);
// Private signature (only recipient can verify)
const recipientPubKey = PublicKey.fromString("02...");
const privateSig = SignedMessage.sign(message, signer, recipientPubKey);
const recipientKey = PrivateKey.fromWif("K1...");
const privateValid = SignedMessage.verify(message, privateSig, recipientKey);examples/bsm-sign-verify.tsexamples/brc77-private-sig.ts@bopen-io/templatesimport { Sigma, SigmaAlgorithm, BitCom } from "@bopen-io/templates";
import { PrivateKey, Hash } from "@bsv/sdk";
// Decode from existing script
const bitcom = BitCom.decode(script);
const sigmas = Sigma.decode(bitcom);
// Create signature (given pre-computed hashes)
const inputHash = Array.from(Hash.sha256(outpointBytes));
const dataHash = Array.from(Hash.sha256(scriptDataBytes));
const sigma = Sigma.sign(inputHash, dataHash, privateKey, {
algorithm: SigmaAlgorithm.BRC77, // or SigmaAlgorithm.BSM
vin: 0
});
// Verify
const valid = sigma.verifyWithHashes(inputHash, dataHash);
// Generate locking script
const lockingScript = sigma.lock();import { AIP, BitCom } from "@bopen-io/templates";
// Decode AIP from script
const bitcom = BitCom.decode(script);
const aips = AIP.decode(bitcom);
// Create AIP signature
const aip = await AIP.sign(dataBytes, privateKey, {
algorithm: "BITCOIN_ECDSA",
fieldIndexes: [0, 1, 2] // optional: specific fields to sign
});
const valid = aip.verify();examples/sigma-template.tssigma-protocolbun add sigma-protocolimport { Sigma, Algorithm } from "sigma-protocol";
import { Transaction, PrivateKey } from "@bsv/sdk";
// Create Sigma instance
const sigma = new Sigma(tx, targetVout, sigmaInstance, refVin);
// Sign with BSM (default)
const { signedTx } = sigma.sign(privateKey);
// Sign with BRC-77
const { signedTx: tx2 } = sigma.sign(privateKey, Algorithm.BRC77);
// Sign with BRC-77 for specific verifier (private)
const { signedTx: tx3 } = sigma.sign(privateKey, Algorithm.BRC77, verifierPubKey);
// Verify
const valid = sigma.verify();
const privateValid = sigma.verify(recipientPrivateKey); // for private BRC-77// First signature (user with BSM)
const sigma1 = new Sigma(tx, 0, 0);
const { signedTx } = sigma1.sign(userKey, Algorithm.BSM);
// Second signature (platform with BRC-77)
const sigma2 = new Sigma(signedTx, 0, 1);
sigma2.sign(platformKey, Algorithm.BRC77);
// Verify each
sigma2.setSigmaInstance(0);
sigma2.verify(); // User
sigma2.setSigmaInstance(1);
sigma2.verify(); // Platformexamples/sigma-multi-sig.ts| Feature | BSM | BRC-77 |
|---|---|---|
| Key derivation | Direct | Child key per message |
| Recovery | From signature | Embedded in signature |
| Private verify | No | Yes (with recipient key) |
| SDK module | | |
| Scenario | Approach |
|---|---|
| Simple message auth | Direct SDK (BSM or BRC-77) |
| BAP identity signing | |
| Parse existing Sigma/AIP scripts | Templates |
| Build BitCom transaction outputs | Templates |
| Sign transaction OP_RETURN data | sigma-protocol |
| Multiple signatures per output | sigma-protocol |
| Platform + user dual signing | sigma-protocol |
bsv-bapimport { BAP } from "bsv-bap";
import { Utils } from "@bsv/sdk";
const { toArray } = Utils;
const bap = new BAP({ rootPk: wif });
const identity = bap.getId(bap.listIds()[0]);
// Sign with BSM (uses derived identity signing key)
const message = toArray("Hello World", "utf8");
const { address, signature } = identity.signMessage(message);
// Verify BSM signature
const isValid = bap.verifySignature("Hello World", address, signature);npm install -g bsv-bapcreate-bap-identityreferences/brc-77-spec.mdreferences/sigma-advanced.mdexamples/bsm-sign-verify.tsexamples/brc77-private-sig.tsexamples/sigma-template.tsexamples/sigma-multi-sig.ts