Create BAP Identity

Create and manage BAP (Bitcoin Attestation Protocol) identities.

Installation

bun add bsv-bap @bsv/sdk

Creating an Identity

import { BAP } from "bsv-bap";
import { PrivateKey } from "@bsv/sdk";

// Create BAP instance with new key
const privateKey = PrivateKey.fromRandom();
const bap = new BAP({ rootPk: privateKey.toWif() });

// Create identity
const identity = bap.newId("Alice Smith");

console.log("Identity Key:", identity.getIdentityKey());
console.log("Root Address:", identity.rootAddress);
console.log("Signing Address:", identity.getCurrentAddress());

BAP ID Format

The BAP library calls this the identityKey (via getIdentityKey()), but to avoid confusion with BRC-31 "identity keys" (which are public keys), we call it the BAP ID everywhere else.

Derivation: base58(ripemd160(sha256(rootAddress))) where rootAddress is the Bitcoin address of the member key.

This is NOT a Bitcoin address, NOT a public key, and NOT a BRC-31 identity key. It is a stable hash identifier that persists across signing key rotations.

BAP ID vs BRC-31 Identity Key

| | BAP ID | BRC-31 Identity Key | |---|---|---| | What | Stable identity hash | Compressed secp256k1 public key | | Format | ~27 char base58 string | 66 hex chars (02/03 prefix) | | Example | Go8vCHAa4S6AhXK... | 02a08a4bbb07ead... | | Used in | BAP attestations, ClawNet bapId, Sigma Auth bap_id | BRC-31 Authrite headers, BRC-42/43 key derivation | | Derived from | Member key's address (rootAddress) | Direct from private key |

In BRC-100 wallets, the member key's pubkey is the BRC-31 identity key. You can derive the BAP ID from it: pubkey.toAddress() = rootAddress, then hash. This only works for the member key — NOT signing keys.

Key Derivation

BAP uses Type42 (BRC-42) key derivation with BRC-43 invoice numbers:

| Purpose | Invoice Number | Security Level | |---------|---------------|----------------| | Signing key | 1-bapid-identity | 1 (public protocol) | | Friend encryption | 2-friend-{sha256(friendBapId)} | 2 (user-approved) |

Signing Messages

import { Utils } from "@bsv/sdk";
const { toArray } = Utils;

// Sign a message
const message = toArray("Hello World", "utf8");
const { address, signature } = identity.signMessage(message);

// Verify (on any BAP instance)
const isValid = bap.verifySignature("Hello World", address, signature);

Friend Encryption

Derive friend-specific encryption keys for private communication:

// Get encryption pubkey for a friend (share in friend requests)
const friendPubKey = identity.getEncryptionPublicKeyWithSeed(friendBapId);

// Encrypt data for friend
const ciphertext = identity.encryptWithSeed("secret message", friendBapId);

// Decrypt data from friend
const plaintext = identity.decryptWithSeed(ciphertext, friendBapId);

Export/Import

// Export for backup
const backup = bap.exportForBackup("My Identity");
// { ids: "...", createdAt: "...", rootPk: "..." }

// Import from backup
const bap2 = new BAP({ rootPk: backup.rootPk });
bap2.importIds(backup.ids);

CLI Option

For quick operations, the bsv-bap package includes a CLI:

npm install -g bsv-bap

bap create --name "Alice"     # Create identity (~/.bap/identity.json)
bap sign "Hello World"        # Sign message
bap verify "msg" "sig" "addr" # Verify signature
bap info                      # Show identity info
bap friend-pubkey <bapId>     # Get friend encryption pubkey
bap encrypt <data> <bapId>    # Encrypt for friend
bap decrypt <text> <bapId>    # Decrypt from friend
bap export                    # Export backup JSON
bap import <file>             # Import from backup

Key Rotation & Path Management

BAP separates stable identity from active signing key:

• rootPath (e.g., bap:0) — derives the stable member key. Never changes. This is the key used for identity linkage and member backup export.
• currentPath (e.g., bap:0:1) — derives the active wallet/signing key. Rotates with incrementPath().
• Identity key persists across all rotations — it's derived from the rootAddress, not the signing address.

// Key rotation
const identity = bap.newId("Alice");
console.log(identity.currentPath); // "bap:0" (initially same as rootPath)

identity.incrementPath();
console.log(identity.currentPath); // "bap:0:1" (rotated)
// identity.identityKey is unchanged!

Identity Destruction

To permanently destroy an identity (emergency kill switch if signing key is compromised), broadcast an ID transaction with address 0, signed by the rootAddress:

BAP_PREFIX | ID | identityKey | 0 | AIP_SIGNATURE(rootAddress)

MemberID Counter-Based Rotation

MemberID uses a counter for signing key derivation:

memberKey → deriveChild(pubkey, "bap:{counter}") → currentKey
currentKey → deriveChild(pubkey, "1-sigma-identity") → signingKey

The protocol name sigma-identity is 5 characters to meet BRC-100 derivation requirements. Calling member.rotate() increments the counter, producing a new signing key while the member key stays fixed.

Stable vs Active Keys

| Key | Derivation | Changes? | Use | |-----|-----------|----------|-----| | Member key | rootPath derived from master | Never | Identity linkage, auth tokens, backup export | | Signing key | currentPath derived from member + counter | On rotation | On-chain attestations, AIP signatures |

import { getStableMemberPubkey, getActiveWalletPubkey } from "./bap/utils";

const stablePubkey = getStableMemberPubkey(identity); // Fixed
const activePubkey = getActiveWalletPubkey(identity);  // Rotates

Identity Actions via @1sat/actions (Recommended)

For BRC-100 wallet operations, use the identity actions from @1sat/actions. These use the wallet's BAP signing key ([1, "bapid"] / "identity") via AIP.

Seeding the wallet: When Sigma Identity publishes a BAP ID, it seeds the wallet via one of two paths:

• Wallet-funded: Root key signs the ID OP_RETURN via PrivateKeySigner + AIP.sign(), then publishIdentity.execute() funds via the BRC-100 wallet. Output auto-lands in the bap basket.
• Droplit-funded (onboarding): Droplit funds the broadcast, then wallet.internalizeAction() seeds the bap basket with type:id, bapId:<hash> tags.

Publish Identity (wallet-funded)

import { publishIdentity, createContext } from '@1sat/actions'
import { AIP, PrivateKeySigner } from '@bopen-io/templates'
import { OP, Script, Utils } from '@bsv/sdk'

// Sigma Identity builds and signs the BAP ID OP_RETURN with the root key
const script = new Script()
script.writeOpCode(OP.OP_FALSE)
script.writeOpCode(OP.OP_RETURN)
script.writeBin(Utils.toArray('1BAPSuaPnfGnSBM3GLV9yhxUdYe4vGbdMT'))
script.writeBin(Utils.toArray('ID'))
script.writeBin(Utils.toArray(bapId))
script.writeBin(Utils.toArray(currentAddress))
// ... append AIP signature via PrivateKeySigner(rootKey) ...

const ctx = createContext(wallet)
const result = await publishIdentity.execute(ctx, {
  signedScript: signedScript.toHex(),
})
// result: { txid, rawtx, error }
// Action parses the script to extract bapId, verifies AIP signature,
// and confirms currentAddress matches this wallet's BAP derivation.
// Output lands in bap basket with type:id tag.

Update Profile

import { updateProfile, createContext } from '@1sat/actions'

const ctx = createContext(wallet)

const result = await updateProfile.execute(ctx, {
  profile: {
    '@context': 'https://schema.org',
    '@type': 'Person',
    name: 'Alice Smith',
    description: 'BSV developer',
  },
})
// result: { txid, rawtx, error }
// Publishes BAP ALIAS on-chain, relinquishes any previous alias outputs

Get Profile

import { getProfile, createContext } from '@1sat/actions'

const result = await getProfile.execute(createContext(wallet), {})
// result: { bapId, profile, error }
// Parses current ALIAS from wallet's bap basket
// Deduplicates if multiple alias outputs exist

Attest

import { attest, createContext } from '@1sat/actions'

const result = await attest.execute(createContext(wallet), {
  attestationHash: 'sha256-of-urn:bap:id:attribute:value:nonce',
  counter: '0',
})
// result: { txid, rawtx, error }
// Publishes BAP ATTEST on-chain signed with BAP identity

Resolve BAP ID

import { resolveBapId, createContext } from '@1sat/actions'

const bapId = await resolveBapId(createContext(wallet))
// Returns the BAP ID string from the wallet's bap basket, or null

Identity Architecture

Sigma Identity (root key domain)
  └─ BAP Master Key (xprv)
      └─ Identity N
          ├─ Root key (member key) → BAP ID = base58(ripemd160(sha256(rootAddress)))
          └─ Active key → BRC-100 wallet root key
              └─ BAP signing key (Type42: "1-bapid-identity")

• Sigma Identity handles: key generation, identity creation, ID record publication (root key), key rotation, OAuth
• @1sat/actions handles: publishIdentity (pre-signed script), attest, updateProfile, getProfile (signing key only)
• BAP ID is stable across key rotations — it's the identity anchor
• AIP signature proves who authorized each transaction

Using bsv-bap Library Directly

For operations outside the BRC-100 wallet (raw WIF usage, CLI scripts).

Installation

bun add bsv-bap @bsv/sdk

Creating an Identity

import { BAP } from "bsv-bap";
import { PrivateKey } from "@bsv/sdk";

const privateKey = PrivateKey.fromRandom();
const bap = new BAP({ rootPk: privateKey.toWif() });
const identity = bap.newId("Alice Smith");

console.log("BAP ID:", identity.getIdentityKey());
console.log("Root Address:", identity.rootAddress);
console.log("Signing Address:", identity.getCurrentAddress());

Key Derivation

BAP uses Type42 (BRC-42) key derivation with BRC-43 invoice numbers:

| Purpose | Invoice Number | Security Level | |---------|---------------|----------------| | Signing key | 1-bapid-identity | 1 (public protocol) | | Friend encryption | 2-friend-{sha256(friendBapId)} | 2 (user-approved) |

Related Skills

• key-derivation - Type42 and BRC-43 key derivation patterns
• message-signing - BSM, BRC-77, AIP, and Sigma signing protocols
• encrypt-decrypt-backup - bitcoin-backup CLI for .bep encrypted backups