Add nodePublicAccountID

packages/ripple-keypairs/README.md

@@ -40,6 +40,13 @@ eddsa deterministic signatures.
   publicKey: 'n9MU2RsULUayZnWeLssjbMzVRPeVUUMgiPYTwe8eMgpdGDWp5t8C' }
 ```
 
+## Derive accountID matching a validator public key (aka public generator)
+```js
+> var nodePublicAccountID = require('ripple-keypairs').nodePublicAccountID;
+> nodePublicAccountID('n9MXXueo837zYH36DvMc13BwHcqtfAWNJY5czWVbp7uYTj7x17TH')
+'rhcfR9Cg98qCxHpCcPBmMonbDBXo84wyTn'
+```
+
 ## Sign a transaction
 see [examples/sign-transaction.js](examples/sign-transaction.js)
 ```js

packages/ripple-keypairs/src/ed25519.js

@@ -63,4 +63,6 @@ Ed25519Pair.prototype.verify = function(message, signature) {
   return this.key().verify(message, signature);
 };
 
-module.exports = Ed25519Pair;
+module.exports = {
+  Ed25519Pair
+};

packages/ripple-keypairs/src/index.js

@@ -6,8 +6,8 @@ const rand = require('brorand');
 
 const {seedFromPhrase, createAccountID} = require('./utils');
 const {KeyPair, KeyType} = require('./keypair');
-const Ed25519Pair = require('./ed25519');
-const K256Pair = require('./secp256k1');
+const {Ed25519Pair} = require('./ed25519');
+const {K256Pair, accountPublicFromGenerator} = require('./secp256k1');
 
 KeyPair.fromSeed = function(seedBytes, type, options) {
   assert(type === 'secp256k1' || type === 'ed25519');
@@ -54,6 +54,12 @@ function generateValidatorKeys(opts={}) {
   return deriveValidator(randGen(16));
 }
 
+function nodePublicAccountID(publicKey) {
+  const genBytes = codec.decodeNodePublic(publicKey);
+  const accountPublicBytes = accountPublicFromGenerator(genBytes);
+  return codec.encodeAccountID(createAccountID(accountPublicBytes));
+}
+
 function validatorKeysFromSeed(seed) {
   const {type, bytes} = codec.decodeSeed(seed);
   assert(type === KeyType.secp256k1);
@@ -71,5 +77,6 @@ module.exports = {
   generateWallet,
   generateValidatorKeys,
   walletFromSeed,
-  validatorKeysFromSeed
+  validatorKeysFromSeed,
+  nodePublicAccountID
 };

packages/ripple-keypairs/src/secp256k1.js

@@ -57,6 +57,14 @@ function deriveSecret(seed, opts={}) {
             .add(privateGen).mod(order);
 }
 
+function accountPublicFromGenerator(publicGenBytes) {
+  const rootPubPoint = secp256k1.curve.decodePoint(publicGenBytes);
+  const scalar = deriveScalar(publicGenBytes, 0);
+  const point = secp256k1.g.mul(scalar);
+  const offset = rootPubPoint.add(point);
+  return offset.encodeCompressed();
+}
+
 /*
 * @class
 */
@@ -116,4 +124,7 @@ K256Pair.prototype.verify = function(message, signature) {
   }
 };
 
-module.exports = K256Pair;
+module.exports = {
+  K256Pair,
+  accountPublicFromGenerator
+};

packages/ripple-keypairs/test/keypairs-test.js

@@ -14,7 +14,8 @@ const {
   generateWallet,
   walletFromSeed,
   generateValidatorKeys,
-  validatorKeysFromSeed
+  validatorKeysFromSeed,
+  nodePublicAccountID
 } = keypairs;
 
 const {SerializedObject} = require('ripple-lib');
@@ -155,6 +156,13 @@ describe('generateValidatorKeys', function() {
     assert.deepEqual(actual, expected);
     assert.deepEqual(validatorKeysFromSeed(actual.seed), expected);
   });
+
+  it('can generate the correct accountID from validator public key', () => {
+    const accountID = 'rhcfR9Cg98qCxHpCcPBmMonbDBXo84wyTn';
+    const validatorPublic =
+          'n9MXXueo837zYH36DvMc13BwHcqtfAWNJY5czWVbp7uYTj7x17TH';
+    assert.equal(nodePublicAccountID(validatorPublic), accountID);
+  });
 });
 
 describe('K256Pair', function() {