From fc77e559202d0f10807f78c95efd1a43f2c3e7d9 Mon Sep 17 00:00:00 2001
From: Tyera Eulberg <tyera@solana.com>
Date: Fri, 20 Dec 2019 16:14:37 -0700
Subject: [PATCH] fix: add PublicKey createWithSeed method

---
 web3.js/src/publickey.js       | 10 +++++++++
 web3.js/test/publickey.test.js | 40 ++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/web3.js/src/publickey.js b/web3.js/src/publickey.js
index c2fc63b434..3976661442 100644
--- a/web3.js/src/publickey.js
+++ b/web3.js/src/publickey.js
@@ -2,6 +2,7 @@
 
 import BN from 'bn.js';
 import bs58 from 'bs58';
+import hasha from 'hasha';
 
 /**
  * A public key
@@ -75,4 +76,13 @@ export class PublicKey {
   toString(): string {
     return this.toBase58();
   }
+
+  /**
+   * Derive a public key from another key, a seed, and a programId.
+   */
+  static createWithSeed(fromPublicKey: PublicKey, seed: string, programId: PublicKey): PublicKey {
+    const buffer = Buffer.concat([fromPublicKey.toBuffer(), Buffer.from(seed), programId.toBuffer()])
+    const hash = hasha(buffer, {algorithm: 'sha256'});
+    return new PublicKey('0x' + hash);
+  }
 }
diff --git a/web3.js/test/publickey.test.js b/web3.js/test/publickey.test.js
index d861573a5e..4cdc38ef30 100644
--- a/web3.js/test/publickey.test.js
+++ b/web3.js/test/publickey.test.js
@@ -223,3 +223,43 @@ test('equals (II)', () => {
 
   expect(key1.equals(key2)).toBe(true);
 });
+
+test('createWithSeed', () => {
+  const defaultPublicKey = new PublicKey([
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+  ]);
+  const derivedKey = PublicKey.createWithSeed(defaultPublicKey, 'limber chicken: 4/45', defaultPublicKey);
+
+  expect(derivedKey.equals(new PublicKey('9h1HyLCW5dZnBVap8C5egQ9Z6pHyjsh5MNy83iPqqRuq'))).toBe(true);
+});