From ecbf109a716639a36415ab23b8edc2df36ad4070 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Wed, 23 Mar 2016 00:39:20 +0000
Subject: [PATCH] Support instantation with public keys

---
 README.md     |  3 ++-
 index.js      | 33 ++++++++++++++++++++++++++++-----
 test/index.js | 21 +++++++++++++++++++++
 3 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index 64974cc..c107e39 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,8 @@ Features not supported:
 Constructors:
 
 * `generate([icap])` - create an instance based on a new random key (setting `icap` to true will generate an address suitable for the `ICAP Direct mode`)
-* `fromPrivateKey(input)` - create an instance based on a raw key
+* `fromPrivateKey(input)` - create an instance based on a raw private key
+* `fromPublicKey(input)` - create an instance based on a public key (certain methods will not be available)
 * `fromV1(input, password)` - import a wallet (Version 1 of the Ethereum wallet format)
 * `fromV3(input, password, [nonStrict])` - import a wallet (Version 3 of the Ethereum wallet format). Set `nonStrict` true to accept files with mixed-caps.
 * `fromEthSale(input, password)` - import an Ethereum Pre Sale wallet
diff --git a/index.js b/index.js
index 3f94b01..43e7564 100644
--- a/index.js
+++ b/index.js
@@ -13,13 +13,30 @@ function decipherBuffer (decipher, data) {
   return Buffer.concat([ decipher.update(data), decipher.final() ])
 }
 
-var Wallet = function (priv) {
-  if (!ethUtil.isValidPrivate(priv)) {
+var Wallet = function (priv, pub) {
+  if (priv && !ethUtil.isValidPrivate(priv)) {
     throw new Error('Private key does not satisfy the curve requirements (ie. it is invalid)')
   }
-  this.privKey = priv
+  this._privKey = priv
+  this._pubKey = pub
 }
 
+Object.defineProperty(Wallet.prototype, 'privKey', {
+  get: function () {
+    assert(this._privKey, 'This is a public key only wallet')
+    return this._privKey
+  }
+})
+
+Object.defineProperty(Wallet.prototype, 'pubKey', {
+  get: function () {
+    if (!this._pubKey) {
+      this._pubKey = ethUtil.privateToPublic(this.privKey)
+    }
+    return this._pubKey
+  }
+})
+
 Wallet.generate = function (icapDirect) {
   if (icapDirect) {
     while (true) {
@@ -42,7 +59,7 @@ Wallet.prototype.getPrivateKeyString = function () {
 }
 
 Wallet.prototype.getPublicKey = function () {
-  return ethUtil.privateToPublic(this.privKey)
+  return this.pubKey
 }
 
 Wallet.prototype.getPublicKeyString = function () {
@@ -50,7 +67,7 @@ Wallet.prototype.getPublicKeyString = function () {
 }
 
 Wallet.prototype.getAddress = function () {
-  return ethUtil.privateToAddress(this.privKey)
+  return ethUtil.publicToAddress(this.pubKey)
 }
 
 Wallet.prototype.getAddressString = function () {
@@ -63,6 +80,8 @@ Wallet.prototype.getChecksumAddressString = function () {
 
 // https://github.com/ethereum/wiki/wiki/Web3-Secret-Storage-Definition
 Wallet.prototype.toV3 = function (password, opts) {
+  assert(this._privKey, 'This is a public key only wallet')
+
   opts = opts || {}
   var salt = opts.salt || crypto.randomBytes(32)
   var iv = opts.iv || crypto.randomBytes(16)
@@ -140,6 +159,10 @@ Wallet.prototype.toV3String = function (password, opts) {
   return JSON.stringify(this.toV3(password, opts))
 }
 
+Wallet.fromPublicKey = function (pub) {
+  return new Wallet(null, pub)
+}
+
 Wallet.fromPrivateKey = function (priv) {
   return new Wallet(priv)
 }
diff --git a/test/index.js b/test/index.js
index 312bd57..a2fe899 100644
--- a/test/index.js
+++ b/test/index.js
@@ -52,6 +52,27 @@ describe('.getChecksumAddressString()', function () {
   })
 })
 
+describe('public key only wallet', function () {
+  var pubKey = new Buffer('5d4392f450262b276652c1fc037606abac500f3160830ce9df53aa70d95ce7cfb8b06010b2f3691c78c65c21eb4cf3dfdbfc0745d89b664ee10435bb3a0f906c', 'hex')
+  it('.fromPublicKey() should work', function () {
+    assert.equal(Wallet.fromPublicKey(pubKey).getPublicKey().toString('hex'),
+      '5d4392f450262b276652c1fc037606abac500f3160830ce9df53aa70d95ce7cfb8b06010b2f3691c78c65c21eb4cf3dfdbfc0745d89b664ee10435bb3a0f906c')
+  })
+  it('.getAddress() should work', function () {
+    assert.equal(Wallet.fromPublicKey(pubKey).getAddress().toString('hex'), 'b14ab53e38da1c172f877dbc6d65e4a1b0474c3c')
+  })
+  it('.getPrivateKey() should fail', function () {
+    assert.throws(function () {
+      Wallet.fromPublicKey(pubKey).getPrivateKey()
+    })
+  })
+  it('.toV3() should fail', function () {
+    assert.throws(function () {
+      Wallet.fromPublicKey(pubKey).toV3()
+    })
+  })
+})
+
 describe('.generate()', function () {
   it('should generate an account', function () {
     assert.equal(Wallet.generate().getPrivateKey().length, 32)