diff --git a/package.json b/package.json
index 4bf41b4..cb8054b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "peer-id",
-  "version": "0.3.4",
+  "version": "0.4.0",
   "description": "IPFS Peer Id implementation in Node.js",
   "main": "src/index.js",
   "scripts": {
@@ -41,6 +41,7 @@
   "dependencies": {
     "bs58": "^3.0.0",
     "keypair": "^1.0.0",
-    "multihashing": "^0.2.0"
+    "multihashing": "^0.2.0",
+    "node-forge": "^0.6.38"
   }
 }
diff --git a/src/index.js b/src/index.js
index cc1e70b..f4e3cae 100644
--- a/src/index.js
+++ b/src/index.js
@@ -5,6 +5,7 @@
 var multihashing = require('multihashing')
 var base58 = require('bs58')
 var keypair = require('keypair')
+var forge = require('node-forge')
 
 exports = module.exports = Id
 
@@ -46,6 +47,10 @@ function Id (id, privKey, pubKey) {
   }
 }
 
+function fix (str) {
+  return str.replace(/\r/g, '') + '\n'
+}
+
 // generation
 
 exports.create = function () {
@@ -73,6 +78,13 @@ exports.createFromPubKey = function (pubKey) {
   return new Id(mhId, null, pubKey)
 }
 
-exports.createFromPrivKey = function () {
-  // TODO(daviddias) derive PubKey from priv
+exports.createFromPrivKey = function (privKey) {
+  var privateKey = forge.pki.privateKeyFromPem(privKey)
+  var publicKey = {
+    n: privateKey.n,
+    e: privateKey.e
+  }
+  var pubKey = fix(forge.pki.publicKeyToRSAPublicKeyPem(publicKey, 72))
+  var mhId = multihashing(pubKey, 'sha2-256')
+  return new Id(mhId, privKey, pubKey)
 }
diff --git a/tests/id-test.js b/tests/id-test.js
index 7aefb49..220e35e 100644
--- a/tests/id-test.js
+++ b/tests/id-test.js
@@ -44,6 +44,7 @@ test('Recreate from a Public Key', function (t) {
 })
 
 test('Recreate from a Private Key', function (t) {
-  // TODO
+  var id = PeerId.createFromPrivKey(testId.privKey)
+  t.ok(id)
   t.end()
 })