Implement feature #443

src/key.js

@@ -365,6 +365,27 @@ Key.prototype.getEncryptionKeyPacket = function() {
   return null;
 };
 
+/**
+ * Encrypts all secret key and subkey packets
+ * @param  {String} passphrase
+ * @return {Boolean} true if all key and subkey packets encrypted successfully
+ */
+Key.prototype.encrypt = function(passphrase) {
+  if (this.isPrivate()) {
+    var keys = this.getAllKeyPackets();
+    for (var i = 0; i < keys.length; i++) {
+      try {
+        keys[i].encrypt(passphrase);
+      } catch (e) {
+        return false;
+      }
+    }
+  } else {
+    throw new Error("Nothing to encrypt in a public key");
+  }
+  return true;
+};
+
 /**
  * Decrypts all secret key and subkey packets
  * @param  {String} passphrase

test/general/key.js

@@ -706,5 +706,24 @@ var pgp_desktop_priv =
     }).catch(done);
   });
 
+  it('Encrypt key with new passphrase', function(done) {
+    var userId = 'test <a@b.com>';
+    var opt = {numBits: 512, userIds: userId, passphrase: 'passphrase'};
+    if (openpgp.util.getWebCryptoAll()) { opt.numBits = 2048; } // webkit webcrypto accepts minimum 2048 bit keys
+    openpgp.generateKey(opt).then(function(key) {
+      key = key.key;
+      var armor1 = key.armor();
+      var armor2 = key.armor();
+      expect(armor1).to.equal(armor2);
+      expect(key.decrypt('passphrase')).to.be.true;
+      expect(key.encrypt('new_passphrase')).to.be.true;
+      expect(key.decrypt('passphrase')).to.be.false;
+      expect(key.decrypt('new_passphrase')).to.be.true;
+      var armor3 = key.armor();
+      expect(armor3).to.not.equal(armor1);
+      done();
+    }).catch(done);
+  });
+
 });