crypto: error messages.

lib/crypto/crypto.js

@@ -294,6 +294,12 @@ crypto.encrypt = co(function* encrypt(data, passphrase, iv) {
 crypto.encipher = function encipher(data, key, iv) {
   var cipher;
 
+  assert(Buffer.isBuffer(data));
+  assert(Buffer.isBuffer(key));
+  assert(Buffer.isBuffer(iv));
+  assert(key.length === 32);
+  assert(iv.length === 16);
+
   if (!nodeCrypto)
     return aes.cbc.encrypt(data, key, iv);
 
@@ -340,6 +346,28 @@ crypto.decrypt = co(function* decrypt(data, passphrase, iv) {
  */
 
 crypto.decipher = function decipher(data, key, iv) {
+  assert(Buffer.isBuffer(data));
+  assert(Buffer.isBuffer(key));
+  assert(Buffer.isBuffer(iv));
+  assert(key.length === 32);
+  assert(iv.length === 16);
+  try {
+    return crypto._decipher(data, key, iv);
+  } catch (e) {
+    throw new Error('Bad key for decryption.');
+  }
+};
+
+/**
+ * Decrypt with aes-256-cbc.
+ * @private
+ * @param {Buffer} data
+ * @param {Buffer} key
+ * @param {Buffer} iv
+ * @returns {Buffer}
+ */
+
+crypto._decipher = function decipher(data, key, iv) {
   var decipher;
 
   if (!nodeCrypto)