doc: update crypto cipher/decipher docs

doc/api/crypto.markdown

@@ -111,16 +111,19 @@ Creates and returns a cipher object, with the given algorithm and password.
 `algorithm` is dependent on OpenSSL, examples are `'aes192'`, etc.
 On recent releases, `openssl list-cipher-algorithms` will display the
 available cipher algorithms.
-`password` is used to derive key and IV, which must be `'binary'` encoded
-string (See the [Buffer section](buffer.html) for more information).
+`password` is used to derive key and IV, which must be a `'binary'` encoded
+string or a [buffer](buffer.html).
 
 ## crypto.createCipheriv(algorithm, key, iv)
 
 Creates and returns a cipher object, with the given algorithm, key and iv.
 
-`algorithm` is the same as the `createCipher()`. `key` is a raw key used in
-algorithm. `iv` is an Initialization vector. `key` and `iv` must be `'binary'`
-encoded string (See the [Buffer section](buffer.html) for more information).
+`algorithm` is the same as the argument to `createCipher()`.
+`key` is the raw key used by the algorithm.
+`iv` is an [initialization
+vector](http://en.wikipedia.org/wiki/Initialization_vector).
+
+`key` and `iv` must be `'binary'` encoded strings or [buffers](buffer.html).
 
 ## Class: Cipher