It is very possible that this is too slow for you. Please let me know what kinds of performance you're seeing.
You must install sjcl as well as rncryptor-js. Note that plaintext and ciphertext are sjcl.bitArrays, not as strings. It is currently up to you to convert.
SJCL (1.0.0) config: ./configure --without-all --with-aes --with-bitArray --with-codecHex --with-sha256 --with-sha1 --with-hmac --with-pbkdf2 --with-random --with-convenience --with-cbc