Before you do anything further, seek to understand the difference between encryption and authentication, and why you probably want authenticated encryption rather than just encryption. To implement authenticated encryption, you want to Encrypt then MAC. The order of encryption and authentication is very important! One of the existing answers to this question made this mistake; … Read more
Well, you could look it up in Wikipedia… But since you want an explanation, I’ll do my best here: Hash Functions They provide a mapping between an arbitrary length input, and a (usually) fixed length (or smaller length) output. It can be anything from a simple crc32, to a full blown cryptographic hash function such … Read more
No. MD5 is not encryption (though it may be used as part of some encryption algorithms), it is a one way hash function. Much of the original data is actually “lost” as part of the transformation. Think about this: An MD5 is always 128 bits long. That means that there are 2128 possible MD5 hashes. … Read more
Share the password (a char[]) and salt (a byte[]—8 bytes selected by a SecureRandom makes a good salt—which doesn’t need to be kept secret) with the recipient out-of-band. Then to derive a good key from this information: /* Derive the key, given password and salt. */ SecretKeyFactory factory = SecretKeyFactory.getInstance(“PBKDF2WithHmacSHA256”); KeySpec spec = new PBEKeySpec(password, … Read more
EDIT 2013-Oct: Although I’ve edited this answer over time to address shortcomings, please see jbtule’s answer for a more robust, informed solution. https://stackoverflow.com/a/10366194/188474 Original Answer: Here’s a working example derived from the “RijndaelManaged Class” documentation and the MCTS Training Kit. EDIT 2012-April: This answer was edited to pre-pend the IV per jbtule’s suggestion and as … Read more
bcrypt is a hashing algorithm which is scalable with hardware (via a configurable number of rounds). Its slowness and multiple rounds ensures that an attacker must deploy massive funds and hardware to be able to crack your passwords. Add to that per-password salts (bcrypt REQUIRES salts) and you can be sure that an attack is … Read more