1. Encryption is a way of mangling data so that an unauthorized party cannot understand it. Encryption applies mathematical operations to data in order to render it incomprehensible. The only way to read the data is apply the reverse mathematical operations. In technical speak, encryption is applies mathematical algorithms with a key that converts plaintext to ciphertext. Only someone in possession of the key can decrypt the message. Analogy: Some aliens come down to earth and give you a safe, and a key to the lock. For purposes of this discussion, the aliens use some magic technology that is beyond our human understanding, and that we will never be able to break into the safe. You steal something, put it into the safe, and lock it up with the key. You hide the key. The police arrest you and confiscate the safe. The only way the police will ever recover this stolen object is when you give them the key. Encryption is the same way; it creates an unbreakable box that you can put data in that nobody can ever get back out unless they have the appropriate key. Controversy: Encryption has massive philosophical implications when put into widespread use. It means that citizens can hide their data from governments (especially repressive ones) and law enforcement (especially when you are committing a crime). This has the potential of making governments more accountable to the populace. It likewise has the potential of making crime easier. Key point: Encryption tends to be the strongest link in the chain. When encryption is cracked, it is usually through some other weakness like key distribution or weak passwords. Contrast: Asymmetric encryption uses different keys for encryption and decryption. Since the most useful form of this is one you keep one key private and make the other public, this is better known as public key encryption. In contrast, symmetric encryption uses the same key for both encryption and decryption. Notes: Some algorithms popular in cryptography are: DES, rc4 Some popular applications that use encryption are: PGP, web browsers. Some protocols that use encryption are: SSL, IPsec From Hacking-Lexicon