# Encryption and Decryption

Encryption is the transformation of information from one form (plain-text) to another (cipher-text). Encryption makes cipher-text nearly impossible to decipher without the appropriate knowledge, or key.

Decryption, the opposite of encryption, is the transformation of encrypted information (cipher-text) back into an intelligible form (plain-text).

## Key

A key in cryptology is similar to a key we use for locking and unlocking things in everyday life. In cryptography, keys are the bits and bytes used in the process of encryption and decryption. In this case, a key is a very large number that has special mathematical properties. Breaking into an encryption scheme depends on knowledge of the key or the ability to discover the key. The larger the key, the more difficult it is to discover.

Low-grade encryption uses 56 bits-this means 256 possible keys. The following might help provide a sense of scale:

- 232 is equal to 4,294,967,296 (more than 4 billion).
- 248 is equal to 281,474,976,710,656.
- 256 is equal to 72,057,594,037,927,936 (more than 72,057 trillion).

While this seems like a significant number of possibilities, present-day computers have enough processing power to make discovery a possibility and a cause for real concern-especially when low-grade encryption is in use.

## In this tutorial:

- Securing Wireless Networks
- Security Background
- Security Services
- Cryptographic Concepts and Terms
- Encryption and Decryption
- Keyspace
- Exclusive OR (XOR)
- Algorithm
- Asymmetric Encryption Algorithms
- Public-Private Key Cryptography
- Cipher
- Concealment Ciphers vs. Running Key Ciphers
- Stream Ciphers vs. Block Ciphers
- Cipher Examples
- Cipher Implementations
- Wi-Fi Protected Access
- TKIP/WPA
- Wi-Fi Protected Access 2 (WPA2)
- CCMP/AES
- Hash Functions
- EAP
- EAP Entities
- EAP Grammar
- EAP Types
- EAP-TTLS
- EAP-PSK
- EAP-SIM
- EAP-AKA
- IEEE 802.11i
- Four-Way Handshake
- IEEE 802.11i Considerations