Note: A symmetric encryption method has one key that can be used for encryption and decryption of the message. Although faster, it is less secure than an asymmetric encryption method wherein one key used to encrypt the message is made public but the key to decode the message is private.
1. Advanced Encryption Standard
AES is a symmetric encryption method, wherein the key used is 128, 192, or 256 bits long. The smaller the key, the less ’rounds’ it takes to encrypt the message. In each round, AES performs several steps of substitution, transposing and mixing in the message. AES is by far the most common encryption method.
2. Triple Data Encryption Standard
Triple DES is another symmetric encryption method and is a successor to the DES method. Data is encrypted with three 56-bit keys, hence the ‘Triple’ part. Triple DES is usually used for ATM PINs.
3. Twofish
Twofish is also a symmetric encryption method, and it encrypts messages with 128 bits (twice the amount of Blowfish, what it was based on, which uses 64 bits). Twofish always encrypts data in 16 rounds, making it slower than AES but secure.
Exchanging keys to communicate across a public channel
Diffie-Hellman key exchange is a way to communicate across a public channel securely. Basically, one person has keys A and B, and another person has keys C and D. A times C will equal Key E, and B times D will also equal E. Key E is used as the key to share messages (symmetrically; one person encrypts a message with E and the other person decodes it with E). One of each person’s keys will be private and the other will be public.