Encryption Algorithms - Symmetric key-based

Symmetric or Secret Key Encryption

Symmetric key Encryption, often called secret-key or private-key encryption is simpler than public-key encryption (PKI) in that there is only 1 key but it is more complicated than PKI in that a private key must be distributed across an untrusted network before an encrypted transmission can occur. Symmetric key cryptography requires much less computing power to implement so it is well suited for deployment in situations where we have an established connection that must be encrypted over a public network.

Symmetric key encryption can be divided into the following two categories:

Block ciphers - Takes a block of bits (usually 64 bits) and encrypts them as a single unit. Block ciphers are slower but are considered more secure than stream ciphers.
Stream ciphers - Encrypts data a single bit at a time.

| Block Ciphers | Stream Ciphers |  

Data Encryption Standard - DES

DES was invented in the late 1970's by the NIST It is a block cipher using a 56-bit key on each 64-bit block of cleartext data. DES has been broken for a long time.

| DES |  

Triple DES - 3DES

An enhancement of DES where each block of data is encrypted three times with a 56-bit key effectively giving a 168-bit key, which is quite a good bit-strength key.

| 3DES |  

Advanced Encryption Standard - AES

Also called Rijndael, it is a block cipher that has been chosen by NIST to be the successor to DES. It can create keys from 128 to 256-bit in length and can perform the encryption on up to 128-bit blocks of clear-text at a time. (DES is limited to 64-bit blocks). Similar to 3DES the blocks are passed to 3 layers, each layer performs a different task. Each pass encrypts the data and generates a key and the final key is applied to the ciphertext data.

Rijndael (AES) is a shared-key (symmetric) block cipher, supporting variable length blocks and variable key size, invented by Joan Daemen and Vincent Rijmen.

Blowfish Encryption Algorithm

A block cipher with any size block of cleartext and any key size up to 448-bits.

International Data Encryption Algorithm - IDEA

Created in the early 1990's after being called PES and then IPES it was finally named IDEA after some final revisions. It encrypts 64-bit blocks with a 128-bit key strength cipher.

| IDEA |  

Rivest Cipher - RC2-6

Common in commercial applications, the Rivest cipher is a series of encryption algorithms, each implementation of RCx has a different algorithm and diffrent bit strengths on the keys. See the table.

| RC2 | RC4 | RC5 and 6 |  

MARS

MARS, a shared-key (symmetric) block cipher, supporting 128-bit blocks and variable key size, invented by IBM.

Symmetric Key Algorithms

Algorithm	Cipher Type	Key Length (bit strength)
AES (Rinjadel)	128 bit Block	128, 192 or 256 bits
DES	Block	56 bits
3DES	Block	168 bits
Blowfish	Block	1-448 bits
IDEA	Block	128 bits
RC2	Block	1-2048 bits
RC4	Stream	1-2048 bits
RC5	Block	128-256 bits
RC6	Block	128-256 bits
Twofish	Block	128-256
Skipjack (RFC2876)	64 Bit Block	80 bits