We usually call it private-key encryption where sender and receiver share the same secret key. In other words, the same key used in both encryption and decryption. The longest the key the stronger the encryption. Typical key lengths are 40-256 bits where key lengths greater or equal to 80 bits can be trusted and key lengths of less than 80 bits are considered weak, regardless of the strength of the algorithm. Symmetric algorithms are usually fast and are based on simple mathematical operations. Examples of symmetric encryption algorithm are DES, 3DES, AES, IDEA, RC2/4/5/6, and Blowfish.
Data Encryption Standard (DES) - It takes as input a 64 bit key, of which only 56 bits are used. From these 56 bits, 16 48 bit subkeys are created. The message is divided into 64 bit chunks, and a complex series of steps enciphers the message using each subkey.
Triple DES - It is very similar to DES, except everything is done three times. So triple DES expects 24 bytes (192bit) key, of which 168 bits are used. Every eight bytes of the message are operates on three times (encrypt, decrypt, encrypt) before being appended to the result.
RC2 - Designed as a drop-in replacement for DES, RC2 is a variable key-sized cipher.
RC4 - Often used in file encryption products, as well as for secure communication, such as in Secure Socket Layer (SSL), RC4 is a variable key-size stream cipher.
RC5 - This fast block cipher has a variable block size and variable key length. With its 64-bit block size, it may be used as a drop-in replacement for DES.
RC6 - Based on RC5, this block cipher has as its main design goal meeting the requirement of AES.
Data Encryption Standard (DES) - It takes as input a 64 bit key, of which only 56 bits are used. From these 56 bits, 16 48 bit subkeys are created. The message is divided into 64 bit chunks, and a complex series of steps enciphers the message using each subkey.
Triple DES - It is very similar to DES, except everything is done three times. So triple DES expects 24 bytes (192bit) key, of which 168 bits are used. Every eight bytes of the message are operates on three times (encrypt, decrypt, encrypt) before being appended to the result.
RC2 - Designed as a drop-in replacement for DES, RC2 is a variable key-sized cipher.
RC4 - Often used in file encryption products, as well as for secure communication, such as in Secure Socket Layer (SSL), RC4 is a variable key-size stream cipher.
RC5 - This fast block cipher has a variable block size and variable key length. With its 64-bit block size, it may be used as a drop-in replacement for DES.
RC6 - Based on RC5, this block cipher has as its main design goal meeting the requirement of AES.
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