One of the earliest encryption standard is DES.
Designed in the 1970s by IBM, with some input from the US National Security Agency
DES was adopted as an official FIPS for the US.
Federal Information Processing Standard
DES is a symmetric block cipher that uses 64-bit key sizes and operates on blocks 64-bits in size.
Though the key size is technically 64-bits in length, 8-bits are used only for parity checking, a simple form of error checking. This means that real world key length for DES is only 56-bits.
Key length is super important in cryptography since it essentially defines the maximum potential strength of the system.
If an algorithm is an ideal algorithm with no flaws, the only way to attack the encryption would be to target the key. Guess the key with brute force method.
Possible number of keys with 56 bit would result in 2^56 = 72,000,000,000,000,000
In 1993, EFF have decrypted a DES encrypted message only in 56 hours.
In 1997, NIST, National Institute of standards and Techonlogy wanted to replace DES with a new algorithm. In 2001, adopted AES, Advanced Encryption Standard after an international competition. AES is also the first and only public cipher that’s approved for use with top secret information by the United States NSA.
AES uses 128 bit, 192 bit, or 256 bit.
An important thing to keep in mind when considering various encryption algorithms is speed and ease of implementation.
Complicated implementation could lead to bugs and loss of security. Speed is important
Modern CPUs from the intel and amd have AES instruction built into the CPU themselves allowing far greater computational speed and efficiency
RC4 (Rivest Cipher 4)