DES is an abbreviation to Data Encryption Standard, which is a Block Cipher that was developed by IBM. DES encrypts block by block with size of 64 bits each block; and uses a key size of 56 bits. This is a symmetric cipher, which uses the same key to encryption and decryption. DES is implemented 16 rounds, where each round is performed via the same operation. Note: The Different sub-key in each round derived from main key. The figure below shows the DES operation.
Fact: DES is considered insecure, nowadays, due to the small key length of 56 bits. However, a new technique that is called 3DES is considered to be very secure.
3DES is a Triple Data Encryption Standard that works with two keys. Each key has a size of 56 bits; with a strength size of 112 bits. 3DES is used in electronic payments such as, (Chip and PIN). There is no current cryptanalysis attack on 3DES. The figure below shows the 3DES operation.
3DES operation is still widely used today. However, it was replaced with an advance operation called Advanced Encryption Standard (AES) in 2000.