The DES algorithm is one of the most commonly used key block ciphers that are symmetric today. It is used to transmit data, store data and authentication. Although it was developed in the 1970s it has been used as the basis for many modern encryption algorithms and is considered to be secure enough to protect payment card and banking transactions.
During DES encryption the process starts by changing the plaintext to 64 bits by a series of steps, which include initial permutations and rounds of operations. The final permutation is then carried out. Each step alters bits by changing them in different ways, creating a level confusion and a spread that makes it harder for hackers to break into the ciphers.
In the initial stage, a function known as Initial Permutation (IP) alters the bits of the block into two permuted portions known as Left Plain Text or LPT and Right Plain Text or RPT. This process alters the initial plain text of 64 bits, making it harder to break.
The RPT and LPT will then be combined and then run through 16 rounds DES operations. The resultant 64-bit encrypted text is then subjected to a final permutation that is similar to the original, but reversed.
This makes it very difficult to break the cipher. It is also much faster in hardware than in software, and this speed is an important benefit in certain applications where encryption must be done in real-time. Although theoretical attacks have been carried out using DES the most practical strategy was a brute-force attack that required huge computing power, but took a long time to complete.