The DES algorithm was widely used following its adoption as the standard for federal encryption in 1977. It was soon plagued by security issues, and the advent of more computing power drew new evidence of its weaknesses. Eventually, DES was sidelined for the more sophisticated AES algorithm.

DES uses a block size of 64 bits to break plaintext down into smaller pieces that are processed by the algorithm over 16 rounds. Each round is a series five different processes. The process starts with a permutation that rearranges the bits of data in blocks, leading to jumbled data. Then comes the expansion, key mixing and a final permutation to produce the encrypted.

Each round also has an XOR operation, which makes use of the output of one round as input for the next. This XOR operation confuses the relationship between plaintext (plaintext) and ciphertext (ciphertext) and makes it more difficult for attackers discover the secret key which will create the correct ciphertext.

The DES algorithm uses S-boxes as well to further disperse the data. This makes it more difficult for hackers and attackers to distinguish between bits that are plaintext and which are encrypted. In the last round of each round, the expanded text is XORed with a 48-bit key that is generated from the previous round’s key. This gives additional protection against brute force attacks.