The DES algorithm https://dataroomnyc.com/what-is-the-data-encryption-standard/ was widely used when it became the federal encryption standard in 1977. But it was soon beset with security concerns and the introduction of increased computing power brought a fresh spotlight on its vulnerabilities. Eventually, DES was sidelined for the more advanced AES algorithm.
DES utilizes 64 bit blocks to divide plaintext into parts which are processed by the algorithm over 16 rounds. Each round consists of five different processes. The first step is a permutation that rearranges data bits inside blocks to create mixed information. Then comes the expansion, key mixing, and a final permutation to produce the encryption.
Each round also includes an XOR operation, which takes the output of one round as input for the following round. This XOR process can confuse the relationship between plaintext and ciphertext, making it more difficult for attackers to figure out the right secret key that will give the correct encrypted text.
The DES algorithm employs S-boxes as well to further disperse the data. This makes it difficult for hackers and attackers to discern which bits are plaintext and those that are ciphertext. In the final phase of each round the expanded text is XORed by using a 48-bit key that is generated from the previous round’s key. This adds an additional layer of protection against brute-force attacks.
