It implies that the Data Encryption Standard (DES), which offers a way to secure data, is implemented by the CoreDES macro. The algorithm requires 64 bits of plaintext data and 64 bits of a cipher key as inputs, using only 56 of the key's 64 bits for calculations (the least significant bit of each cipher key byte is used to provide odd-parity for the key bytes). After 16 cycles, the algorithm outputs a 64-bit ciphered version of the original plaintext data. The data bits are exposed to permutation and addition functions during the course of the algorithm's 16 cycles, or iterations, which are determined by applying rotations and permutations on the original 56-bit cipher key.
This process is repeated 16 times, with each iteration using a different subkey derived from the original cipher key. The result is a ciphertext that is also 64 bits long. DES was widely used for many years, but its security has been called into question due to advances in computing power and the discovery of vulnerabilities in the algorithm.
