Within the last decade, there has been a vast increase in the accumulation
and communication of digital computer data in both the private and public sectors.
Much of this information has a significant value, either directly or indirectly, which
requires protection. One of the most important protection methods is inventing and
developing different encryption algorithms. The algorithms uniquely define the
mathematical steps required to transform data into a cryptographic cipher and also
to transform the cipher back to the original form.
This paper introduces a new method to enhance the performance of the
Data Encryption Standard (DES) algorithm. This is done by replacing the
predefined XOR operation applied during the 16 round of the standard algorithm
by a new operation depends on using two keys, each key consists of a combination
of 4 states (0, 1, 2, 3) instead of the ordinary 2 state key (0, 1). This replacement
adds a new level of protection strength and more robustness to breaking methods.