International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Data Encryption Standard (DES) was developed in 1977 by IBM for the National Bureau of Standards (NBS) as a standard way to encrypt unclassified data for security protection. When the DES decrypts the encrypted data blocks, it assumes that there are no bit errors in the data blocks. It is the object of this project to determine the Hamming distance between the original data block and the data block after decryption if there occurs a single bit error anywhere in the encrypted bit block of 64 bits. This project shows that if a single bit error occurs anywhere in the 64-bit encrypted data block, a mean Hamming distance of 32 with a standard deviation of 4 is produced between the original bit block an the decrypted bit block. Furthermore, it is highly recommended by this project to use a forward error correction scheme like BCH (127, 64) or Reed-Solomon (127, 64) so that the probability of this bit error occurring is decreased.