Countermeasure: Disk Encryption

This rather long journey through encryption was important to give you a feel for how encryption works, as well as to introduce you to two of the three most widely-used encryption algorithms today, DES and AES. But do you really need to find the substitution tables and permutation tables for the algorithms and the structure of the 16 cycles just to use DES? No, no more than you need to perform your own translation from a higher-level language such as C into machine language. Tools can do that dirty work for you.

Several commercially available tools can take an entire disk, encrypt it, and return individual decrypted files as they are needed. Other tools can encrypt a single file, and still other tools can encrypt data on the fly, as for a network communication. You invoke the program, pass it the key and the data to encrypt or decrypt, and it returns your desired result. Manufacturers have made the user interface easy to use. Products are constantly being improved and new ones developed, so we will not identify any by name here, but you can easily search for and find readily available encryption tools. However, Sidebar 7-12 shows a slightly unconventional approach to compromising that encryption. As this sidebar demonstrates, an attacker can use any tools and techniques, and so the defender must remain vigilant in protecting sensitive data. Cryptography is an extremely powerful technology, but it is not a magical fairy dust that protects against all possible harm.