User Manual

Enterprise Self-Encrypting Drive User’s Guide, Rev. B 4
1.1 The fundamentals of data encryption
Before we get into the specifics of Self-Encrypting Drives (SEDs) we need to have a working understanding of the
encryption process. What is it and how does it work?
1.1.1 Encryption basics
Encryption is a process whereby a plain text or clear text message is disguised in such a way as to hide its meaning. It
stands to reason that this would not be a particularly clever thing to do unless the process could be reversed and the
encrypted text (also known as cipher text) could be decrypted (or deciphered) back to the original message.
In Figure 1, we see that a clear text message is encrypted by a piece of hardware we’ll call an encryption engine and
subsequently decrypted back to the original clear text by passing it through a decryption engine. We call these
engines because they work on the data as they pass through and perform the required conversion without introduc-
ing any noticeable delay in the data flow.
Figure 1. Encryption and decryption
Both the encryption and decryption engines use a key which is the secret ingredient in the text transformation pro-
cesses. To keep things as simple as possible, this is a symmetric key, which means the same key is used for both the
encryption and the decryption process. We’re all familiar with at least one symmetric key, the one which both locks
and unlocks the door to our house.
Here’s a very simple example of symmetric encryption. Let’s suppose our encryption engine uses a very simple pro-
cess which will add incoming plain text to a secret key value, letter by letter, and output the result as cipher text. In
this case we’ll give all letters a value corresponding to their position in the alphabet such that:
“A” = 1, “B” = 2, “C” = 3, “D” = 4, ………., “Z” = 26, “ “ (space) = 27.
Now if we add “B” (2) to “G” (7) we get “I” (9). If the addition produces numbers which are greater than 27, for example
(N + R) = (14 + 18) = 32, we simply loop back around the alphabet, (32 – 27) = 5 = “E”. Suppose our clear text message
is “HELLO WORLD” and we have selected the secret encryption key “ENIGMA” (repeated as required to match the
length of the clear text message), then for our very simple encryption engine, the encryption process would provide
the following result:
HELLO WORLD + ENIGMAENIGM => MSUSAAAB SQ
Message Encryption Key Cipher Text