Oracle PL/SQL for DBAs

Encryption Components

Let’s summarize what we have learned so far. An encryption system has several basic components, as shown in Figure 4-1.

• The algorithm

• The key

• The type of encryption (symmetric, in this case, because the same key is used both to encrypt and to decrypt)

Figure 4-1. Symmetric encryption components

Let’s assume that a thief intent on stealing my laptop is trying to open the lock. What does she need in order to succeed? First, she has to know the algorithm; let’s assume here that that she knows it, perhaps because I boasted about my cleverness at work, or she read this book, or this algorithm is public knowledge. Second, she needs to learn the key. That is something I can protect. Even if the thief knows about the algorithm, I can still hide the key effectively. But as there are only 4 digits in the key, it takes only up to 10⁴, or 10,000, attempts by the thief to guess the key. And because each attempt has an equal probability of getting it right or wrong, in theory, the thief has a 1 in 5,000 chance to guess the right key. Can she do it? In this case, the thief will have to manually turn the wheels of the combination lock 5,000 times. That’s daunting, but theoretically possible. Suddenly, I don’t feel so secure anymore.

What are the ways that I can protect my lock combination?

• I can hide the algorithm.

• I can make the key difficult to guess.

• I can take both of these steps ...