Why Is Symmetric Key Encryption So Much Faster Than Asymmetric (Public) Key?
Remember as a child when you said something that your teachers or parents said, “That’s a silly question. It just is!”. Well, children often ask some of the best questions, as they often don’t take things for granted. As a good innovator and/or researcher, you need to continually ask question, and, especially, for things that might seem obvious.
So, why is symmetric key so much faster than asymmetric key. Well, asymmetric key encryption uses fairly large prime numbers, and which makes the operations fairly complex. In RSA, for example, we have to operate with a modulus, and which is often made up to two 1,024 bit prime numbers. The values we must process then up having 2,048 bits. We thus need many operations just to compute a single value.
In symmetric key encryption, such as with AES, we use a much simplier way of operating on our data: Galois Fields (GF). With this, we can constrain the values we operate on to just 4 or 8 bits. Every operation with have in a GF, such as for add, subtract and multiply, can be easily reversed, such as for subtract, add and divide. Thus in symmetric key, we might multiply by a given value (and use a part of our encryption key) and then to decrypt we can then divide by the same value (and the same part of the key). The division is actually done by finding…
