# cryptography 76

explain AES crypto using mtrix multiplication

When encrypting with AES, we only need to multiply by the Galois fields for 1, 2 and 3. The interesting part about this multiplication, it is already done for us. It is everywhere on the internet. I will show you the tables in a few minutes.

A few things to remember â€“

1. Multiply a Galois field by a Galois field for 1 â€“ you get the same thing. It is like multiplying a number by 1. You get the same number back.
2. Multiply by two or three are different. The original values des change. We can multiply or we can use the look up tables.
3. There are two tables that are available MUL2 and MUL3.
4. Remember the resulting values have to be MOD 100011011 ïƒŸ Do you remember why? This is the reducer to make the result fit in a byte

Letâ€™s look at the word â€˜whatâ€™ and apply AES to it

W is a 57 in HEX â€“ represented by 0x57
h is a 68 in HEX â€“ represented by 0x68
a is a 61 in HEX â€“ represented by 0x61
t is a 74 in HEX – â€“ represented by 0x74