# What are the minimum mathematics and computer science subjects that I need to understand DES and AES?

I want to study the DES and AES algorithms

The question:

What are the minimum mathematics and computer science subjects that I need to understand DES and AES?

Edit: I mean how they work internally.

• Do you mean how they work internally, or what block ciphers in general do? Aug 5, 2021 at 22:06
• @poncho I mean how it works internally. Aug 5, 2021 at 22:34

AES uses Polynomial Modular arithmetic in Finite Fields. These are used in the SubBytes & the MixColumns Steps.

I don't think DES uses any advanced mathematics Probability Theory for both DES & AES

So you need to understand basic Linear Algebra, Group Theory (what is a Finite Field, Ring Theory), Elementary Number Theory (Modular Arithmetic).

In Comp Science, you would need an understanding of bitwise operations.

If you want to go for a deep analysis, you would need to know Information Theory, Complexity Analysis.

UPDATE: From SAI Peregrinus in the comments:

Probability theory is also required to understand how cryptanalysis works. DES's special feature was resistance to differential cryptanalysis, so you can't really understand why DES and AES have the s-boxes they do without knowing this

• Probability theory is also required to understand how cryptanalysis works. DES's special feature was resistance to differential cryptanalysis, so you can't really understand why DES and AES have the s-boxes they do without knowing this. Aug 6, 2021 at 3:24
• @SAIPeregrinus updated Aug 6, 2021 at 3:31