AES Library

Implementation of the 128-bit variant of AES (Advanced Encryption Standard) as a C Library.

Submodule - AES Python

Python implementation of AES - used as a reference for C library and testing:

• Local Directory: 'python-aes'
• Repo URL: https//github.com/boppreh/aes

References

Key references:

1. Creel, “AES Encryption Series”, YouTube, 2015-2016. Available Online
   • Easy to follow YouTube series on AES encryption in C
2. S. Trenholme, “The AES Encryption Algorithm”, Sam Trenholme’s Webpage, 2005. Available Online
   • Series of articles which describe various aspects of the Rijndael (AES) encryption algorithm.
3. Rijndael Mixcolumns, Wikipedia, Feb. 06. 2024. Available Online
   • Galois Multiplication lookup tables used in this project are available here
4. Forma Estudio, “Rijndael (AES) Animation”, Forma Estudio, 2004. Available Online
   
   
   

Main Encryption Stages:

The following is a high level description of the three main Rijndael AES encryption functions as implemented in this project:

Sub-Bytes Encryption:

• Each byte value in a block is substituted with a corresponding S-box lookup value.
• The current byte value acts as the index for S-Box to get the new byte value.
  
  
  
  
  
  

Shift-Rows Encryption:

• Each byte of each row is shifted to the left (except for the first row).
• First row: no shift
• Second row: Shift left 1 position
• Third row: Shift left 2 positions
• Fourth row: Shift left 3 positions
  
  
  
  
  
  

Mix-Columns Encryption:

• Transforms the matrix, column by column
• Each byte of each column is transformed through Matrix multiplication in Rijndael's Galois field
• This project simplifies calculations through the use of Galois multiplication lookup tables and XOR operations