AES-128 encryption algorithm implementation. More...

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "aes_encryption.h"

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Functions
uint8_t	s (uint8_t c)
	s is a transformation that maps an 8-bit input, c, to an 8-bit output according to the S-Box. the S-Box is a lookup table that represents the The Rijndael substitution box. More...

void	shift_rows (uint8_t block[16])
	does a circular left shift on the rows of the input 4x4 matrix. 1st row is not shifted, 2nd row is shifted 1 element, 3d row is shifted 2 elements, 4th row is shifted 3 elements. More...

uint32_t	g (uint32_t a, uint8_t round_nbr)
	g is a transformation used in the calculation of the key schedule More...

void	expand_key (uint8_t key[16], uint8_t round_nbr)
	expand_key generates the next key in the key schedule More...

uint8_t	_mult (uint8_t a, uint8_t b)
	does the multiplication of 2 elements in Galois Field GF(2^8). it can do only multiplication of any element in 0-255 by 1,2 and 3. More...

void	mix_columns (uint8_t B[16])
	performs a linear transformation on every column in the 4x4 input matrix. Every column is multiplied by the matrix below: 0x02, 0x03, 0x01, 0x01 0x01, 0x02, 0x03, 0x01 0x01, 0x01, 0x02, 0x03 0x03, 0x01, 0x01, 0x02 The multiplication is an operation in GF(2^8) which means it is not a simple multiplication of natural numbers. since there is only multiplication by 0x01, 0x02, and 0x03, a lookup table containing all the results of multiplying the values [0-256] by 0x02 and 0x03 is pre-calculated and initialized.. Multiplication by 0x01 results in the same value. More...

void	aes128_encrypt (uint8_t txt[16], uint8_t key[16])
	encrypts a block of 16 bytes (128 bits) More...

Detailed Description

AES-128 encryption algorithm implementation.

Author: Mohamed Boubaker

Function Documentation

uint8_t _mult	(	uint8_t	a,
		uint8_t	b
	)

does the multiplication of 2 elements in Galois Field GF(2^8). it can do only multiplication of any element in 0-255 by 1,2 and 3.

Parameters

uint8_t	a a value in 0-255
uint8_t	b a value in {1,2,3}

Returns: the multiplication result, which is a value in 0-256

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void aes128_encrypt	(	uint8_t	txt[16],
		uint8_t	key[16]
	)

encrypts a block of 16 bytes (128 bits)

Parameters

uint8_t	txt[16] is the input block to be encrypted
uint8_t	key[16] is the encryption key.

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void expand_key	(	uint8_t	previous_key[16],
		uint8_t	round
	)

expand_key generates the next key in the key schedule

Parameters

uint8_t	previous_key[16] is the starting key
uint8_t	next_key[16] is the newly generated key from the previous_key
uint8_t	round is the round number in the AES algorithm. values = 1-10

calculate and insert words in v. Every word represent 4 bytes from the key. every 4 bytes in the key are mapped to a 32 bit word in v

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uint32_t g	(	uint32_t	a,
		uint8_t	round_nbr
	)

g is a transformation used in the calculation of the key schedule

Parameters

uint32_t	is the input of the g transform
uint8_t	round_nbd is the AES-128 round number. 1-10

Returns: the transform of a

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void mix_columns ( uint8_t block[16] )

performs a linear transformation on every column in the 4x4 input matrix. Every column is multiplied by the matrix below: 0x02, 0x03, 0x01, 0x01 0x01, 0x02, 0x03, 0x01 0x01, 0x01, 0x02, 0x03 0x03, 0x01, 0x01, 0x02 The multiplication is an operation in GF(2^8) which means it is not a simple multiplication of natural numbers. since there is only multiplication by 0x01, 0x02, and 0x03, a lookup table containing all the results of multiplying the values [0-256] by 0x02 and 0x03 is pre-calculated and initialized.. Multiplication by 0x01 results in the same value.

Parameters

uint8_t block[16] The 16 bytes length input is regarded as a 4x4 matrix.

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uint8_t s ( uint8_t c )

s is a transformation that maps an 8-bit input, c, to an 8-bit output according to the S-Box. the S-Box is a lookup table that represents the The Rijndael substitution box.

Parameters

c	is the input

Returns: s returns the transformation value

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void shift_rows ( uint8_t block[16] )

does a circular left shift on the rows of the input 4x4 matrix. 1st row is not shifted, 2nd row is shifted 1 element, 3d row is shifted 2 elements, 4th row is shifted 3 elements.

Parameters

uint8_t block[16] The 16 bytes length input is regarded as a 4x4 matrix. The rows of this matrix will be shifted as described in the brief section.

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Functions

Detailed Description

Function Documentation