aes.c File Reference

#include "aes.h"

Functions
void	AddRoundKey (uint8_t *state, uint8_t round)
	Performs Add RoundKey operation. More...
aes_ret_status_t	aes_cipher (uint8_t *plainText, uint8_t *state)
	Performs AES-128 Encryption. More...
void	aes_init (uint8_t *key)
	Performs Key Expansion. More...
aes_ret_status_t	aes_inverse_cipher (uint8_t *cipherText, uint8_t *state)
	Performs AES-128 Decryption. More...
void	Inv_AddRoundKey (uint8_t *state, uint8_t round)
	Performs AddRound Key. More...
void	Inv_MixColumns (uint8_t *state, uint8_t round)
	Performs Inverse Mix Columns operation. More...
void	Inv_ShiftRows_SubBytes (uint8_t *state)
	Performs Inverse of sub bytes (from inverse sub-box) and shift rows operation. More...
void	KeyExpansion (uint8_t *round_key, uint8_t *key)
	Performs key expansion to generate key schedule from initial set of Key of 4 words. More...
void	MixColumnns (uint8_t *state)
	Performs Mix Columns Operation. More...
void	SubBytes_ShiftRows (uint8_t *state)
	Performs Sub Byte (from sbox array) and Shift rows operation. More...
uint8_t	xtime (uint8_t value)
	xtime calculation The value is multiplied by 0x02. This is implemented at the byte level as a left shift and XOR with 0x1b if the MSB of the value (before) shifting is 1. More...

Variables
bool	aes_key_ready = false
uint8_t	inv_sbox [256]
uint8_t	key_schedule [AES_KEY_SCHEDULE_SIZE]
uint8_t	RCon [11]
uint8_t	sbox [256]
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void AddRoundKey	(	uint8_t *	state,
		uint8_t	round
	)

Performs Add RoundKey operation.

Parameters

state

variable to store the intermediate result of the algorithm

References key_schedule.

Referenced by aes_cipher().

aes_ret_status_t aes_cipher	(	uint8_t *	plainText,
		uint8_t *	state
	)

Performs AES-128 Encryption.

Parameters

plainText	Input plain text block
state	Variable to store the intermediate result

Return values

ERR_NO_KEY	if key expansion is not done via aes_init()
STATUS_OKAY	if aes_init() is called before this function.

References AddRoundKey(), AES_BLOCK_SIZE, aes_key_ready, ERR_NO_KEY, key_schedule, MixColumnns(), STATUS_OKAY, and SubBytes_ShiftRows().

Referenced by cbc_encrypt(), cfb_decrypt(), cfb_encrypt(), ctr_encrypt_decrypt(), ecb_encrypt(), ofb_decrypt(), and ofb_encrypt().

void aes_init

(

uint8_t *

key

)

Performs Key Expansion.

Parameters

key	Initial Key vectors received from user

References aes_key_ready, key_schedule, and KeyExpansion().

Referenced by main().

aes_ret_status_t aes_inverse_cipher	(	uint8_t *	cipherText,
		uint8_t *	state
	)

Performs AES-128 Decryption.

Parameters

cipherText	Input cipher text block
state	Variable to store the intermediate result

Return values

ERR_NO_KEY	if key expansion is not done vis aes_init()
STATUS_OKAY	if aes_init() is called before this function.

References AES_BLOCK_SIZE, aes_key_ready, ERR_NO_KEY, Inv_AddRoundKey(), Inv_MixColumns(), Inv_ShiftRows_SubBytes(), key_schedule, and STATUS_OKAY.

Referenced by cbc_decrypt(), and ecb_decrypt().

void Inv_AddRoundKey	(	uint8_t *	state,
		uint8_t	round
	)

Performs AddRound Key.

Parameters

state

variable to store the intermediate result of the algorithm

Note

inverse of Add round key and Add round key are same.Two separate functions are defined for ease of understanding the encryption and decryption process.

References key_schedule.

Referenced by aes_inverse_cipher().

void Inv_MixColumns	(	uint8_t *	state,
		uint8_t	round
	)

Performs Inverse Mix Columns operation.

Parameters

state	variable to store the intermediate result of the algorithm
Number	of current ongoing round in AES algorithm

References xtime().

Referenced by aes_inverse_cipher().

void Inv_ShiftRows_SubBytes

(

uint8_t *

state

)

Performs Inverse of sub bytes (from inverse sub-box) and shift rows operation.

Performs Inverse of sub bytes and shift rows operation.

Parameters

state

variable to store the intermediate result of the algorithm

References inv_sbox.

Referenced by aes_inverse_cipher().

void KeyExpansion	(	uint8_t *	round_key,
		uint8_t *	key
	)

Performs key expansion to generate key schedule from initial set of Key of 4 words.

Parameters

round_key	Holds the pointer to store key schedule
key	Initial Key received from the user

References AES_NUM_OF_ROUNDS, RCon, and sbox.

Referenced by aes_init().

void MixColumnns

(

uint8_t *

state

)

Performs Mix Columns Operation.

Parameters

state

variable to store the intermediate result of the algorithm

References xtime().

Referenced by aes_cipher().

void SubBytes_ShiftRows

(

uint8_t *

state

)

Performs Sub Byte (from sbox array) and Shift rows operation.

Performs Sub Byte and Shift rows operation.

Parameters

state

variable to store the intermediate result of the algorithm

References sbox.

Referenced by aes_cipher().

uint8_t xtime

(

uint8_t

value

)

xtime calculation The value is multiplied by 0x02. This is implemented at the byte level as a left shift and XOR with 0x1b if the MSB of the value (before) shifting is 1.

Parameters

value

Value for which multiplication to be done

Referenced by Inv_MixColumns(), and MixColumnns().

bool aes_key_ready = false

Referenced by aes_cipher(), aes_init(), and aes_inverse_cipher().

uint8_t inv_sbox[256]

Initial value:

= {
    
    0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,  
    0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,  
    0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,  
    0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,  
    0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,  
    0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,  
    0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,  
    0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,  
    0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,  
    0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,  
    0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,  
    0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,  
    0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,  
    0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,  
    0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,  
    0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d   
}

Referenced by Inv_ShiftRows_SubBytes().

uint8_t key_schedule[AES_KEY_SCHEDULE_SIZE]

Referenced by AddRoundKey(), aes_cipher(), aes_init(), aes_inverse_cipher(), and Inv_AddRoundKey().

uint8_t RCon[11]

Initial value:

= {
    0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36
}

Referenced by KeyExpansion().

uint8_t sbox[256]

Initial value:

=   { 
    
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,  
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,  
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,  
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,  
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,  
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,  
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,  
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,  
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,  
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,  
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,  
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,  
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,  
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,  
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,  
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16   
}

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Referenced by KeyExpansion(), and SubBytes_ShiftRows().