aes.h

/*
* The MySensors Arduino library handles the wireless radio link and protocol
* between your home built sensors/actuators and HA controller of choice.
* The sensors forms a self healing radio network with optional repeaters. Each
* repeater and gateway builds a routing tables in EEPROM which keeps track of the
* network topology allowing messages to be routed to nodes.
*
* Created by Henrik Ekblad <[email protected]>
* Copyright (C) 2013-2022 Sensnology AB
* Full contributor list: https://github.com/mysensors/MySensors/graphs/contributors
*
* Documentation: http://www.mysensors.org
* Support Forum: http://forum.mysensors.org
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* version 2 as published by the Free Software Foundation.
*
* AES implementation: https://github.com/kokke/tiny-AES-c
*/
 
#ifndef _AES_H_
#define _AES_H_
 
// #define the macros below to 1/0 to enable/disable the mode of operation.
//
// CBC enables AES encryption in CBC-mode of operation.
// CTR enables encryption in counter-mode.
// ECB enables the basic ECB 16-byte block algorithm. All can be enabled simultaneously.
 
// The #ifndef-guard allows it to be configured before #include'ing or at compile time.
#ifndef CBC
#define CBC 1
#endif
 
#ifndef ECB
#define ECB 0
#endif
 
#ifndef CTR
#define CTR 0
#endif
 
 
#define AES128 1
//#define AES192 1
//#define AES256 1
 
#define AES_BLOCKLEN 16 //Block length in bytes AES is 128b block only
 
#if defined(AES256) && (AES256 == 1)
#define AES_KEYLEN 32
#define AES_keyExpSize 240
#elif defined(AES192) && (AES192 == 1)
#define AES_KEYLEN 24
#define AES_keyExpSize 208
#else
#define AES_KEYLEN 16   // Key length in bytes
#define AES_keyExpSize 176
#endif
 
struct AES_ctx {
    uint8_t RoundKey[AES_keyExpSize];   
#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))
    uint8_t Iv[AES_BLOCKLEN];   
#endif
};
 
void AES_init_ctx(struct AES_ctx* ctx, const uint8_t* key);
#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))
void AES_init_ctx_iv(struct AES_ctx* ctx, const uint8_t* key, const uint8_t* iv);
void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv);
#endif
 
#if defined(ECB) && (ECB == 1)
// buffer size is exactly AES_BLOCKLEN bytes;
// you need only AES_init_ctx as IV is not used in ECB
// NB: ECB is considered insecure for most uses
void AES_ECB_encrypt(const struct AES_ctx* ctx, uint8_t* buf);
void AES_ECB_decrypt(const struct AES_ctx* ctx, uint8_t* buf);
 
#endif // #if defined(ECB) && (ECB == !)
 
 
#if defined(CBC) && (CBC == 1)
// buffer size MUST be mutile of AES_BLOCKLEN;
// Suggest https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7 for padding scheme
// NOTES: you need to set IV in ctx via AES_init_ctx_iv() or AES_ctx_set_iv()
//        no IV should ever be reused with the same key
void AES_CBC_encrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
 
#endif // #if defined(CBC) && (CBC == 1)
 
 
#if defined(CTR) && (CTR == 1)
 
// Same function for encrypting as for decrypting.
// IV is incremented for every block, and used after encryption as XOR-compliment for output
// Suggesting https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7 for padding scheme
// NOTES: you need to set IV in ctx with AES_init_ctx_iv() or AES_ctx_set_iv()
//        no IV should ever be reused with the same key
void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
 
#endif // #if defined(CTR) && (CTR == 1)
 
 
#endif //_AES_H_