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// This file is part of the CircuitPython project: https://circuitpython.org

// SPDX-License-Identifier: MIT

#pragma once

#include <stdint.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 1

#endif

#ifndef CTR

#define CTR 1

#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_KEYLEN256 32

#define AES_keyExpSize256 240

#endif

#if defined(AES192) && (AES192 == 1)

#define AES_KEYLEN192 24

#define AES_keyExpSize192 208

#endif

#if defined(AES128) && (AES128 == 1)

#define AES_KEYLEN128 16 // Key length in bytes

#define AES_keyExpSize128 176

#endif

struct AES_ctx

{

union {

#if defined(AES256) && (AES256 == 1)

uint8_t RoundKey256[AES_keyExpSize256];

#endif

#if defined(AES192) && (AES192 == 1)

uint8_t RoundKey192[AES_keyExpSize192];

#endif

#if defined(AES128) && (AES128 == 1)

uint8_t RoundKey128[AES_keyExpSize128];

#endif

};

#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))

uint8_t Iv[AES_BLOCKLEN];

#endif

uint32_t KeyLength;

uint8_t Nr;

uint8_t Nk;

};

void AES_init_ctx(struct AES_ctx *ctx, const uint8_t *key, uint32_t keylen);

#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))

void AES_init_ctx_iv(struct AES_ctx *ctx, const uint8_t *key, uint32_t keylen, 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)

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