text: #ifndef _AES_H_
  #define _AES_H_
  
  #include <stdint.h>
  
  //resource code url: https://github.com/kokke/tiny-AES-c
  
  // #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_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(struct AES_ctx* ctx, uint8_t* buf);
  void AES_ECB_decrypt(struct AES_ctx* ctx, uint8_t* buf);
  int AES_ECB_PKSC5PaddingParse16(unsigned char *src);
  int  AES_ECB_encryptwithPKSC5Padding16(unsigned char *aesKey, unsigned char *src, unsigned short srcLen, unsigned char *dst);
  
  #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_
  