Decryptor/Decryptor/SymmetricEncryptionBox.cpp

#include "Openssl_crypto.h"
#include "SymmetricEncryptionBox.h"

  // increments last 4 bytes (in big-endian order)
  uint32_t SymmetricEncryptionBox::aes_gcm_increment_iv_internal_call(uint8_t* iv)  {
  	uint32_t counter;
  	for(counter=11;counter>7;counter--)
  	{
  		if(iv[counter] == 0xff)
  		{
  			if(counter - 1 == 7)
  				return 0xff;
  			iv[counter-1] = 0x01;
  			iv[counter] = 0x0;
  		}
  		else
  			iv[counter] += 1;
  	}
  	return 0;
  }


  void SymmetricEncryptionBox::set_symmetric_key(uint8_t* given_key)
  {
    uint32_t counter;
    for(counter=0; counter<16; counter++)
      symmetric_key[counter] = given_key[counter];
  }

    void SymmetricEncryptionBox::get_symmetric_key(uint8_t* op_key)
    {
	    uint32_t counter;
	    for(counter=0; counter<16; counter++)
	      op_key[counter] = symmetric_key[counter];
    }

  // TODO: IMPORTANT - CHECK IF WE NEED TO DO THE AES GCM INCREMENT IV FOR DECRYPTION TOO.
  uint32_t SymmetricEncryptionBox::encrypt_decrypt(int enc, uint8_t* plaintext, uint32_t plaintext_length, uint8_t* ciphertext, uint32_t* ciphertext_length)
  {
    uint8_t tag[16];uint32_t counter;
    if(enc == 0)
	{
		for(counter=0;counter<16;counter++)
			tag[counter] = plaintext[counter + plaintext_length]; 
	}
    uint32_t return_status = aes_gcm_128(enc, symmetric_key, iv, plaintext, plaintext_length, ciphertext, ciphertext_length, tag);
	if(enc == 1)
	{
		for(counter=0;counter<16;counter++)
			ciphertext[counter + *ciphertext_length] = tag[counter];
		*ciphertext_length=*ciphertext_length + 16;
	}
    if(return_status == 0)
      aes_gcm_increment_iv_internal_call(iv);
    return return_status;
  }