aes.c

AES加解密算法的C语言实现

void Aes_KeySchedule(unsigned char *  Key, unsigned char *  W, length Keylength);
void Aes_Encryption(unsigned char *  Cipher, unsigned char *  Plain, unsigned char *  W, unsigned char Keylength);
void Aes_Decryption(unsigned char *  Plain, unsigned char *  Cipher, unsigned char *  W, unsigned char Keylength);
void Shiftrows_Subbyte(void);
void Invshiftrows_Invsubbyte(void);
void MixColumns(void);
void InvMixcolumn_end (void);
@near void xtime(unsigned char);
void Clear_AES_variables_page0(void);

#pragma section {d_aes}
unsigned char State[16]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
unsigned char State2[16]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
static unsigned char* SubKey=0;

/*Matrix Sbox for the Sbox operation in encryption procedure*/
const unsigned char SBOX[256]={  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};

/*Matrix INVSBOX for the procedure of decryption*/
const unsigned char INVSBOX[256] ={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};

const unsigned char Rcon[10] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36};




//-------------------------------------------------------------------------
// Function name 	: Aes_KeySchedule
// Purpose		: Compute the key scheduling for a 128-bit, 192-bit or 256-bit key
// Input: 
//	Key = the cipher key on Keylength.
//	W = an array on 4*(Keylength+28) bytes. 
//	Keylength is the length of the Key. It can be equal to 16 bytes (128 bits), 24 bytes (192 bits) or 32 bytes (256 bits).
// Output: W contains the key schedule.
///-------------------------------------------------------------------------
  void Aes_KeySchedule(unsigned char *  Key, unsigned char *  W, unsigned char Keylength)
{
unsigned char i;	
unsigned char j,k=0;
unsigned char Nbround;

SubKey=W;

Nbround = 4*(Keylength +28);

for (i=Keylength-1; i>0;i--) SubKey[i]=Key[i];
SubKey[0]=Key[0];

i=Keylength;
while (i < Nbround)
	{
		j=i-4;
		State[0]=State2[0]=SubKey[j++];
		State[1]=SubKey[j++];
		State[2]=SubKey[j++];
		State[3]=SubKey[j];

		if ((i % Keylength)==0)
			{
				State[0]=SBOX[State[1]] ^ Rcon[k];
				State[1]=SBOX[State[2]];
				State[2]=SBOX[State[3]];
				State[3]=SBOX[State2[0]];
				k++;
			} 	
		else if ((Keylength == 32) && (i % 32 == 16))
			{
				State[0]=SBOX[State[0]];
				State[1]=SBOX[State[1]];
				State[2]=SBOX[State[2]];
				State[3]=SBOX[State[3]];
			}
		j=i-Keylength;
		
		SubKey[i++]=State[0]^SubKey[j++];		
		SubKey[i++]=State[1]^SubKey[j++];		
		SubKey[i++]=State[2]^SubKey[j++];		
		SubKey[i++]=State[3]^SubKey[j];		
	} 
// clear intermediate results (State, State2[0],SubKey) in page 0 	
SubKey=0;
for (i=15; i>0;i--) State[i]=0;
State2[0]=State[0]=0;
	
}


//-------------------------------------------------------------------------
// Function name 	: Aes_Encryption
// Purpose		: Compute a AES encryption . 
// Input: 
//	Plain is a pointer on an array containing the 16-byte data to encrypt.
//	W is a pointer on the array on 4*(Keylength+28) bytes containing the key schedule.
//	Keylength is the length of the Key. It can be equal to 16 bytes (128 bits), 24 bytes (192 bits) or 32 bytes (256 bits).
// Output: Cipher contains the 16-byte encrypted data.
///-------------------------------------------------------------------------
  void Aes_Encryption(unsigned char *  Cipher, unsigned char *  Plain, unsigned char *  W, unsigned char Keylength)
{
unsigned char Nbround,round;//,j;
unsigned char i;

SubKey=W;

Nbround = 4*(Keylength +24);

//AddRoundKey
for (i=15; i>0;i--) State[i]=Plain[i]^SubKey[i];
State[0]=Plain[0]^SubKey[0];

round=16;
do
	{
	Shiftrows_Subbyte();
	MixColumns();	
	//AddRoundKey	
	for (i=0; i<16;i++) State[i]^= SubKey[round++];
	} while (round<Nbround);
	
Shiftrows_Subbyte();
//AddRoundKey	
for (i=0; i<16;i++) Cipher[i]=State2[i]^ SubKey[round++];
// clear intermediate results (State, State2,SubKey) in page 0 	
Clear_AES_variables_page0();	
}	
	
	
//-------------------------------------------------------------------------
// Function name 	: Aes_Decryption
// Purpose		: Compute a AES Decryption . 
// Input: 
//	Cipher is a pointer on the array containing the 16-byte data to decrypt.
//	W is a pointer on the array on 4*(Keylength+28) bytes containing the key schedule.
//	Keylength is the length of the Key. It can be equal to 16 bytes (128 bits), 24 bytes (192 bits) or 32 bytes (256 bits).
// Output: Plain contains the 16-byte decrypted data.
///-------------------------------------------------------------------------

  void Aes_Decryption(unsigned char *  Plain, unsigned char *  Cipher, unsigned char *  W, unsigned char Keylength)
{
unsigned char i, round;
SubKey=W;
	
round = 4*(Keylength +28)-1;

//AddRoundKey
for (i=15; i>0;i--) State[i]=Cipher[i]^SubKey[round--];
State[0]=Cipher[0]^SubKey[round--];

do	{

 // compute State2 = InvShiftrow(InvSubbyte(State)) 
	Invshiftrows_Invsubbyte();	
	//AddRoundKey
	for (i=15; i>0;i--) State2[i]^=SubKey[round--];
	State2[0]^=SubKey[round--];

 //InvMixcolumn
	// Compute State = InvMixcolumn(State2)
	MixColumns();
	InvMixcolumn_end();

	} while (round>15);

// compute State2 = InvShiftrow(InvSubbyte(State)) 
Invshiftrows_Invsubbyte();	

//AddRoundKey
for (i=15; i>0;i--) Plain[i]=State2[i]^SubKey[i];
Plain[0]=State2[0]^SubKey[0];
// clear intermediate results (State, State2,SubKey) in page 0 	
Clear_AES_variables_page0();	
}

// -------------------------------------------------------------------------------
// void Clear_AES_variables_page0 (void)
//Clear State, State2 and  Subkey
// -------------------------------------------------------------------------------
void Clear_AES_variables_page0 (void)
{
unsigned char i;
SubKey=0;
for (i=15; i>0;i--) State2[i]=State[i]=0;
State2[0]=State[0]=0;

}	
// -------------------------------------------------------------------------------
/*Multiply for 2 a byte */
//if ((State2[index] & 0x80)!=0) {State2[index]= (State2[index] << 1) ^ 0x1b;}
//else State2[index]= (State2[index] << 1) ^0;
// -------------------------------------------------------------------------------

void xtime(unsigned char index)
{
   if ((State2[index] & 0x80)!=0) 
   {
   	   State2[index]= (State2[index] << 1) ^ 0x1b;
   }
   else 
   {	
   	   State2[index]= (State2[index] << 1) ^0;
   }	   
}

//-------------------------------------------------------------------------------
// compute State=InvMixcolumn_end(State) with State=MixColumns(State2)
// note:	s0'' = State[0]
//		s0' = State2[0]
//		s0 = Initial State2[0]