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-rw-r--r--aes.c78
1 files changed, 46 insertions, 32 deletions
diff --git a/aes.c b/aes.c
index daa9f6f..967f184 100644
--- a/aes.c
+++ b/aes.c
@@ -18,10 +18,10 @@ ECB-AES128
2b7e151628aed2a6abf7158809cf4f3c
resulting cipher
- 50fe67cc996d32b6da0937e99bafec60
- d9a4dada0892239f6b8b3d7680e15674
- a78819583f0308e7a6bf36b1386abf23
- c6d3416d29165c6fcb8e51a227ba994e
+ 3ad77bb40d7a3660a89ecaf32466ef97
+ f5d3d58503b9699de785895a96fdbaaf
+ 43b1cd7f598ece23881b00e3ed030688
+ 7b0c785e27e8ad3f8223207104725dd4
NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0)
@@ -29,9 +29,6 @@ NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0)
*/
-#ifndef _AES_C_
-#define _AES_C_
-
/*****************************************************************************/
/* Includes: */
@@ -52,6 +49,10 @@ NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0)
// The number of rounds in AES Cipher.
#define Nr 10
+// jcallan@github points out that declaring Multiply as a function
+// reduces code size considerably with the Keil ARM compiler.
+// See this link for more information: https://github.com/kokke/tiny-AES128-C/pull/3
+#define MULTIPLY_AS_A_FUNCTION 0
/*****************************************************************************/
/* Private variables: */
@@ -143,9 +144,8 @@ static uint8_t getSBoxInvert(uint8_t num)
return rsbox[num];
}
-
// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
-static void KeyExpansion()
+static void KeyExpansion(void)
{
uint32_t i, j, k;
uint8_t tempa[4]; // Used for the column/row operations
@@ -212,10 +212,10 @@ static void KeyExpansion()
// This function adds the round key to state.
// The round key is added to the state by an XOR function.
-static void AddRoundKey(uint8_t round)
+static void AddRoundKey(uint8_t round)
{
uint8_t i,j;
- for(i=0;i<4;i++)
+ for(i=0;i<4;++i)
{
for(j = 0; j < 4; ++j)
{
@@ -226,7 +226,7 @@ static void AddRoundKey(uint8_t round)
// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
-static void SubBytes()
+static void SubBytes(void)
{
uint8_t i, j;
for(i = 0; i < 4; ++i)
@@ -241,7 +241,7 @@ static void SubBytes()
// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
-static void ShiftRows()
+static void ShiftRows(void)
{
uint8_t temp;
@@ -275,7 +275,7 @@ static uint8_t xtime(uint8_t x)
}
// MixColumns function mixes the columns of the state matrix
-static void MixColumns()
+static void MixColumns(void)
{
uint8_t i;
uint8_t Tmp,Tm,t;
@@ -290,18 +290,36 @@ static void MixColumns()
}
}
-// Multiplty is a macro used to multiply numbers in the field GF(2^8)
-#define Multiply(x,y) (((y & 1) * x) ^ ((y>>1 & 1) * xtime(x)) ^ ((y>>2 & 1) * xtime(xtime(x))) ^ ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))))
+// Multiply is used to multiply numbers in the field GF(2^8)
+#if MULTIPLY_AS_A_FUNCTION
+static uint8_t Multiply(uint8_t x, uint8_t y)
+{
+ return (((y & 1) * x) ^
+ ((y>>1 & 1) * xtime(x)) ^
+ ((y>>2 & 1) * xtime(xtime(x))) ^
+ ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^
+ ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))));
+ }
+#else
+#define Multiply(x, y) \
+ ( ((y & 1) * x) ^ \
+ ((y>>1 & 1) * xtime(x)) ^ \
+ ((y>>2 & 1) * xtime(xtime(x))) ^ \
+ ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ \
+ ((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))) \
+
+#endif
+
// MixColumns function mixes the columns of the state matrix.
// The method used to multiply may be difficult to understand for the inexperienced.
// Please use the references to gain more information.
-static void InvMixColumns()
+static void InvMixColumns(void)
{
int i;
uint8_t a,b,c,d;
- for(i=0;i<4;i++)
+ for(i=0;i<4;++i)
{
a = state[0][i];
@@ -320,20 +338,19 @@ static void InvMixColumns()
// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
-static void InvSubBytes()
+static void InvSubBytes(void)
{
uint8_t i,j;
- for(i=0;i<4;i++)
+ for(i=0;i<4;++i)
{
- for(j=0;j<4;j++)
+ for(j=0;j<4;++j)
{
state[i][j] = getSBoxInvert(state[i][j]);
}
}
}
-
-static void InvShiftRows()
+static void InvShiftRows(void)
{
uint8_t temp;
@@ -363,7 +380,7 @@ static void InvShiftRows()
// Cipher is the main function that encrypts the PlainText.
-static void Cipher()
+static void Cipher(void)
{
uint8_t i, j, round = 0;
@@ -407,14 +424,14 @@ static void Cipher()
}
}
-static void InvCipher()
+static void InvCipher(void)
{
uint8_t i,j,round=0;
// Copy the input CipherText to state array.
- for(i=0;i<4;i++)
+ for(i=0;i<4;++i)
{
- for(j=0;j<4;j++)
+ for(j=0;j<4;++j)
{
state[j][i] = in[i*4 + j];
}
@@ -442,9 +459,9 @@ static void InvCipher()
// The decryption process is over.
// Copy the state array to output array.
- for(i=0;i<4;i++)
+ for(i=0;i<4;++i)
{
- for(j=0;j<4;j++)
+ for(j=0;j<4;++j)
{
out[i*4+j]=state[j][i];
}
@@ -481,6 +498,3 @@ void AES128_ECB_decrypt(uint8_t* input, uint8_t* key, uint8_t *output)
InvCipher();
}
-#endif //_AES_C_
-
-