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[crypto] Eliminate repetitions in MD5 round constant table

Signed-off-by: Michael Brown <mcb30@ipxe.org>
tags/v1.20.1
Michael Brown 7 years ago
parent
commit
32d54691e9
1 changed files with 10 additions and 7 deletions
  1. 10
    7
      src/crypto/md5.c

+ 10
- 7
src/crypto/md5.c View File

@@ -66,11 +66,11 @@ static const uint32_t k[64] = {
66 66
 };
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 /** MD5 shift amounts */
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-static const uint8_t r[64] = {
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-	7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
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-	5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20,
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-	4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
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-	6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21
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+static const uint8_t r[4][4] = {
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+	{  7, 12, 17, 22 },
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+	{  5,  9, 14, 20 },
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+	{  4, 11, 16, 23 },
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+	{  6, 10, 15, 21 },
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 };
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 /**
@@ -174,6 +174,7 @@ static void md5_digest ( struct md5_context *context ) {
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 	uint32_t g;
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 	uint32_t temp;
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 	struct md5_step *step;
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+	unsigned int round;
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 	unsigned int i;
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 	/* Sanity checks */
@@ -201,13 +202,15 @@ static void md5_digest ( struct md5_context *context ) {
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 	/* Main loop */
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 	for ( i = 0 ; i < 64 ; i++ ) {
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-		step = &md5_steps[ i / 16 ];
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+		round = ( i / 16 );
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+		step = &md5_steps[round];
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 		f = step->f ( &u.v );
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 		g = ( ( ( step->coefficient * i ) + step->constant ) % 16 );
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 		temp = *d;
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 		*d = *c;
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 		*c = *b;
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-		*b = ( *b + rol32 ( ( *a + f + k[i] + w[g] ), r[i] ) );
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+		*b = ( *b + rol32 ( ( *a + f + k[i] + w[g] ),
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+				    r[round][ i % 4 ] ) );
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 		*a = temp;
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 		DBGC2 ( context, "%2d : %08x %08x %08x %08x\n",
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 			i, *a, *b, *c, *d );

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