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I'm hoping to optimise an implementation of SHA-1 for an 8-bit MCU (8051-based). The input data is only 8-bytes, so I wonder if something could be done to improve this macro:
#define S(x,n) ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)))
The issue I have is that when macro P calls S with S(b, 30), it takes around 60us to complete. Since there're 80 calls to P, it totals to around 4.8ms.
If I'm correct, S(x,n) expects x to be a uint32. Given the rather small input size, could the number of shifts be reduced by making x smaller, e.g., uint8?
If so, is this the only change needed? From:
#define S(x,n) ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)))
To:
#define S(x,n) ((x << n) | ((x & 0xFF) >> (8 - n)))
From:
void sha1_process( sha1_context *ctx, uint8 data[64] )
{
uint32 temp, W[16], A, B, C, D, E;
// ...
To:
void sha1_process( sha1_context *ctx, uint8 data[64] )
{
uint8 temp, W[16], A, B, C, D, E;
// ...
Here's the complete code:
#include <string.h>
#include "sha1.h"
#define GET_UINT32(n,b,i) \
{ \
(n) = ( (uint32) (b)[(i) ] << 24 ) \
| ( (uint32) (b)[(i) + 1] << 16 ) \
| ( (uint32) (b)[(i) + 2] << 8 ) \
| ( (uint32) (b)[(i) + 3] ); \
}
#define PUT_UINT32(n,b,i) \
{ \
(b)[(i) ] = (uint8) ( (n) >> 24 ); \
(b)[(i) + 1] = (uint8) ( (n) >> 16 ); \
(b)[(i) + 2] = (uint8) ( (n) >> 8 ); \
(b)[(i) + 3] = (uint8) ( (n) ); \
}
void sha1_starts( sha1_context *ctx )
{
ctx->total[0] = 0;
ctx->total[1] = 0;
ctx->state[0] = 0x67452301;
ctx->state[1] = 0xEFCDAB89;
ctx->state[2] = 0x98BADCFE;
ctx->state[3] = 0x10325476;
ctx->state[4] = 0xC3D2E1F0;
}
void sha1_process( sha1_context *ctx, uint8 data[64] )
{
uint32 temp, W[16], A, B, C, D, E;
GET_UINT32( W[0], data, 0 );
GET_UINT32( W[1], data, 4 );
GET_UINT32( W[2], data, 8 );
GET_UINT32( W[3], data, 12 );
GET_UINT32( W[4], data, 16 );
GET_UINT32( W[5], data, 20 );
GET_UINT32( W[6], data, 24 );
GET_UINT32( W[7], data, 28 );
GET_UINT32( W[8], data, 32 );
GET_UINT32( W[9], data, 36 );
GET_UINT32( W[10], data, 40 );
GET_UINT32( W[11], data, 44 );
GET_UINT32( W[12], data, 48 );
GET_UINT32( W[13], data, 52 );
GET_UINT32( W[14], data, 56 );
GET_UINT32( W[15], data, 60 );
#define S(x,n) ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)))
#define R(t) \
( \
temp = W[(t - 3) & 0x0F] ^ W[(t - 8) & 0x0F] ^ \
W[(t - 14) & 0x0F] ^ W[ t & 0x0F], \
( W[t & 0x0F] = S(temp,1) ) \
)
#define P(a,b,c,d,e,x) \
{ \
e += S(a,5) + F(b,c,d) + K + x; b = S(b,30); \
}
A = ctx->state[0];
B = ctx->state[1];
C = ctx->state[2];
D = ctx->state[3];
E = ctx->state[4];
#define F(x,y,z) (z ^ (x & (y ^ z)))
#define K 0x5A827999
P( A, B, C, D, E, W[0] );
P( E, A, B, C, D, W[1] );
P( D, E, A, B, C, W[2] );
P( C, D, E, A, B, W[3] );
P( B, C, D, E, A, W[4] );
P( A, B, C, D, E, W[5] );
P( E, A, B, C, D, W[6] );
P( D, E, A, B, C, W[7] );
P( C, D, E, A, B, W[8] );
P( B, C, D, E, A, W[9] );
P( A, B, C, D, E, W[10] );
P( E, A, B, C, D, W[11] );
P( D, E, A, B, C, W[12] );
P( C, D, E, A, B, W[13] );
P( B, C, D, E, A, W[14] );
P( A, B, C, D, E, W[15] );
P( E, A, B, C, D, R(16) );
P( D, E, A, B, C, R(17) );
P( C, D, E, A, B, R(18) );
P( B, C, D, E, A, R(19) );
#undef K
#undef F
#define F(x,y,z) (x ^ y ^ z)
#define K 0x6ED9EBA1
P( A, B, C, D, E, R(20) );
P( E, A, B, C, D, R(21) );
P( D, E, A, B, C, R(22) );
P( C, D, E, A, B, R(23) );
P( B, C, D, E, A, R(24) );
P( A, B, C, D, E, R(25) );
P( E, A, B, C, D, R(26) );
P( D, E, A, B, C, R(27) );
P( C, D, E, A, B, R(28) );
P( B, C, D, E, A, R(29) );
P( A, B, C, D, E, R(30) );
P( E, A, B, C, D, R(31) );
P( D, E, A, B, C, R(32) );
P( C, D, E, A, B, R(33) );
P( B, C, D, E, A, R(34) );
P( A, B, C, D, E, R(35) );
P( E, A, B, C, D, R(36) );
P( D, E, A, B, C, R(37) );
P( C, D, E, A, B, R(38) );
P( B, C, D, E, A, R(39) );
#undef K
#undef F
#define F(x,y,z) ((x & y) | (z & (x | y)))
#define K 0x8F1BBCDC
P( A, B, C, D, E, R(40) );
P( E, A, B, C, D, R(41) );
P( D, E, A, B, C, R(42) );
P( C, D, E, A, B, R(43) );
P( B, C, D, E, A, R(44) );
P( A, B, C, D, E, R(45) );
P( E, A, B, C, D, R(46) );
P( D, E, A, B, C, R(47) );
P( C, D, E, A, B, R(48) );
P( B, C, D, E, A, R(49) );
P( A, B, C, D, E, R(50) );
P( E, A, B, C, D, R(51) );
P( D, E, A, B, C, R(52) );
P( C, D, E, A, B, R(53) );
P( B, C, D, E, A, R(54) );
P( A, B, C, D, E, R(55) );
P( E, A, B, C, D, R(56) );
P( D, E, A, B, C, R(57) );
P( C, D, E, A, B, R(58) );
P( B, C, D, E, A, R(59) );
#undef K
#undef F
#define F(x,y,z) (x ^ y ^ z)
#define K 0xCA62C1D6
P( A, B, C, D, E, R(60) );
P( E, A, B, C, D, R(61) );
P( D, E, A, B, C, R(62) );
P( C, D, E, A, B, R(63) );
P( B, C, D, E, A, R(64) );
P( A, B, C, D, E, R(65) );
P( E, A, B, C, D, R(66) );
P( D, E, A, B, C, R(67) );
P( C, D, E, A, B, R(68) );
P( B, C, D, E, A, R(69) );
P( A, B, C, D, E, R(70) );
P( E, A, B, C, D, R(71) );
P( D, E, A, B, C, R(72) );
P( C, D, E, A, B, R(73) );
P( B, C, D, E, A, R(74) );
P( A, B, C, D, E, R(75) );
P( E, A, B, C, D, R(76) );
P( D, E, A, B, C, R(77) );
P( C, D, E, A, B, R(78) );
P( B, C, D, E, A, R(79) );
#undef K
#undef F
ctx->state[0] += A;
ctx->state[1] += B;
ctx->state[2] += C;
ctx->state[3] += D;
ctx->state[4] += E;
}
void sha1_update( sha1_context *ctx, uint8 *input, uint32 length )
{
uint32 left, fill;
if( ! length ) return;
left = ctx->total[0] & 0x3F;
fill = 64 - left;
ctx->total[0] += length;
ctx->total[0] &= 0xFFFFFFFF;
if( ctx->total[0] < length )
ctx->total[1]++;
if( left && length >= fill )
{
memcpy( (void *) (ctx->buffer + left),
(void *) input, fill );
sha1_process( ctx, ctx->buffer );
length -= fill;
input += fill;
left = 0;
}
while( length >= 64 )
{
sha1_process( ctx, input );
length -= 64;
input += 64;
}
if( length )
{
memcpy( (void *) (ctx->buffer + left),
(void *) input, length );
}
}
static uint8 sha1_padding[64] =
{
0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
void sha1_finish( sha1_context *ctx, uint8 digest[20] )
{
uint32 last, padn;
uint32 high, low;
uint8 msglen[8];
high = ( ctx->total[0] >> 29 )
| ( ctx->total[1] << 3 );
low = ( ctx->total[0] << 3 );
PUT_UINT32( high, msglen, 0 );
PUT_UINT32( low, msglen, 4 );
last = ctx->total[0] & 0x3F;
padn = ( last < 56 ) ? ( 56 - last ) : ( 120 - last );
sha1_update( ctx, sha1_padding, padn );
sha1_update( ctx, msglen, 8 );
PUT_UINT32( ctx->state[0], digest, 0 );
PUT_UINT32( ctx->state[1], digest, 4 );
PUT_UINT32( ctx->state[2], digest, 8 );
PUT_UINT32( ctx->state[3], digest, 12 );
PUT_UINT32( ctx->state[4], digest, 16 );
}
#ifdef TEST
#include <stdlib.h>
#include <stdio.h>
/*
* those are the standard FIPS-180-1 test vectors
*/
static char *msg[] =
{
"abc",
"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
NULL
};
static char *val[] =
{
"a9993e364706816aba3e25717850c26c9cd0d89d",
"84983e441c3bd26ebaae4aa1f95129e5e54670f1",
"34aa973cd4c4daa4f61eeb2bdbad27316534016f"
};
int main( int argc, char *argv[] )
{
FILE *f;
int i, j;
char output[41];
sha1_context ctx;
unsigned char buf[1000];
unsigned char sha1sum[20];
if( argc < 2 )
{
printf( "\n SHA-1 Validation Tests:\n\n" );
for( i = 0; i < 3; i++ )
{
printf( " Test %d ", i + 1 );
sha1_starts( &ctx );
if( i < 2 )
{
sha1_update( &ctx, (uint8 *) msg[i],
strlen( msg[i] ) );
}
else
{
memset( buf, 'a', 1000 );
for( j = 0; j < 1000; j++ )
{
sha1_update( &ctx, (uint8 *) buf, 1000 );
}
}
sha1_finish( &ctx, sha1sum );
for( j = 0; j < 20; j++ )
{
sprintf( output + j * 2, "%02x", sha1sum[j] );
}
if( memcmp( output, val[i], 40 ) )
{
printf( "failed!\n" );
return( 1 );
}
printf( "passed.\n" );
}
printf( "\n" );
}
else
{
if( ! ( f = fopen( argv[1], "rb" ) ) )
{
perror( "fopen" );
return( 1 );
}
sha1_starts( &ctx );
while( ( i = fread( buf, 1, sizeof( buf ), f ) ) > 0 )
{
sha1_update( &ctx, buf, i );
}
sha1_finish( &ctx, sha1sum );
for( j = 0; j < 20; j++ )
{
printf( "%02x", sha1sum[j] );
}
printf( " %s\n", argv[1] );
}
return( 0 );
}
#endif
Here's an example of the generated code for S(x,n) when called by P( E, A, B, C, D, W[1] ):
0031D0 85 18 82 MOV DPL,XSP(L)
0031D3 85 19 83 MOV DPH,XSP(H)
0031D6 78 08 MOV R0,#0x08
0031D8 12 17 85 LCALL ?L_MOV_X
0031DB 74 1E MOV A,#0x1E
0031DD 78 08 MOV R0,#0x08
0031DF 12 16 80 LCALL ?L_SHL
0031E2 85 18 82 MOV DPL,XSP(L)
0031E5 85 19 83 MOV DPH,XSP(H)
0031E8 78 10 MOV R0,#0x10
0031EA 12 17 85 LCALL ?L_MOV_X
0031ED 74 02 MOV A,#0x02
0031EF 78 10 MOV R0,#0x10
0031F1 12 16 67 LCALL ?UL_SHR
0031F4 78 08 MOV R0,#0x08
0031F6 79 10 MOV R1,#0x10
0031F8 12 17 39 LCALL ?L_IOR
0031FB 85 18 82 MOV DPL,XSP(L)
0031FE 85 19 83 MOV DPH,XSP(H)
003201 78 08 MOV R0,#0x08
003203 12 17 94 LCALL ?L_MOV_TO_X
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