來自網絡上的SHA－1算法，自己加了少量注釋，方便以后需要的時候可以利用。

代碼：

/* sha1sum.c - print SHA-1 Message-Digest Algorithm
?* Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
?* Copyright (C) 2004 g10 Code GmbH
?*
?* This program is free software; you can redistribute it and/or modify it
?* under the terms of the GNU General Public License as published by the
?* Free Software Foundation; either version 2, or (at your option) any
?* later version.
?*
?* This program is distributed in the hope that it will be useful,
?* but WITHOUT ANY WARRANTY; without even the implied warranty of
?* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.? See the
?* GNU General Public License for more details.
?*
?* You should have received a copy of the GNU General Public License
?* along with this program; if not, write to the Free Software Foundation,
?* Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
?*/

/* SHA-1 coden take from gnupg 1.3.92.

?? Note, that this is a simple tool to be used for MS Windows.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>

#undef BIG_ENDIAN_HOST
typedef unsigned int u32;

/****************
?* Rotate a 32 bit integer by n bytes
?****************/
#if defined(__GNUC__) && defined(__i386__)
static inline u32 rol( u32 x, int n)
{
?__asm__("roll %%cl,%0"
??????????? :"=r" (x)
??????????? :"0" (x),"c" (n));
?return x;
}
#else
#define rol(x,n) ( ((x) << (n)) | ((x) >> (32-(n))) )
#endif

typedef struct {
??? u32? h0,h1,h2,h3,h4;???//哈希計算后的結果是20個bit，剛好相當于5個unsigned int(4字節)類型的數據
??? u32? nblocks;
??? unsigned char buf[64];
??? int? count;
} SHA1_CONTEXT;

?

void sha1_init( SHA1_CONTEXT *hd )?//計算前進行初始化
{
??? hd->h0 = 0x67452301;
??? hd->h1 = 0xefcdab89;
??? hd->h2 = 0x98badcfe;
??? hd->h3 = 0x10325476;
??? hd->h4 = 0xc3d2e1f0;
??? hd->nblocks = 0;
??? hd->count = 0;
}

/*
?* Transform the message X which consists of 16 32-bit-words
?*/
static void
transform( SHA1_CONTEXT *hd, unsigned char *data )
{
??? u32 a,b,c,d,e,tm;
??? u32 x[16];

??? /* get values from the chaining vars */
??? a = hd->h0;
??? b = hd->h1;
??? c = hd->h2;
??? d = hd->h3;
??? e = hd->h4;

#ifdef BIG_ENDIAN_HOST
??? memcpy( x, data, 64 );
#else
??? { int i;
??????? unsigned char *p2;
??????? for(i=0, p2=(unsigned char*)x; i < 16; i++, p2 += 4 ) {
??????????? p2[3] = *data++;
??????????? p2[2] = *data++;
??????????? p2[1] = *data++;
??????????? p2[0] = *data++;
??????? }
??? }
#endif

#define K1? 0x5A827999L
#define K2? 0x6ED9EBA1L
#define K3? 0x8F1BBCDCL
#define K4? 0xCA62C1D6L
#define F1(x,y,z)?? ( z ^ ( x & ( y ^ z ) ) )
#define F2(x,y,z)?? ( x ^ y ^ z )
#define F3(x,y,z)?? ( ( x & y ) | ( z & ( x | y ) ) )
#define F4(x,y,z)?? ( x ^ y ^ z )

#define M(i) ( tm =?? x[i&0x0f] ^ x[(i-14)&0x0f]??? /
?????????????? ^ x[(i-8)&0x0f] ^ x[(i-3)&0x0f]????? /
?????????????? , (x[i&0x0f] = rol(tm,1)) )

#define R(a,b,c,d,e,f,k,m)? do { e += rol( a, 5 )?? /
??????????? + f( b, c, d )????????????????????????? /
??????????? + k???????????????????????????????????? /
??????????? + m;??????????????????????????????????? /
??????? b = rol( b, 30 );?????????????????????????? /
??? } while(0)
??? R( a, b, c, d, e, F1, K1, x[ 0] );
??? R( e, a, b, c, d, F1, K1, x[ 1] );
??? R( d, e, a, b, c, F1, K1, x[ 2] );
??? R( c, d, e, a, b, F1, K1, x[ 3] );
??? R( b, c, d, e, a, F1, K1, x[ 4] );
??? R( a, b, c, d, e, F1, K1, x[ 5] );
??? R( e, a, b, c, d, F1, K1, x[ 6] );
??? R( d, e, a, b, c, F1, K1, x[ 7] );
??? R( c, d, e, a, b, F1, K1, x[ 8] );
??? R( b, c, d, e, a, F1, K1, x[ 9] );
??? R( a, b, c, d, e, F1, K1, x[10] );
??? R( e, a, b, c, d, F1, K1, x[11] );
??? R( d, e, a, b, c, F1, K1, x[12] );
??? R( c, d, e, a, b, F1, K1, x[13] );
??? R( b, c, d, e, a, F1, K1, x[14] );
??? R( a, b, c, d, e, F1, K1, x[15] );
??? R( e, a, b, c, d, F1, K1, M(16) );
??? R( d, e, a, b, c, F1, K1, M(17) );
??? R( c, d, e, a, b, F1, K1, M(18) );
??? R( b, c, d, e, a, F1, K1, M(19) );
??? R( a, b, c, d, e, F2, K2, M(20) );
??? R( e, a, b, c, d, F2, K2, M(21) );
??? R( d, e, a, b, c, F2, K2, M(22) );
??? R( c, d, e, a, b, F2, K2, M(23) );
??? R( b, c, d, e, a, F2, K2, M(24) );
??? R( a, b, c, d, e, F2, K2, M(25) );
??? R( e, a, b, c, d, F2, K2, M(26) );
??? R( d, e, a, b, c, F2, K2, M(27) );
??? R( c, d, e, a, b, F2, K2, M(28) );
??? R( b, c, d, e, a, F2, K2, M(29) );
??? R( a, b, c, d, e, F2, K2, M(30) );
??? R( e, a, b, c, d, F2, K2, M(31) );
??? R( d, e, a, b, c, F2, K2, M(32) );
??? R( c, d, e, a, b, F2, K2, M(33) );
??? R( b, c, d, e, a, F2, K2, M(34) );
??? R( a, b, c, d, e, F2, K2, M(35) );
??? R( e, a, b, c, d, F2, K2, M(36) );
??? R( d, e, a, b, c, F2, K2, M(37) );
??? R( c, d, e, a, b, F2, K2, M(38) );
??? R( b, c, d, e, a, F2, K2, M(39) );
??? R( a, b, c, d, e, F3, K3, M(40) );
??? R( e, a, b, c, d, F3, K3, M(41) );
??? R( d, e, a, b, c, F3, K3, M(42) );
??? R( c, d, e, a, b, F3, K3, M(43) );
??? R( b, c, d, e, a, F3, K3, M(44) );
??? R( a, b, c, d, e, F3, K3, M(45) );
??? R( e, a, b, c, d, F3, K3, M(46) );
??? R( d, e, a, b, c, F3, K3, M(47) );
??? R( c, d, e, a, b, F3, K3, M(48) );
??? R( b, c, d, e, a, F3, K3, M(49) );
??? R( a, b, c, d, e, F3, K3, M(50) );
??? R( e, a, b, c, d, F3, K3, M(51) );
??? R( d, e, a, b, c, F3, K3, M(52) );
??? R( c, d, e, a, b, F3, K3, M(53) );
??? R( b, c, d, e, a, F3, K3, M(54) );
??? R( a, b, c, d, e, F3, K3, M(55) );
??? R( e, a, b, c, d, F3, K3, M(56) );
??? R( d, e, a, b, c, F3, K3, M(57) );
??? R( c, d, e, a, b, F3, K3, M(58) );
??? R( b, c, d, e, a, F3, K3, M(59) );
??? R( a, b, c, d, e, F4, K4, M(60) );
??? R( e, a, b, c, d, F4, K4, M(61) );
??? R( d, e, a, b, c, F4, K4, M(62) );
??? R( c, d, e, a, b, F4, K4, M(63) );
??? R( b, c, d, e, a, F4, K4, M(64) );
??? R( a, b, c, d, e, F4, K4, M(65) );
??? R( e, a, b, c, d, F4, K4, M(66) );
??? R( d, e, a, b, c, F4, K4, M(67) );
??? R( c, d, e, a, b, F4, K4, M(68) );
??? R( b, c, d, e, a, F4, K4, M(69) );
??? R( a, b, c, d, e, F4, K4, M(70) );
??? R( e, a, b, c, d, F4, K4, M(71) );
??? R( d, e, a, b, c, F4, K4, M(72) );
??? R( c, d, e, a, b, F4, K4, M(73) );
??? R( b, c, d, e, a, F4, K4, M(74) );
??? R( a, b, c, d, e, F4, K4, M(75) );
??? R( e, a, b, c, d, F4, K4, M(76) );
??? R( d, e, a, b, c, F4, K4, M(77) );
??? R( c, d, e, a, b, F4, K4, M(78) );
??? R( b, c, d, e, a, F4, K4, M(79) );

??? /* Update chaining vars */
??? hd->h0 += a;
??? hd->h1 += b;
??? hd->h2 += c;
??? hd->h3 += d;
??? hd->h4 += e;
}

/* Update the message digest with the contents
?* of INBUF with length INLEN.
?*/
static void sha1_write( SHA1_CONTEXT *hd, unsigned char *inbuf, size_t inlen)
{
??? if( hd->count == 64 ) { /* flush the buffer */
??????? transform( hd, hd->buf );
??????? hd->count = 0;
??????? hd->nblocks++;
??? }
??? if( !inbuf )
??????? return;
??? if( hd->count ) {
??????? for( ; inlen && hd->count < 64; inlen-- )
??????????? hd->buf[hd->count++] = *inbuf++;
??????? sha1_write( hd, NULL, 0 );
??????? if( !inlen )
??????????? return;
??? }

??? while( inlen >= 64 ) {
??????? transform( hd, inbuf );
??????? hd->count = 0;
??????? hd->nblocks++;
??????? inlen -= 64;
??????? inbuf += 64;
??? }
??? for( ; inlen && hd->count < 64; inlen-- )
??????? hd->buf[hd->count++] = *inbuf++;
}

/* The routine final terminates the computation and
?* returns the digest.
?* The handle is prepared for a new cycle, but adding bytes to the
?* handle will the destroy the returned buffer.
?* Returns: 20 bytes representing the digest.
?*/

static void sha1_final(SHA1_CONTEXT *hd)
{
??? u32 t, msb, lsb;
??? unsigned char *p;

??? sha1_write(hd, NULL, 0); /* flush */;

??? t = hd->nblocks;
??? /* multiply by 64 to make a byte count */
??? lsb = t << 6;
??? msb = t >> 26;
??? /* add the count */
??? t = lsb;
??? if( (lsb += hd->count) < t )
??????? msb++;
??? /* multiply by 8 to make a bit count */
??? t = lsb;
??? lsb <<= 3;
??? msb <<= 3;
??? msb |= t >> 29;

??? if( hd->count < 56 ) { /* enough room */
??????? hd->buf[hd->count++] = 0x80; /* pad */
??????? while( hd->count < 56 )
??????????? hd->buf[hd->count++] = 0;? /* pad */
??? }
??? else { /* need one extra block */
??????? hd->buf[hd->count++] = 0x80; /* pad character */
??????? while( hd->count < 64 )
??????????? hd->buf[hd->count++] = 0;
??????? sha1_write(hd, NULL, 0);? /* flush */;
??????? memset(hd->buf, 0, 56 ); /* fill next block with zeroes */
??? }
??? /* append the 64 bit count */
??? hd->buf[56] = msb >> 24;
??? hd->buf[57] = msb >> 16;
??? hd->buf[58] = msb >>? 8;
??? hd->buf[59] = msb??? ;
??? hd->buf[60] = lsb >> 24;
??? hd->buf[61] = lsb >> 16;
??? hd->buf[62] = lsb >>? 8;
??? hd->buf[63] = lsb??? ;
??? transform( hd, hd->buf );

??? p = hd->buf;
#ifdef BIG_ENDIAN_HOST
#define X(a) do { *(u32*)p = hd->h##a ; p += 4; } while(0)
#else /* little endian */
#define X(a) do { *p++ = hd->h##a >> 24; *p++ = hd->h##a >> 16; /
??????? *p++ = hd->h##a >> 8; *p++ = hd->h##a; } while(0)
#endif
??? X(0);
??? X(1);
??? X(2);
??? X(3);
??? X(4);
#undef X
}

//用法如：SHA1.exe c.txt cc.txt?????//對c.txt和cc.txt中的內容進行哈希計算
int main (int argc, char **argv)
{
??? assert (sizeof (u32) == 4);

??? if (argc < 2)
??? {
??????? fprintf (stderr, "usage: sha1sum filenames/n");
??????? exit (1);
??? }
??? for (argc--, argv++; argc; argv++, argc--)?//實現對多個文件批量簽名，循環一次簽名一個文件
??? {
??????? FILE *fp;
??????? char buffer[4096];
??????? size_t n;
??????? SHA1_CONTEXT ctx;
??????? int i;
?????
??????? fp = fopen (*argv, "rb");????//讀取二進制文件
??????? if (!fp)
??????? {
??????????? fprintf (stderr, "can't open `%s': %s/n", *argv, strerror (errno));
??????????? exit (1);
??????? }
??????? sha1_init (&ctx);
??????? while ( (n = fread (buffer, 1, sizeof buffer, fp)))?//從fp指向的文件中讀取數據到buffer中
??????????? sha1_write (&ctx, buffer, n);?????//將buffer中的數據寫入到ctx中
??????? if (ferror (fp))
??????? {
??????????? fprintf (stderr, "error reading `%s': %s/n", *argv,strerror (errno));
??????????? exit (1);
??????? }
??????? sha1_final (&ctx);??????//計算哈希值，并將結果存到ctx.buf[]中
??????? fclose (fp);
?????
??????? for (i=0; i < 20; i++)
??????????? printf ("%02x", ctx.buf[i]);??//輸出哈希結果：每個字符占兩位輸出，以前導0進行填充
??????? printf ("? %s/n", *argv);????//輸出當前被簽名的文件名
??? }
??? return 0;
}

/*
Local Variables:
compile-command: "cc -Wall -g -o sha1sum sha1sum.c"
End:
*/

?

運行結果：（注意文件路徑的是否正確）

C:/Documents and Settings/Administrator>sha1.exe c.txt cc.txt
87754cd9deec60134aebf2f4f80c42c4172287e5? c.txt
46c1589181e4b72599341153304f303aa57c5051? cc.txt

?

C:/Documents and Settings/Administrator>

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