a3a8-opt.c

SOSSE,最简单的实现smart卡的教学用程序 内有电路图

/* $Id: a3a8-opt.c,v 1.1 2003/03/30 19:39:51 m Exp $ */

/* An implementation of the GSM A3A8 algorithm.  (Specifically, COMP128.) 
 */

/* Copyright 1998, Marc Briceno, Ian Goldberg, and David Wagner.
 * All rights reserved.
 */

/*
 * For expository purposes only.  Coded in C merely because C is a much
 * more precise, concise form of expression for these purposes.  See Judge
 * Patel if you have any problems with this...
 * Of course, it's only authentication, so it should be exportable for the
 * usual boring reasons.
 */

#include <string.h>
#include <types.h>

#ifdef TEST
#include <ctype.h>
#include <stdio.h>
#endif

/*
 * rand[0..15]: the challenge from the base station
 * key[0..15]: the SIM's A3/A8 long-term key Ki
 * simoutput[0..11]: what you'd get back if you fed rand and key to a real
 * SIM.
 *
 *   The GSM spec states that simoutput[0..3] is SRES,
 *   and simoutput[4..11] is Kc (the A5 session key).
 *   (See GSM 11.11, Section 8.16.  See also the leaked document
 *   referenced below.)
 *   Note that Kc is bits 74..127 of the COMP128 output, followed by 10
 *   zeros.
 *   In other words, A5 is keyed with only 54 bits of entropy. This
 *   represents a deliberate weakening of the key used for voice privacy
 *   by a factor of over 1000.
 * 
 * Verified with a Pacific Bell Schlumberger SIM.  Your mileage may vary.
 *
 * Marc Briceno <[e-mail]>, Ian Goldberg <[e-mail]>,
 * and David Wagner <[e-mail]>
 */

/* The compression tables. */
CODE static const iu8 tableidx[5] = {
	  0>>2,	/* Table 0 */
	512>>2,	/* Table 1 */
	768>>2,	/* Table 2 */
	896>>2,	/* Table 3 */
	960>>2	/* Table 4 */
};
CODE static const iu8 table[992] = {
	/* Table 0 */
	102,177,186,162,  2,156,112, 75, 55, 25,  8, 12,251,193,246,188,
	109,213,151, 53, 42, 79,191,115,233,242,164,223,209,148,108,161,
	252, 37,244, 47, 64,211,  6,237,185,160,139,113, 76,138, 59, 70,
	 67, 26, 13,157, 63,179,221, 30,214, 36,166, 69,152,124,207,116,
	247,194, 41, 84, 71,  1, 49, 14, 95, 35,169, 21, 96, 78,215,225,
	182,243, 28, 92,201,118,  4, 74,248,128, 17, 11,146,132,245, 48,
	149, 90,120, 39, 87,230,106,232,175, 19,126,190,202,141,137,176,
	250, 27,101, 40,219,227, 58, 20, 51,178, 98,216,140, 22, 32,121,
	 61,103,203, 72, 29,110, 85,212,180,204,150,183, 15, 66,172,196,
	 56,197,158,  0,100, 45,153,  7,144,222,163,167, 60,135,210,231,
	174,165, 38,249,224, 34,220,229,217,208,241, 68,206,189,125,255,
	239, 54,168, 89,123,122, 73,145,117,234,143, 99,129,200,192, 82,
	104,170,136,235, 93, 81,205,173,236, 94,105, 52, 46,228,198,  5,
	 57,254, 97,155,142,133,199,171,187, 50, 65,181,127,107,147,226,
	184,218,131, 33, 77, 86, 31, 44, 88, 62,238, 18, 24, 43,154, 23,
	 80,159,134,111,  9,114,  3, 91, 16,130, 83, 10,195,240,253,119,
	177,102,162,186,156,  2, 75,112, 25, 55, 12,  8,193,251,188,246,
	213,109, 53,151, 79, 42,115,191,242,233,223,164,148,209,161,108,
	 37,252, 47,244,211, 64,237,  6,160,185,113,139,138, 76, 70, 59,
	 26, 67,157, 13,179, 63, 30,221, 36,214, 69,166,124,152,116,207,
	194,247, 84, 41,  1, 71, 14, 49, 35, 95, 21,169, 78, 96,225,215,
	243,182, 92, 28,118,201, 74,  4,128,248, 11, 17,132,146, 48,245,
	 90,149, 39,120,230, 87,232,106, 19,175,190,126,141,202,176,137,
	 27,250, 40,101,227,219, 20, 58,178, 51,216, 98, 22,140,121, 32,
	103, 61, 72,203,110, 29,212, 85,204,180,183,150, 66, 15,196,172,
	197, 56,  0,158, 45,100,  7,153,222,144,167,163,135, 60,231,210,
	165,174,249, 38, 34,224,229,220,208,217, 68,241,189,206,255,125,
	 54,239, 89,168,122,123,145, 73,234,117, 99,143,200,129, 82,192,
	170,104,235,136, 81, 93,173,205, 94,236, 52,105,228, 46,  5,198,
	254, 57,155, 97,133,142,171,199, 50,187,181, 65,107,127,226,147,
	218,184, 33,131, 86, 77, 44, 31, 62, 88, 18,238, 43, 24, 23,154,
	159, 80,111,134,114,  9, 91,  3,130, 16, 10, 83,240,195,119,253,
	/* Table 1 */
	 19, 11, 80,114, 43,  1, 69, 94, 39, 18,127,117, 97,  3, 85, 43,
	 27,124, 70, 83, 47, 71, 63, 10, 47, 89, 79,  4, 14, 59, 11,  5,
	 35,107,103, 68, 21, 86, 36, 91, 85,126, 32, 50,109, 94,120,  6,
	 53, 79, 28, 45, 99, 95, 41, 34, 88, 68, 93, 55,110,125,105, 20,
	 90, 80, 76, 96, 23, 60, 89, 64,121, 56, 14, 74,101,  8, 19, 78,
	 76, 66,104, 46,111, 50, 32,  3, 39,  0, 58, 25, 92, 22, 18, 51,
	 57, 65,119,116, 22,109,  7, 86, 59, 93, 62,110, 78, 99, 77, 67,
	 12,113, 87, 98,102,  5, 88, 33, 38, 56, 23,  8, 75, 45, 13, 75,
	 95, 63, 28, 49,123,120, 20,112, 44, 30, 15, 98,106,  2,103, 29,
	 82,107, 42,124, 24, 30, 41, 16,108,100,117, 40, 73, 40,  7,114,
	 82,115, 36,112, 12,102,100, 84, 92, 48, 72, 97,  9, 54, 55, 74,
	113,123, 17, 26, 53, 58,  4,  9, 69,122, 21,118, 42, 60, 27, 73,
	118,125, 34, 15, 65,115, 84, 64, 62, 81, 70,  1, 24,111,121, 83,
	104, 81, 49,127, 48,105, 31, 10,  6, 91, 87, 37, 16, 54,116,126,
	 31, 38, 13,  0, 72,106, 77, 61, 26, 67, 46, 29, 96, 37, 61, 52,
	101, 17, 44,108, 71, 52, 66, 57, 33, 51, 25, 90,  2,119,122, 35,
	/* Table 2 */
	 52, 50, 44,  6, 21, 49, 41, 59, 39, 51, 25, 32, 51, 47, 52, 43,
	 37,  4, 40, 34, 61, 12, 28,  4, 58, 23,  8, 15, 12, 22,  9, 18,
	 55, 10, 33, 35, 50,  1, 43,  3, 57, 13, 62, 14,  7, 42, 44, 59,
	 62, 57, 27,  6,  8, 31, 26, 54, 41, 22, 45, 20, 39,  3, 16, 56,
	 48,  2, 21, 28, 36, 42, 60, 33, 34, 18,  0, 11, 24, 10, 17, 61,
	 29, 14, 45, 26, 55, 46, 11, 17, 54, 46,  9, 24, 30, 60, 32,  0,
	 20, 38,  2, 30, 58, 35,  1, 16, 56, 40, 23, 48, 13, 19, 19, 27,
	 31, 53, 47, 38, 63, 15, 49,  5, 37, 53, 25, 36, 63, 29,  5,  7,
	/* Table 3 */
	  1,  5, 29,  6, 25,  1, 18, 23, 17, 19,  0,  9, 24, 25,  6, 31,
	 28, 20, 24, 30,  4, 27,  3, 13, 15, 16, 14, 18,  4,  3,  8,  9,
	 20,  0, 12, 26, 21,  8, 28,  2, 29,  2, 15,  7, 11, 22, 14, 10,
	 17, 21, 12, 30, 26, 27, 16, 31, 11,  7, 13, 23, 10,  5, 22, 19,
	/* Table 4 */
	 15, 12, 10,  4,  1, 14, 11,  7,  5,  0, 14,  7,  1,  2, 13,  8,
	 10,  3,  4,  9,  6,  0,  3,  2,  5,  6,  8,  9, 11, 13, 15, 12
};

/*
 * This code derived from a leaked document from the GSM standards.
 * Some missing pieces were filled in by reverse-engineering a working SIM.
 * We have verified that this is the correct COMP128 algorithm.
 * 
 * The first page of the document identifies it as
 * 	_Technical Information: GSM System Security Study_.
 * 	10-1617-01, 10th June 1988.
 * The bottom of the title page is marked
 * 	Racal Research Ltd.
 * 	Worton Drive, Worton Grange Industrial Estate,
 * 	Reading, Berks. RG2 0SB, England.
 * 	Telephone: Reading [phone]   Telex: 847152
 * The relevant bits are in Part I, Section 20 (pages 66--67).  Enjoy!
 * 
 * Note: There are three typos in the spec (discovered by
 * reverse-engineering).
 * First, "z = (2 * x[n] + x[n]) mod 2^(9-j)" should clearly read
 * "z = (2 * x[m] + x[n]) mod 2^(9-j)".
 * Second, the "k" loop in the "Form bits from bytes" section is severely
 * botched: the k index should run only from 0 to 3, and clearly the range
 * on "the (8-k)th bit of byte j" is also off (should be 0..7, not 1..8,
 * to be consistent with the subsequent section).
 * Third, SRES is taken from the first 8 nibbles of x[], not the last 8 as
 * claimed in the document.  (And the document doesn't specify how Kc is
 * derived, but that was also easily discovered with reverse engineering.)
 * All of these typos have been corrected in the following code.
 */

static inline iu8 getbit( iu8 *array, iu8 pos )
{
	return ( (*( array + (pos>>3) )) >> (7-(pos&0x07)) ) & 0x01;
}

void A3A8( /* in */ iu8 key[16], /* in+out */ iu8 randout[16] )
{
	iu8 x[32];
	iu8 i, j, k, l, m, n;
	iu16 y, z;

	/* ( Load RAND into last 16 bytes of input ) */
	memcpy( x+16, randout, 16 );

	/* ( Loop eight times ) */
	for (i=1; i<9; i++) {
		/* ( Load key into first 16 bytes of input ) */
		memcpy( x, key, 16 );
		/* ( Perform substitutions ) */
		for (j=0; j<5; j++)
			for (k=0; k<(1<<j); k++)
				for (l=0; l<(1<<(4-j)); l++) {
					m = l + k*(1<<(5-j));
					n = m + (1<<(4-j));
					y = (x[m]+2*x[n]) % (1<<(9-j));
					z = (2*x[m]+x[n]) % (1<<(9-j));
					x[m] = PRG_RDB(table+(PRG_RDB(tableidx+j)<<2)+y);
					x[n] = PRG_RDB(table+(PRG_RDB(tableidx+j)<<2)+z);
				}
		/* ( Accumulate nipples for bit access ) */
		/* ( Usage of randout for bit array reduces RAM usage by 16 bytes
		 *   and increases Flash usage by 8 bytes. ) */
		memset( randout, 0, 16 );
		for (j=0; j<32; j++)
			randout[j>>1] |= x[j] << ( (j&1) ? 0 : 4 );
		/* ( Permutation but not on the last loop ) */
		if (i < 8) {
			memset( &x[16], 0, 16 );
			for (j=0; j<16; j++) {
				for (k=0; k<8; k++) {
					x[j+16] |= getbit( randout, ((8*j + k)*17) % 128 ) << (7-k);
				}
			}
		}
	}

	/*
	 * ( At this stage the vector x[] consists of 32 nibbles.
	 *   The first 8 of these are taken as the output SRES. )
	 */

	/* The remainder of the code is not given explicitly in the
	 * standard, but was derived by reverse-engineering.
	 */

	for (i=0; i<6; i++) {
		if( i<4 ) {
			randout[i] = (x[2*i]<<4) | x[2*i+1];
		}
		randout[4+i] = (x[2*i+18]<<6) | (x[2*i+18+1]<<2)
				| (x[2*i+18+2]>>2);
	}
	randout[4+6] = (x[2*6+18]<<6) | (x[2*6+18+1]<<2);
	randout[4+7] = 0;
}

#ifdef TEST
int hextoint(char x)
{
	x = toupper(x);
	if (x >= 'A' && x <= 'F')
		return x-'A'+10;
	else if (x >= '0' && x <= '9')
		return x-'0';
	fprintf(stderr, "bad input.\n");
	exit(1);
}

int main(int argc, char **argv)
{
	iu8 rand[16], key [16];
	int i;

	if (argc != 3 || strlen(argv[1]) != 34 || strlen(argv[2]) != 34
			|| strncmp(argv[1], "0x", 2) != 0
			|| strncmp(argv[2], "0x", 2) != 0) {
		fprintf(stderr, "Usage: %s 0x<key> 0x<rand>\n", argv[0]);
		exit(1);
	}

	for (i=0; i<16; i++)
		key[i] = (hextoint(argv[1][2*i+2])<<4)
			| hextoint(argv[1][2*i+3]);
	for (i=0; i<16; i++)
		rand[i] = (hextoint(argv[2][2*i+2])<<4)
			 | hextoint(argv[2][2*i+3]);
	A3A8(key, rand);
	printf("SRES + Kc: ");
	for (i=0; i<12; i++)
		printf("%02X", rand[i]);
	printf("\n");
	return 0;
}
#endif