/*
 *	Optimized implementation of SKIPJACK algorithm
 *
 *	originally written by Panu Rissanen  1998.06.24
 *	optimized by Mark Tillotson  1998.06.25
 *	optimized by Paulo Barreto  1998.06.30
 *	gnupg support by Werner Koch  1998.07.02
 */

/* How to compile:
 *
   gcc -Wall -O2 -shared -fPIC -o skipjack skipjack.c
 */


#include 
#include 
#include 

/* configuration stuff */
#ifdef __alpha__
  #define SIZEOF_UNSIGNED_LONG 8
#else
  #define SIZEOF_UNSIGNED_LONG 4
#endif

#if defined(__mc68000__) || defined (__sparc__) || defined (__PPC__) \
    || (defined(__mips__) && (defined(MIPSEB) || defined (__MIPSEB__)) )
  #define BIG_ENDIAN_HOST 1
#else
  #define LITTLE_ENDIAN_HOST 1
#endif

typedef unsigned long  ulong;
typedef unsigned short ushort;
typedef unsigned char  byte;

typedef unsigned short u16;
#if SIZEOF_UNSIGNED_LONG == 4
  typedef unsigned long  u32;
  typedef unsigned long  word32;
#else
  typedef unsigned int	 u32;
  typedef unsigned int	 word32;
#endif

/* end configurable stuff */

#ifndef DIM
  #define DIM(v) (sizeof(v)/sizeof((v)[0]))
  #define DIMof(type,member)   DIM(((type *)0)->member)
#endif

/* imports */
void g10_log_fatal( const char *fmt, ... );


#define FNCCAST_SETKEY(f)  ((void(*)(void*, byte*, unsigned))(f))
#define FNCCAST_CRYPT(f)   ((void(*)(void*, byte*, byte*))(f))

typedef struct {
    byte tab[10][256];
} SJ_context;


static void selftest(void);

/**
 * The F-table byte permutation (see description of the G-box permutation)
 */
static const byte fTable[256] = {
	0xa3,0xd7,0x09,0x83,0xf8,0x48,0xf6,0xf4,0xb3,0x21,0x15,0x78,0x99,0xb1,0xaf,0xf9,
	0xe7,0x2d,0x4d,0x8a,0xce,0x4c,0xca,0x2e,0x52,0x95,0xd9,0x1e,0x4e,0x38,0x44,0x28,
	0x0a,0xdf,0x02,0xa0,0x17,0xf1,0x60,0x68,0x12,0xb7,0x7a,0xc3,0xe9,0xfa,0x3d,0x53,
	0x96,0x84,0x6b,0xba,0xf2,0x63,0x9a,0x19,0x7c,0xae,0xe5,0xf5,0xf7,0x16,0x6a,0xa2,
	0x39,0xb6,0x7b,0x0f,0xc1,0x93,0x81,0x1b,0xee,0xb4,0x1a,0xea,0xd0,0x91,0x2f,0xb8,
	0x55,0xb9,0xda,0x85,0x3f,0x41,0xbf,0xe0,0x5a,0x58,0x80,0x5f,0x66,0x0b,0xd8,0x90,
	0x35,0xd5,0xc0,0xa7,0x33,0x06,0x65,0x69,0x45,0x00,0x94,0x56,0x6d,0x98,0x9b,0x76,
	0x97,0xfc,0xb2,0xc2,0xb0,0xfe,0xdb,0x20,0xe1,0xeb,0xd6,0xe4,0xdd,0x47,0x4a,0x1d,
	0x42,0xed,0x9e,0x6e,0x49,0x3c,0xcd,0x43,0x27,0xd2,0x07,0xd4,0xde,0xc7,0x67,0x18,
	0x89,0xcb,0x30,0x1f,0x8d,0xc6,0x8f,0xaa,0xc8,0x74,0xdc,0xc9,0x5d,0x5c,0x31,0xa4,
	0x70,0x88,0x61,0x2c,0x9f,0x0d,0x2b,0x87,0x50,0x82,0x54,0x64,0x26,0x7d,0x03,0x40,
	0x34,0x4b,0x1c,0x73,0xd1,0xc4,0xfd,0x3b,0xcc,0xfb,0x7f,0xab,0xe6,0x3e,0x5b,0xa5,
	0xad,0x04,0x23,0x9c,0x14,0x51,0x22,0xf0,0x29,0x79,0x71,0x7e,0xff,0x8c,0x0e,0xe2,
	0x0c,0xef,0xbc,0x72,0x75,0x6f,0x37,0xa1,0xec,0xd3,0x8e,0x62,0x8b,0x86,0x10,0xe8,
	0x08,0x77,0x11,0xbe,0x92,0x4f,0x24,0xc5,0x32,0x36,0x9d,0xcf,0xf3,0xa6,0xbb,0xac,
	0x5e,0x6c,0xa9,0x13,0x57,0x25,0xb5,0xe3,0xbd,0xa8,0x3a,0x01,0x05,0x59,0x2a,0x46
};

/**
 * The key-dependent permutation G on V^16 is a four-round Feistel network.
 * The round function is a fixed byte-substitution table (permutation on V^8),
 * the F-table.  Each round of G incorporates a single byte from the key.
 */
#define g(tab, w, i, j, k, l) \
{ \
	w ^= (word32)tab[i][w & 0xff] << 8; \
	w ^= (word32)tab[j][w >>   8]; \
	w ^= (word32)tab[k][w & 0xff] << 8; \
	w ^= (word32)tab[l][w >>   8]; \
}

#define g0(tab, w) g(tab, w, 0, 1, 2, 3)
#define g1(tab, w) g(tab, w, 4, 5, 6, 7)
#define g2(tab, w) g(tab, w, 8, 9, 0, 1)
#define g3(tab, w) g(tab, w, 2, 3, 4, 5)
#define g4(tab, w) g(tab, w, 6, 7, 8, 9)

/**
 * The inverse of the G permutation.
 */
#define h(tab, w, i, j, k, l) \
{ \
	w ^= (word32)tab[l][w >>   8]; \
	w ^= (word32)tab[k][w & 0xff] << 8; \
	w ^= (word32)tab[j][w >>   8]; \
	w ^= (word32)tab[i][w & 0xff] << 8; \
}

#define h0(tab, w) h(tab, w, 0, 1, 2, 3)
#define h1(tab, w) h(tab, w, 4, 5, 6, 7)
#define h2(tab, w) h(tab, w, 8, 9, 0, 1)
#define h3(tab, w) h(tab, w, 2, 3, 4, 5)
#define h4(tab, w) h(tab, w, 6, 7, 8, 9)




/**
 * Preprocess a user key into a table to save an XOR at each F-table access.
 */
static void
makeKey( SJ_context *ctx, byte *key, unsigned keylen )
{
	int i;
	static int initialized;

	if( !initialized ) {
	    initialized = 1;
	    selftest();
	}

	assert(keylen == 10);
	/* tab[i][c] = fTable[c ^ key[i]] */
	for (i = 0; i < 10; i++) {
		byte *t = ctx->tab[i], k = key[i];
		int c;
		for (c = 0; c < 256; c++) {
			t[c] = fTable[c ^ k];
		}
	}
}

/**
 * Encrypt a single block of data.
 */
static void
encrypt_block( SJ_context *ctx, byte *out, byte *in )
{
	word32 w1, w2, w3, w4;

	w1 = (in[0] << 8) + in[1];
	w2 = (in[2] << 8) + in[3];
	w3 = (in[4] << 8) + in[5];
	w4 = (in[6] << 8) + in[7];

	/* stepping rule A: */
	g0((ctx->tab), w1); w4 ^= w1 ^ 1;
	g1((ctx->tab), w4); w3 ^= w4 ^ 2;
	g2((ctx->tab), w3); w2 ^= w3 ^ 3;
	g3((ctx->tab), w2); w1 ^= w2 ^ 4;
	g4((ctx->tab), w1); w4 ^= w1 ^ 5;
	g0((ctx->tab), w4); w3 ^= w4 ^ 6;
	g1((ctx->tab), w3); w2 ^= w3 ^ 7;
	g2((ctx->tab), w2); w1 ^= w2 ^ 8;

	/* stepping rule B: */
	w2 ^= w1 ^  9; g3((ctx->tab), w1);
	w1 ^= w4 ^ 10; g4((ctx->tab), w4);
	w4 ^= w3 ^ 11; g0((ctx->tab), w3);
	w3 ^= w2 ^ 12; g1((ctx->tab), w2);
	w2 ^= w1 ^ 13; g2((ctx->tab), w1);
	w1 ^= w4 ^ 14; g3((ctx->tab), w4);
	w4 ^= w3 ^ 15; g4((ctx->tab), w3);
	w3 ^= w2 ^ 16; g0((ctx->tab), w2);

	/* stepping rule A: */
	g1((ctx->tab), w1); w4 ^= w1 ^ 17;
	g2((ctx->tab), w4); w3 ^= w4 ^ 18;
	g3((ctx->tab), w3); w2 ^= w3 ^ 19;
	g4((ctx->tab), w2); w1 ^= w2 ^ 20;
	g0((ctx->tab), w1); w4 ^= w1 ^ 21;
	g1((ctx->tab), w4); w3 ^= w4 ^ 22;
	g2((ctx->tab), w3); w2 ^= w3 ^ 23;
	g3((ctx->tab), w2); w1 ^= w2 ^ 24;

	/* stepping rule B: */
	w2 ^= w1 ^ 25; g4((ctx->tab), w1);
	w1 ^= w4 ^ 26; g0((ctx->tab), w4);
	w4 ^= w3 ^ 27; g1((ctx->tab), w3);
	w3 ^= w2 ^ 28; g2((ctx->tab), w2);
	w2 ^= w1 ^ 29; g3((ctx->tab), w1);
	w1 ^= w4 ^ 30; g4((ctx->tab), w4);
	w4 ^= w3 ^ 31; g0((ctx->tab), w3);
	w3 ^= w2 ^ 32; g1((ctx->tab), w2);

	out[0] = (byte)(w1 >> 8); out[1] = (byte)w1;
	out[2] = (byte)(w2 >> 8); out[3] = (byte)w2;
	out[4] = (byte)(w3 >> 8); out[5] = (byte)w3;
	out[6] = (byte)(w4 >> 8); out[7] = (byte)w4;

}

/**
 * Decrypt a single block of data.
 */
static void
decrypt_block( SJ_context *ctx, byte *out, byte *in)
{
	word32 w1, w2, w3, w4;

	w1 = (in[0] << 8) + in[1];
	w2 = (in[2] << 8) + in[3];
	w3 = (in[4] << 8) + in[5];
	w4 = (in[6] << 8) + in[7];

	/* stepping rule A: */
	h1((ctx->tab), w2); w3 ^= w2 ^ 32;
	h0((ctx->tab), w3); w4 ^= w3 ^ 31;
	h4((ctx->tab), w4); w1 ^= w4 ^ 30;
	h3((ctx->tab), w1); w2 ^= w1 ^ 29;
	h2((ctx->tab), w2); w3 ^= w2 ^ 28;
	h1((ctx->tab), w3); w4 ^= w3 ^ 27;
	h0((ctx->tab), w4); w1 ^= w4 ^ 26;
	h4((ctx->tab), w1); w2 ^= w1 ^ 25;

	/* stepping rule B: */
	w1 ^= w2 ^ 24; h3((ctx->tab), w2);
	w2 ^= w3 ^ 23; h2((ctx->tab), w3);
	w3 ^= w4 ^ 22; h1((ctx->tab), w4);
	w4 ^= w1 ^ 21; h0((ctx->tab), w1);
	w1 ^= w2 ^ 20; h4((ctx->tab), w2);
	w2 ^= w3 ^ 19; h3((ctx->tab), w3);
	w3 ^= w4 ^ 18; h2((ctx->tab), w4);
	w4 ^= w1 ^ 17; h1((ctx->tab), w1);

	/* stepping rule A: */
	h0((ctx->tab), w2); w3 ^= w2 ^ 16;
	h4((ctx->tab), w3); w4 ^= w3 ^ 15;
	h3((ctx->tab), w4); w1 ^= w4 ^ 14;
	h2((ctx->tab), w1); w2 ^= w1 ^ 13;
	h1((ctx->tab), w2); w3 ^= w2 ^ 12;
	h0((ctx->tab), w3); w4 ^= w3 ^ 11;
	h4((ctx->tab), w4); w1 ^= w4 ^ 10;
	h3((ctx->tab), w1); w2 ^= w1 ^	9;

	/* stepping rule B: */
	w1 ^= w2 ^ 8; h2((ctx->tab), w2);
	w2 ^= w3 ^ 7; h1((ctx->tab), w3);
	w3 ^= w4 ^ 6; h0((ctx->tab), w4);
	w4 ^= w1 ^ 5; h4((ctx->tab), w1);
	w1 ^= w2 ^ 4; h3((ctx->tab), w2);
	w2 ^= w3 ^ 3; h2((ctx->tab), w3);
	w3 ^= w4 ^ 2; h1((ctx->tab), w4);
	w4 ^= w1 ^ 1; h0((ctx->tab), w1);

	out[0] = (byte)(w1 >> 8); out[1] = (byte)w1;
	out[2] = (byte)(w2 >> 8); out[3] = (byte)w2;
	out[4] = (byte)(w3 >> 8); out[5] = (byte)w3;
	out[6] = (byte)(w4 >> 8); out[7] = (byte)w4;

}

static void
selftest()
{
    SJ_context c;
    byte inp[8]     = { 0x33, 0x22, 0x11, 0x00, 0xdd, 0xcc, 0xbb, 0xaa };
    byte key[10]    = { 0x00, 0x99, 0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11 };
    byte enc[8], dec[8];
    byte chk[8]     = { 0x25, 0x87, 0xca, 0xe2, 0x7a, 0x12, 0xd3, 0x00 };

    makeKey( &c, key, 10 );
    encrypt_block( &c, enc, inp);
    if( memcmp( enc, chk, 8 ) )
	g10_log_fatal("Skipjack test encryption failed\n");
    decrypt_block( &c, dec, enc);
    if( memcmp( dec, inp, 8 ) )
	g10_log_fatal("Skipjack test decryption failed\n");
}


#ifdef TEST

#include 
#include 
#include 

int main() {
	byte inp[8]	= { 0x33, 0x22, 0x11, 0x00, 0xdd, 0xcc, 0xbb, 0xaa };
	byte key[10]	= { 0x00, 0x99, 0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11 };
	byte enc[8], dec[8];
	byte chk[8]	= { 0x25, 0x87, 0xca, 0xe2, 0x7a, 0x12, 0xd3, 0x00 };
	byte tab[10][256];
	int i;
	clock_t elapsed;

	makeKey(key, tab);
	encrypt(tab, inp, enc);
	printf((memcmp(enc, chk, 8) == 0) ? "encryption OK!\n" : "encryption failure!\n");
	decrypt(tab, enc, dec);
	printf((memcmp(dec, inp, 8) == 0) ? "decryption OK!\n" : "decryption failure!\n");

	elapsed = -clock();
	for (i = 0; i < 1000000; i++) {
		encrypt(tab, inp, enc);
	}
	elapsed += clock();
	printf ("elapsed time: %.1f s.\n", (float)elapsed/CLOCKS_PER_SEC);
	return 0;
}
#endif /*TEST*/


/****************
 * Return some information about the algorithm.  We need algo here to
 * distinguish different flavors of the algorithm.
 * Returns: A pointer to string describing the algorithm or NULL if
 *	    the ALGO is invalid.
 */
const char *
skipjack_get_info( int algo, size_t *keylen,
		   size_t *blocksize, size_t *contextsize,
		   void (**r_setkey)( void *c, byte *key, unsigned keylen ),
		   void (**r_encrypt)( void *c, byte *outbuf, byte *inbuf ),
		   void (**r_decrypt)( void *c, byte *outbuf, byte *inbuf )
		 )
{
    *keylen = 80;
    *blocksize = 8;
    *contextsize = sizeof(SJ_context);
    *r_setkey = FNCCAST_SETKEY(makeKey);
    *r_encrypt= FNCCAST_CRYPT(encrypt_block);
    *r_decrypt= FNCCAST_CRYPT(decrypt_block);
    if( algo == 101 )
	return "SKIPJACK";
    return NULL;
}



const char * const gnupgext_version = "Skipjack ($Revision: 1.1 $)";

static struct {
    int class;
    int version;
    int  value;
    void (*func)(void);
} func_table[] = {
    { 20, 1, 0, (void(*)(void))skipjack_get_info },
    { 21, 1, 101 },
};


void *
gnupgext_enum_func( int what, int *sequence, int *class, int *vers )
{
    void *ret;
    int i = *sequence;

    do {
	if( i >= DIM(func_table) || i < 0 ) {
	    return NULL;
	}
	*class = func_table[i].class;
	*vers  = func_table[i].version;
	switch( *class ) {
	  case 11:
	  case 21:
	  case 31:
	    ret = &func_table[i].value;
	    break;
	  default:
	    ret = func_table[i].func;
	    break;
	}
	i++;
    } while( what && what != *class );

    *sequence = i;
    return ret;
}