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394 lines
7.1 KiB
C++
394 lines
7.1 KiB
C++
// Purpose: C++ implementation of the ICE encryption algorithm.
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// Taken from public domain code, as written by Matthew Kwan - July 1996
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// http://www.darkside.com.au/ice/
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#if !defined(_STATIC_LINKED) || defined(_SHARED_LIB)
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#include "mathlib/IceKey.H"
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#include "tier0/memdbgon.h"
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#pragma warning(disable: 4244)
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/* Structure of a single round subkey */
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class IceSubkey {
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public:
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unsigned long val[3];
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};
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/* The S-boxes */
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static unsigned long ice_sbox[4][1024];
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static int ice_sboxes_initialised = 0;
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/* Modulo values for the S-boxes */
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static const int ice_smod[4][4] = {
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{333, 313, 505, 369},
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{379, 375, 319, 391},
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{361, 445, 451, 397},
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{397, 425, 395, 505}};
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/* XOR values for the S-boxes */
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static const int ice_sxor[4][4] = {
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{0x83, 0x85, 0x9b, 0xcd},
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{0xcc, 0xa7, 0xad, 0x41},
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{0x4b, 0x2e, 0xd4, 0x33},
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{0xea, 0xcb, 0x2e, 0x04}};
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/* Permutation values for the P-box */
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static const unsigned long ice_pbox[32] = {
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0x00000001, 0x00000080, 0x00000400, 0x00002000,
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0x00080000, 0x00200000, 0x01000000, 0x40000000,
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0x00000008, 0x00000020, 0x00000100, 0x00004000,
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0x00010000, 0x00800000, 0x04000000, 0x20000000,
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0x00000004, 0x00000010, 0x00000200, 0x00008000,
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0x00020000, 0x00400000, 0x08000000, 0x10000000,
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0x00000002, 0x00000040, 0x00000800, 0x00001000,
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0x00040000, 0x00100000, 0x02000000, 0x80000000};
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/* The key rotation schedule */
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static const int ice_keyrot[16] = {
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0, 1, 2, 3, 2, 1, 3, 0,
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1, 3, 2, 0, 3, 1, 0, 2};
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/*
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* 8-bit Galois Field multiplication of a by b, modulo m.
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* Just like arithmetic multiplication, except that additions and
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* subtractions are replaced by XOR.
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*/
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static unsigned int
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gf_mult (
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unsigned int a,
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unsigned int b,
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unsigned int m
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) {
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unsigned int res = 0;
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while (b) {
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if (b & 1)
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res ^= a;
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a <<= 1;
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b >>= 1;
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if (a >= 256)
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a ^= m;
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}
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return (res);
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}
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/*
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* Galois Field exponentiation.
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* Raise the base to the power of 7, modulo m.
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*/
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static unsigned long
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gf_exp7 (
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unsigned int b,
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unsigned int m
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) {
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unsigned int x;
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if (b == 0)
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return (0);
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x = gf_mult (b, b, m);
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x = gf_mult (b, x, m);
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x = gf_mult (x, x, m);
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return (gf_mult (b, x, m));
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}
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/*
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* Carry out the ICE 32-bit P-box permutation.
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*/
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static unsigned long
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ice_perm32 (
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unsigned long x
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) {
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unsigned long res = 0;
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const unsigned long *pbox = ice_pbox;
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while (x) {
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if (x & 1)
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res |= *pbox;
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pbox++;
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x >>= 1;
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}
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return (res);
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}
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/*
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* Initialise the ICE S-boxes.
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* This only has to be done once.
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*/
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static void
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ice_sboxes_init (void)
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{
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int i;
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for (i=0; i<1024; i++) {
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int col = (i >> 1) & 0xff;
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int row = (i & 0x1) | ((i & 0x200) >> 8);
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unsigned long x;
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x = gf_exp7 (col ^ ice_sxor[0][row], ice_smod[0][row]) << 24;
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ice_sbox[0][i] = ice_perm32 (x);
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x = gf_exp7 (col ^ ice_sxor[1][row], ice_smod[1][row]) << 16;
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ice_sbox[1][i] = ice_perm32 (x);
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x = gf_exp7 (col ^ ice_sxor[2][row], ice_smod[2][row]) << 8;
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ice_sbox[2][i] = ice_perm32 (x);
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x = gf_exp7 (col ^ ice_sxor[3][row], ice_smod[3][row]);
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ice_sbox[3][i] = ice_perm32 (x);
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}
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}
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/*
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* Create a new ICE key.
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*/
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IceKey::IceKey (int n)
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{
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if (!ice_sboxes_initialised) {
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ice_sboxes_init ();
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ice_sboxes_initialised = 1;
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}
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if (n < 1) {
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_size = 1;
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_rounds = 8;
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} else {
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_size = n;
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_rounds = n * 16;
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}
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_keysched = new IceSubkey[_rounds];
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}
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/*
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* Destroy an ICE key.
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*/
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IceKey::~IceKey ()
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{
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int i, j;
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for (i=0; i<_rounds; i++)
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for (j=0; j<3; j++)
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_keysched[i].val[j] = 0;
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_rounds = _size = 0;
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delete[] _keysched;
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}
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/*
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* The single round ICE f function.
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*/
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static unsigned long
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ice_f (
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unsigned long p,
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const IceSubkey *sk
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) {
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unsigned long tl, tr; /* Expanded 40-bit values */
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unsigned long al, ar; /* Salted expanded 40-bit values */
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/* Left half expansion */
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tl = ((p >> 16) & 0x3ff) | (((p >> 14) | (p << 18)) & 0xffc00);
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/* Right half expansion */
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tr = (p & 0x3ff) | ((p << 2) & 0xffc00);
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/* Perform the salt permutation */
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// al = (tr & sk->val[2]) | (tl & ~sk->val[2]);
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// ar = (tl & sk->val[2]) | (tr & ~sk->val[2]);
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al = sk->val[2] & (tl ^ tr);
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ar = al ^ tr;
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al ^= tl;
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al ^= sk->val[0]; /* XOR with the subkey */
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ar ^= sk->val[1];
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/* S-box lookup and permutation */
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return (ice_sbox[0][al >> 10] | ice_sbox[1][al & 0x3ff]
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| ice_sbox[2][ar >> 10] | ice_sbox[3][ar & 0x3ff]);
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}
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/*
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* Encrypt a block of 8 bytes of data with the given ICE key.
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*/
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void
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IceKey::encrypt (
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const unsigned char *ptext,
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unsigned char *ctext
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) const
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{
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int i;
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unsigned long l, r;
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l = (((unsigned long) ptext[0]) << 24)
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| (((unsigned long) ptext[1]) << 16)
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| (((unsigned long) ptext[2]) << 8) | ptext[3];
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r = (((unsigned long) ptext[4]) << 24)
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| (((unsigned long) ptext[5]) << 16)
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| (((unsigned long) ptext[6]) << 8) | ptext[7];
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for (i = 0; i < _rounds; i += 2) {
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l ^= ice_f (r, &_keysched[i]);
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r ^= ice_f (l, &_keysched[i + 1]);
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}
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for (i = 0; i < 4; i++) {
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ctext[3 - i] = r & 0xff;
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ctext[7 - i] = l & 0xff;
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r >>= 8;
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l >>= 8;
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}
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}
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/*
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* Decrypt a block of 8 bytes of data with the given ICE key.
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*/
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void
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IceKey::decrypt (
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const unsigned char *ctext,
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unsigned char *ptext
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) const
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{
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int i;
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unsigned long l, r;
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l = (((unsigned long) ctext[0]) << 24)
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| (((unsigned long) ctext[1]) << 16)
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| (((unsigned long) ctext[2]) << 8) | ctext[3];
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r = (((unsigned long) ctext[4]) << 24)
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| (((unsigned long) ctext[5]) << 16)
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| (((unsigned long) ctext[6]) << 8) | ctext[7];
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for (i = _rounds - 1; i > 0; i -= 2) {
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l ^= ice_f (r, &_keysched[i]);
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r ^= ice_f (l, &_keysched[i - 1]);
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}
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for (i = 0; i < 4; i++) {
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ptext[3 - i] = r & 0xff;
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ptext[7 - i] = l & 0xff;
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r >>= 8;
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l >>= 8;
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}
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}
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/*
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* Set 8 rounds [n, n+7] of the key schedule of an ICE key.
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*/
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void
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IceKey::scheduleBuild (
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unsigned short *kb,
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int n,
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const int *keyrot
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) {
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int i;
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for (i=0; i<8; i++) {
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int j;
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int kr = keyrot[i];
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IceSubkey *isk = &_keysched[n + i];
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for (j=0; j<3; j++)
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isk->val[j] = 0;
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for (j=0; j<15; j++) {
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int k;
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unsigned long *curr_sk = &isk->val[j % 3];
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for (k=0; k<4; k++) {
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unsigned short *curr_kb = &kb[(kr + k) & 3];
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int bit = *curr_kb & 1;
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*curr_sk = (*curr_sk << 1) | bit;
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*curr_kb = (*curr_kb >> 1) | ((bit ^ 1) << 15);
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}
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}
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}
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}
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/*
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* Set the key schedule of an ICE key.
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*/
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void
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IceKey::set (
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const unsigned char *key
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) {
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int i;
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if (_rounds == 8) {
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unsigned short kb[4];
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for (i=0; i<4; i++)
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kb[3 - i] = (key[i*2] << 8) | key[i*2 + 1];
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scheduleBuild (kb, 0, ice_keyrot);
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return;
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}
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for (i=0; i<_size; i++) {
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int j;
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unsigned short kb[4];
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for (j=0; j<4; j++)
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kb[3 - j] = (key[i*8 + j*2] << 8) | key[i*8 + j*2 + 1];
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scheduleBuild (kb, i*8, ice_keyrot);
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scheduleBuild (kb, _rounds - 8 - i*8, &ice_keyrot[8]);
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}
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}
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/*
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* Return the key size, in bytes.
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*/
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int
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IceKey::keySize () const
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{
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return (_size * 8);
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}
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/*
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* Return the block size, in bytes.
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*/
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int
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IceKey::blockSize () const
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{
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return (8);
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}
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#endif // !_STATIC_LINKED || _SHARED_LIB
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