442 lines
8.9 KiB
C++
442 lines
8.9 KiB
C++
/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2016 Danny Robson <danny@nerdcruft.net>
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*/
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// Derived from Mathew Kwan's 1996 C++ public domain implementation of ICE:
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// http://www.darkside.com.au/ice/
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//
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// M. Kwan, The Design of the ICE Encryption Algorithm, proceedings of Fast
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// Software Encryption - Fourth International Workshop, Haifa, Israel,
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// Springer-Verlag, pp. 69-82, 1997
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#include "./ice.hpp"
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#include "../endian.hpp"
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#include "../debug.hpp"
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#include <cstdint>
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///////////////////////////////////////////////////////////////////////////////
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/*
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* C++ implementation of the ICE encryption algorithm.
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*
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* Written by Matthew Kwan - July 1996
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*/
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/* The S-boxes */
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static uint32_t ice_sbox[4][1024];
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static bool ice_sboxes_initialised = false;
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/* Modulo values for the S-boxes */
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static
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constexpr
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uint_fast16_t
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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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};
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/* XOR values for the S-boxes */
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constexpr
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uint8_t
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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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};
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/* Permutation values for the P-box */
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constexpr
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uint32_t
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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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};
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/* The key rotation schedule */
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constexpr
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std::array<uint_fast8_t,8>
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ice_keyrot[2] = {
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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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/*
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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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template <typename T>
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static
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T
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gf_mult (T a, T b, const T m)
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{
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T res = 0;
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while (b) {
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if (b & 1u)
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res ^= a;
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a <<= 1u;
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b >>= 1u;
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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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template <typename T>
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static
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T
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gf_exp7 (const T b,
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const T m)
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{
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if (b == 0)
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return 0;
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T x;
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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
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uint32_t
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ice_perm32 (uint32_t x)
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{
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uint32_t res = 0;
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const uint32_t *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
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void
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ice_sboxes_init (void)
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{
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for (unsigned i = 0; i < 1024; i++) {
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const uint_fast16_t col = (i >> 1) & 0xff;
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const uint_fast16_t row = (i & 0x1) | ((i & 0x200) >> 8);
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for (unsigned j = 0; j < 4; ++j) {
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const auto p = gf_exp7<uint_fast16_t> (
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col ^ ice_sxor[j][row],
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ice_smod[j][row]
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) << (24 - j * 8);
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ice_sbox[j][i] = ice_perm32 (static_cast<uint32_t>(p));
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}
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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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ice::ice (unsigned n,
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const uint64_t *key_first,
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const uint64_t *key_last)
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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 = true;
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}
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if (n < 1) {
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m_size = 1;
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m_rounds = 8;
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} else {
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m_size = n;
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m_rounds = n * 16;
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}
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m_schedule.resize (m_rounds);
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set (key_first, key_last);
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}
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/*
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* Destroy an ICE key.
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*/
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ice::~ice ()
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{
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for (auto &s: m_schedule)
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std::fill (std::begin (s), std::end (s), 0);
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m_rounds = m_size = 0;
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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
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uint32_t
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ice_f (uint32_t p, const ice::subkey_t &sk)
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{
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uint_fast64_t tl, tr; /* Expanded 40-bit values */
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uint_fast64_t 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[2] & (tl ^ tr);
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ar = al ^ tr;
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al ^= tl;
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al ^= sk[0]; /* XOR with the subkey */
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ar ^= sk[1];
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/* S-box lookup and permutation */
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return (
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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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/*
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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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uint64_t
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ice::encrypt (const uint64_t _ptext) const
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{
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union {
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uint64_t pword;
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uint8_t pbytes[8];
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};
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pword = util::hton (_ptext);
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uint32_t l, r;
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l = (((uint32_t) pbytes[0]) << 24u)
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| (((uint32_t) pbytes[1]) << 16u)
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| (((uint32_t) pbytes[2]) << 8u)
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| pbytes[3];
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r = (((uint32_t) pbytes[4]) << 24u)
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| (((uint32_t) pbytes[5]) << 16u)
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| (((uint32_t) pbytes[6]) << 8u)
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| pbytes[7];
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for (unsigned i = 0; i < m_rounds; i += 2) {
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l ^= ice_f (r, m_schedule[i]);
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r ^= ice_f (l, m_schedule[i + 1]);
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}
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union {
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uint64_t cword;
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uint8_t cbytes[8];
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};
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for (unsigned i = 0; i < 4; i++) {
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cbytes[3 - i] = r & 0xff;
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cbytes[7 - i] = l & 0xff;
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r >>= 8u;
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l >>= 8u;
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}
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return util::hton (cword);
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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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uint64_t
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ice::decrypt (const uint64_t _ctext) const
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{
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union {
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uint64_t cword;
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uint8_t cbytes[8];
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};
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cword = util::hton (_ctext);
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uint32_t l, r;
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l = (((uint32_t) cbytes[0]) << 24u)
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| (((uint32_t) cbytes[1]) << 16u)
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| (((uint32_t) cbytes[2]) << 8u)
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| cbytes[3];
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r = (((uint32_t) cbytes[4]) << 24u)
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| (((uint32_t) cbytes[5]) << 16u)
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| (((uint32_t) cbytes[6]) << 8u)
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| cbytes[7];
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for (int i = m_rounds - 1; i > 0; i -= 2) {
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l ^= ice_f (r, m_schedule[i]);
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r ^= ice_f (l, m_schedule[i - 1]);
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}
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union {
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uint64_t pword;
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uint8_t pbytes[8];
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};
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for (unsigned i = 0; i < 4; i++) {
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pbytes[3 - i] = r & 0xff;
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pbytes[7 - i] = l & 0xff;
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r >>= 8;
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l >>= 8;
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}
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return util::hton (pword);
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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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ice::scheduleBuild (std::array<uint16_t,4> &kb,
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int n,
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const std::array<uint_fast8_t,8> &keyrot)
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{
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for (unsigned i = 0; i < 8; i++) {
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int kr = keyrot[i];
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subkey_t &isk = m_schedule[n + i];
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std::fill (std::begin (isk), std::end (isk), 0);
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for (unsigned j = 0; j < 15; j++) {
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uint32_t &curr_sk = isk[j % 3];
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for (unsigned k = 0; k < 4; k++) {
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auto &curr_kb = kb[(kr + k) & 3];
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unsigned 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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ice::set (const uint64_t *_key_first, const uint64_t *_key_last)
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{
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(void)_key_last;
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CHECK_EQ ((unsigned)(_key_last - _key_first), m_size);
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auto key = reinterpret_cast<const uint8_t*> (_key_first);
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if (m_rounds == 8) {
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std::array<uint16_t,4> kb;
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for (unsigned 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[0]);
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return;
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}
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for (unsigned i = 0; i < m_size; i++) {
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std::array<uint16_t,4> kb;
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for (unsigned 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[0]);
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scheduleBuild (kb, m_rounds - 8 - i * 8, ice_keyrot[1]);
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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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unsigned
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ice::key_size () const
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{
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return (m_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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unsigned
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ice::block_size () const
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{
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return (8);
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}
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