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Copyright (C) 1999-2007 The Botan Project. All rights reserved.
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Redistribution and use in source and binary forms, for any use, with or without
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modification, is permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this
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list of conditions, and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions, and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) "AS IS" AND ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE DISCLAIMED.
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IN NO EVENT SHALL THE AUTHOR(S) OR CONTRIBUTOR(S) BE LIABLE FOR ANY DIRECT,
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INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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namespace QCA { // WRAPNS_LINE
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/*************************************************
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* Karatsuba Multiplication Source File *
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* (C) 1999-2007 The Botan Project *
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*************************************************/
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#include <botan/mp_core.h>
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namespace QCA { // WRAPNS_LINE
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#include <botan/mem_ops.h>
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namespace QCA { // WRAPNS_LINE
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/*************************************************
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* Simple O(N^2) Multiplication *
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*************************************************/
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void bigint_simple_mul(word z[], const word x[], u32bit x_size,
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const word y[], u32bit y_size)
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clear_mem(z, x_size + y_size);
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for(u32bit j = 0; j != x_size; ++j)
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z[j+y_size] = bigint_mul_add_words(z + j, y, y_size, x[j]);
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/*************************************************
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* Karatsuba Multiplication Operation *
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*************************************************/
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void karatsuba_mul(word z[], const word x[], const word y[], u32bit N,
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const u32bit KARATSUBA_MUL_LOWER_SIZE = BOTAN_KARAT_MUL_THRESHOLD;
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bigint_comba_mul6(z, x, y);
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bigint_comba_mul8(z, x, y);
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else if(N < KARATSUBA_MUL_LOWER_SIZE || N % 2)
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bigint_simple_mul(z, x, N, y, N);
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const u32bit N2 = N / 2;
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const word* x1 = x + N2;
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const word* y1 = y + N2;
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const s32bit cmp0 = bigint_cmp(x0, N2, x1, N2);
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const s32bit cmp1 = bigint_cmp(y1, N2, y0, N2);
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clear_mem(workspace, 2*N);
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bigint_sub3(z0, x0, N2, x1, N2);
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bigint_sub3(z0, x1, N2, x0, N2);
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bigint_sub3(z1, y1, N2, y0, N2);
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bigint_sub3(z1, y0, N2, y1, N2);
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karatsuba_mul(workspace, z0, z1, N2, workspace+N);
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karatsuba_mul(z0, x0, y0, N2, workspace+N);
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karatsuba_mul(z1, x1, y1, N2, workspace+N);
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word carry = bigint_add3_nc(workspace+N, z0, N, z1, N);
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carry += bigint_add2_nc(z + N2, N, workspace + N, N);
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bigint_add2_nc(z + N + N2, N2, &carry, 1);
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if((cmp0 == cmp1) || (cmp0 == 0) || (cmp1 == 0))
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bigint_add2(z + N2, 2*N-N2, workspace, N);
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bigint_sub2(z + N2, 2*N-N2, workspace, N);
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/*************************************************
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* Pick a good size for the Karatsuba multiply *
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*************************************************/
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u32bit karatsuba_size(u32bit z_size,
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u32bit x_size, u32bit x_sw,
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u32bit y_size, u32bit y_sw)
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if(x_sw > x_size || x_sw > y_size || y_sw > x_size || y_sw > y_size)
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if(((x_size == x_sw) && (x_size % 2)) ||
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((y_size == y_sw) && (y_size % 2)))
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u32bit start = (x_sw > y_sw) ? x_sw : y_sw;
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u32bit end = (x_size < y_size) ? x_size : y_size;
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for(u32bit j = start; j <= end; ++j)
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if(x_sw <= j && j <= x_size && y_sw <= j && j <= y_size)
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(j+2) <= x_size && (j+2) <= y_size && 2*(j+2) <= z_size)
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/*************************************************
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* Handle small operand multiplies *
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*************************************************/
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void handle_small_mul(word z[], u32bit z_size,
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const word x[], u32bit x_size, u32bit x_sw,
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const word y[], u32bit y_size, u32bit y_sw)
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if(x_sw == 1) bigint_linmul3(z, y, y_sw, x[0]);
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else if(y_sw == 1) bigint_linmul3(z, x, x_sw, y[0]);
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else if(x_sw <= 4 && x_size >= 4 &&
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y_sw <= 4 && y_size >= 4 && z_size >= 8)
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bigint_comba_mul4(z, x, y);
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else if(x_sw <= 6 && x_size >= 6 &&
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y_sw <= 6 && y_size >= 6 && z_size >= 12)
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bigint_comba_mul6(z, x, y);
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else if(x_sw <= 8 && x_size >= 8 &&
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y_sw <= 8 && y_size >= 8 && z_size >= 16)
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bigint_comba_mul8(z, x, y);
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bigint_simple_mul(z, x, x_sw, y, y_sw);
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/*************************************************
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* Multiplication Algorithm Dispatcher *
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*************************************************/
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void bigint_mul(word z[], u32bit z_size, word workspace[],
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const word x[], u32bit x_size, u32bit x_sw,
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const word y[], u32bit y_size, u32bit y_sw)
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if(x_size <= 8 || y_size <= 8)
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handle_small_mul(z, z_size, x, x_size, x_sw, y, y_size, y_sw);
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const u32bit N = karatsuba_size(z_size, x_size, x_sw, y_size, y_sw);
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clear_mem(workspace, 2*N);
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karatsuba_mul(z, x, y, N, workspace);
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bigint_simple_mul(z, x, x_sw, y, y_sw);