From 465cdf0bcbbcd7f18c097beae1e9f85f9da0e04d Mon Sep 17 00:00:00 2001
From: Paul Selkirk <paul@psgd.org>
Date: Sat, 14 Mar 2020 14:11:53 -0400
Subject: Moved modexpng from user/shatov to core/math.

Changed all copyrights from Nordunet to Commons Conservancy, since they've
been the copyright holder since the end of 2018.
---
 stm32/modexpng_util.c | 228 --------------------------------------------------
 1 file changed, 228 deletions(-)
 delete mode 100644 stm32/modexpng_util.c

(limited to 'stm32/modexpng_util.c')

diff --git a/stm32/modexpng_util.c b/stm32/modexpng_util.c
deleted file mode 100644
index d109786..0000000
--- a/stm32/modexpng_util.c
+++ /dev/null
@@ -1,228 +0,0 @@
-//------------------------------------------------------------------------------
-//
-// modexpng_util.c
-// ------------------------------------------------------
-// Helper precomputation routines for the "modexpng" core
-//
-// Authors: Pavel Shatov
-//
-// Copyright (c) 2019, NORDUnet A/S
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are met:
-//
-// - Redistributions of source code must retain the above copyright notice,
-//   this list of conditions and the following disclaimer.
-//
-// - Redistributions in binary form must reproduce the above copyright notice,
-//   this list of conditions and the following disclaimer in the documentation
-//   and/or other materials provided with the distribution.
-//
-// - Neither the name of the NORDUnet nor the names of its contributors may be
-//   used to endorse or promote products derived from this software without
-//   specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
-// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
-// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
-// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
-// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
-// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
-// POSSIBILITY OF SUCH DAMAGE.
-//
-//------------------------------------------------------------------------------
-
-
-//
-// headers
-//
-#include "modexpng_util.h"
-
-
-//
-// internal buffers
-//
-static uint32_t MOD_FACTOR_N[BUF_NUM_WORDS];
-static uint32_t MOD_NN[BUF_NUM_WORDS+1];
-static uint32_t MOD_T[BUF_NUM_WORDS+1];
-
-static void _add32(uint32_t, uint32_t, uint32_t, uint32_t *, uint32_t *);
-static void _sub32(uint32_t, uint32_t, uint32_t, uint32_t *, uint32_t *);
-static void _mul32(uint32_t, uint32_t, uint32_t, uint32_t, uint32_t *, uint32_t *);
-
-
-//
-// calculation of the Montgomery factor
-//
-void _calc_montgomery_factor(uint32_t num_words, const uint32_t *N, uint32_t *N_FACTOR)
-{
-		// counters
-		uint32_t i, j;		
-
-		// flag
-		uint32_t flag_keep;
-
-		// carry and borrow
-		uint32_t cry_in, cry_out;
-		uint32_t brw_in, brw_out;
-
-		// initially set N_FACTOR = 1
-		for (i=0; i<num_words; i++)
-				N_FACTOR[i] = i ? 0 : 1;
-		
-		// do the math
-		for (i=0; i<2*(num_words * UINT32_BITS + UINT16_BITS); i++)
-		{	
-				// clear carry and borrow
-				cry_in = 0, brw_in = 0;
-		
-				// calculate N_FACTOR = N_FACTOR << 1, MOD_FACTOR_N = N_FACTOR - N
-				for (j=0; j<num_words; j++)
-				{
-						cry_out = N_FACTOR[j] >> (UINT32_BITS - 1);		// | N_FACTOR <<= 1
-						N_FACTOR[j] <<= 1; N_FACTOR[j] |= cry_in;			// |
-
-						_sub32(N_FACTOR[j], N[j], brw_in, &MOD_FACTOR_N[j], &brw_out);	// MOD_FACTOR_N = N_FACTOR - N
-	
-						// propagate carry & borrow
-						cry_in = cry_out, brw_in = brw_out;
-				}
-
-				// obtain flag
-				flag_keep = brw_out && !cry_out;
-
-				// now select the right value
-				for (j=0; j<num_words; j++)
-						N_FACTOR[j] = flag_keep ? N_FACTOR[j] : MOD_FACTOR_N[j];
-		}
-}
-
-
-//
-// calculation of the modulus-dependent speed-up coefficient
-//
-void _calc_modulus_coeff(uint32_t num_words, const uint32_t *N, uint32_t *N_COEFF)
-{
-		// counters
-		uint32_t i, j, k, jk;
-
-		// indices
-		uint32_t word_index, bit_index;
-
-		// flag
-		uint32_t flag_update;
-	
-		// carries
-		uint32_t cry_in, cry_out;
-	
-		// temporary variables
-		uint32_t mod_p, add_s, b_word;
-	
-		// initially set N_COEFF to 1
-		for (i=0; i<=num_words; i++)
-				N_COEFF[i] = i ? 0 : 1;
-
-		// also set NN to ~N+1
-		// note that since N must be odd, ~N is even, so adding 1 to it doesn't need
-		// any carry propagation
-		for (i=0; i<num_words; i++) MOD_NN[i] = ~N[i];
-		MOD_NN[0] += 1;
-		MOD_NN[num_words] = 0xffffffff;
-        
-		// do the math
-		for (i=1; i<(num_words * UINT32_BITS + UINT16_BITS); i++)
-		{
-				word_index = i / UINT32_BITS;
-			  bit_index = i & (UINT32_BITS - 1);
-
-				// clear T
-				for (j=0; j<=num_words; j++) MOD_T[j] = 0;
-				
-				// T = N_COEFF * NN mod 2 ** (modulus_length + 16)
-				/*
-			   * Note, that we only need the lower half of the product T, so in
-			   * the outer loop we always scan entire N_COEFF, but the inner
-				 * loop only scans entire NN during the first iteration, and then
-			   * keeps skipping one more word every iteration, during the last
-				 * iteration we only scan one word of NN.
-			   *
-			   */
-				for (j=0; j<=num_words; j++)
-				{   cry_in = 0;
-						for (k=0; k<=(num_words-j); k++)
-						{		jk = j + k;
-								_mul32(N_COEFF[j], MOD_NN[k], MOD_T[jk], cry_in, &mod_p, &cry_out);
-								MOD_T[jk] = mod_p;
-								cry_in = cry_out;
-								if (word_index == jk)
-										flag_update = MOD_T[jk] & (1 << bit_index) ? 1 : 0;
-						}
-				}
-				if (flag_update)
-				{		cry_in = 0;
-						for (j=0; j<=num_words; j++)
-						{		b_word = (j == word_index) ? (1 << bit_index) : 0;
-								_add32(b_word, N_COEFF[j], cry_in, &add_s, &cry_out);
-								N_COEFF[j] = add_s;
-								cry_in = cry_out;
-						}
-				}
-		}
-}
-
-
-//
-// low-level addition w/ carry
-//
-static void _add32(uint32_t a, uint32_t b, uint32_t c_in, uint32_t *s, uint32_t *c_out)
-{
-		uint64_t t;															// intermediate var
-	
-		t = (uint64_t)a + (uint64_t)b;					// obtain "wide" difference
-		t += (uint64_t)(c_in & 1);							// take borrow into account
-	
-		*s = (uint32_t)t;												// return the lower part of result
-		*c_out = (uint32_t)(t >> UINT32_BITS);	// return the higher part of result, ...
-		*c_out &= (uint32_t)1;									// ...but truncate it to 1 bit
-}
-
-
-//
-// low-level subtraction w/ borrow
-//
-static void _sub32(uint32_t a, uint32_t b, uint32_t b_in, uint32_t *d, uint32_t *b_out)
-{
-		uint64_t t;															// intermediate var
-	
-		t = (uint64_t)a - (uint64_t)b;					// obtain "wide" difference
-		t -= (uint64_t)(b_in & 1);							// take borrow into account
-	
-		*d = (uint32_t)t;												// return the lower part of result
-		*b_out = (uint32_t)(t >> UINT32_BITS);	// return the higher part of result, ...
-		*b_out &= (uint32_t)1;									// ...but truncate it to 1 bit
-}
-
-
-//
-// low-level multiplication w/ carry and pre-adder
-//
-static void _mul32(uint32_t a, uint32_t b, uint32_t t, uint32_t c_in, uint32_t *p, uint32_t *c_out)
-{
-		uint64_t r;															// intermediate result
-	
-		r = (uint64_t)a * (uint64_t)b;					// obtain wide product
-		r += (uint64_t)t;												// handle pre-addition
-		r += (uint64_t)c_in;										// take carry into account
-	
-		*p = (uint32_t)r;												// return the lower part of result
-		*c_out = (uint32_t)(r >> UINT32_BITS);	// return the higher part of result, ...
-}
-
-
-//
-// end-of-file
-//
-- 
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