[crypto] Add big-integer library for RSA calculations

RSA requires modular exponentiation using arbitrarily large integers. Given the sizes of the modulus and exponent, all required calculations can be done without any further dynamic storage allocation. The x86 architecture allows for efficient large integer support via inline assembly using the instructions that take advantage of the carry flag (e.g. "adcl", "rcrl"). This implemention is approximately 80% smaller than the (more generic) AXTLS implementation. Signed-off-by: Michael Brown <mcb30@ipxe.org>
2025-12-29 02:52:36 +03:00 · 2012-03-13 16:35:21 +00:00
parent f229162749
commit 071184a6e4
5 changed files with 798 additions and 0 deletions
--- a/src/arch/x86/core/x86_bigint.c
+++ b/src/arch/x86/core/x86_bigint.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <string.h>
+#include <ipxe/bigint.h>
+
+/** @file
+ *
+ * Big integer support
+ */
+
+/**
+ * Multiply big integers
+ *
+ * @v multiplicand0	Element 0 of big integer to be multiplied
+ * @v multiplier0	Element 0 of big integer to be multiplied
+ * @v result0		Element 0 of big integer to hold result
+ * @v size		Number of elements
+ */
+void bigint_multiply_raw ( const uint32_t *multiplicand0,
+			   const uint32_t *multiplier0,
+			   uint32_t *result0, unsigned int size ) {
+	const bigint_t ( size ) __attribute__ (( may_alias )) *multiplicand =
+		( ( const void * ) multiplicand0 );
+	const bigint_t ( size ) __attribute__ (( may_alias )) *multiplier =
+		( ( const void * ) multiplier0 );
+	bigint_t ( size * 2 ) __attribute__ (( may_alias )) *result =
+		( ( void * ) result0 );
+	unsigned int i;
+	unsigned int j;
+	uint32_t multiplicand_element;
+	uint32_t multiplier_element;
+	uint32_t *result_elements;
+	uint32_t discard_a;
+	uint32_t discard_d;
+	long index;
+
+	/* Zero result */
+	memset ( result, 0, sizeof ( *result ) );
+
+	/* Multiply integers one element at a time */
+	for ( i = 0 ; i < size ; i++ ) {
+		multiplicand_element = multiplicand->element[i];
+		for ( j = 0 ; j < size ; j++ ) {
+			multiplier_element = multiplier->element[j];
+			result_elements = &result->element[ i + j ];
+			/* Perform a single multiply, and add the
+			 * resulting double-element into the result,
+			 * carrying as necessary.  The carry can
+			 * never overflow beyond the end of the
+			 * result, since:
+			 *
+			 *     a < 2^{n}, b < 2^{n} => ab < 2^{2n}
+			 */
+			__asm__ __volatile__ ( "mull %4\n\t"
+					       "addl %%eax, (%5,%2,4)\n\t"
+					       "adcl %%edx, 4(%5,%2,4)\n\t"
+					       "\n1:\n\t"
+					       "adcl $0, 8(%5,%2,4)\n\t"
+					       "inc %2\n\t"
+						       /* Does not affect CF */
+					       "jc 1b\n\t"
+					       : "=&a" ( discard_a ),
+						 "=&d" ( discard_d ),
+						 "=&r" ( index )
+					       : "0" ( multiplicand_element ),
+						 "g" ( multiplier_element ),
+						 "r" ( result_elements ),
+						 "2" ( 0 ) );
+		}
+	}
+}