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https://github.com/cryb-to/cryb-to.git
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622 lines
13 KiB
C
622 lines
13 KiB
C
/* NN.C - natural numbers routines
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*/
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/* Copyright (C) RSA Laboratories, a division of RSA Data Security,
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Inc., created 1991. All rights reserved.
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*/
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#include "global.h"
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#include "rsaref.h"
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#include "nn.h"
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#include "digit.h"
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static NN_DIGIT NN_AddDigitMult PROTO_LIST
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((NN_DIGIT *, NN_DIGIT *, NN_DIGIT, NN_DIGIT *, unsigned int));
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static NN_DIGIT NN_SubDigitMult PROTO_LIST
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((NN_DIGIT *, NN_DIGIT *, NN_DIGIT, NN_DIGIT *, unsigned int));
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static unsigned int NN_DigitBits PROTO_LIST ((NN_DIGIT));
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/* Decodes character string b into a, where character string is ordered
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from most to least significant.
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Lengths: a[digits], b[len].
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Assumes b[i] = 0 for i < len - digits * NN_DIGIT_LEN. (Otherwise most
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significant bytes are truncated.)
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*/
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void NN_Decode (a, digits, b, len)
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NN_DIGIT *a;
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unsigned char *b;
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unsigned int digits, len;
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{
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NN_DIGIT t;
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int j;
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unsigned int i, u;
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for (i = 0, j = len - 1; i < digits && j >= 0; i++) {
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t = 0;
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for (u = 0; j >= 0 && u < NN_DIGIT_BITS; j--, u += 8)
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t |= ((NN_DIGIT)b[j]) << u;
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a[i] = t;
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}
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for (; i < digits; i++)
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a[i] = 0;
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}
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/* Encodes b into character string a, where character string is ordered
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from most to least significant.
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Lengths: a[len], b[digits].
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Assumes NN_Bits (b, digits) <= 8 * len. (Otherwise most significant
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digits are truncated.)
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*/
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void NN_Encode (a, len, b, digits)
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NN_DIGIT *b;
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unsigned char *a;
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unsigned int digits, len;
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{
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NN_DIGIT t;
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int j;
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unsigned int i, u;
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for (i = 0, j = len - 1; i < digits && j >= 0; i++) {
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t = b[i];
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for (u = 0; j >= 0 && u < NN_DIGIT_BITS; j--, u += 8)
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a[j] = (unsigned char)(t >> u);
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}
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for (; j >= 0; j--)
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a[j] = 0;
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}
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/* Assigns a = b.
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Lengths: a[digits], b[digits].
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*/
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void NN_Assign (a, b, digits)
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NN_DIGIT *a, *b;
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unsigned int digits;
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{
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unsigned int i;
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for (i = 0; i < digits; i++)
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a[i] = b[i];
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}
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/* Assigns a = 0.
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Lengths: a[digits].
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*/
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void NN_AssignZero (a, digits)
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NN_DIGIT *a;
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unsigned int digits;
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{
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unsigned int i;
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for (i = 0; i < digits; i++)
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a[i] = 0;
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}
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/* Assigns a = 2^b.
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Lengths: a[digits].
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Requires b < digits * NN_DIGIT_BITS.
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*/
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void NN_Assign2Exp (a, b, digits)
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NN_DIGIT *a;
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unsigned int b, digits;
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{
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NN_AssignZero (a, digits);
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if (b >= digits * NN_DIGIT_BITS)
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return;
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a[b / NN_DIGIT_BITS] = (NN_DIGIT)1 << (b % NN_DIGIT_BITS);
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}
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/* Computes a = b + c. Returns carry.
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Lengths: a[digits], b[digits], c[digits].
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*/
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NN_DIGIT NN_Add (a, b, c, digits)
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NN_DIGIT *a, *b, *c;
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unsigned int digits;
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{
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NN_DIGIT ai, carry;
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unsigned int i;
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carry = 0;
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for (i = 0; i < digits; i++) {
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if ((ai = b[i] + carry) < carry)
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ai = c[i];
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else if ((ai += c[i]) < c[i])
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carry = 1;
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else
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carry = 0;
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a[i] = ai;
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}
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return (carry);
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}
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/* Computes a = b - c. Returns borrow.
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Lengths: a[digits], b[digits], c[digits].
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*/
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NN_DIGIT NN_Sub (a, b, c, digits)
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NN_DIGIT *a, *b, *c;
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unsigned int digits;
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{
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NN_DIGIT ai, borrow;
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unsigned int i;
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borrow = 0;
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for (i = 0; i < digits; i++) {
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if ((ai = b[i] - borrow) > (MAX_NN_DIGIT - borrow))
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ai = MAX_NN_DIGIT - c[i];
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else if ((ai -= c[i]) > (MAX_NN_DIGIT - c[i]))
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borrow = 1;
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else
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borrow = 0;
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a[i] = ai;
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}
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return (borrow);
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}
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/* Computes a = b * c.
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Lengths: a[2*digits], b[digits], c[digits].
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Assumes digits < MAX_NN_DIGITS.
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*/
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void NN_Mult (a, b, c, digits)
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NN_DIGIT *a, *b, *c;
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unsigned int digits;
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{
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NN_DIGIT t[2*MAX_NN_DIGITS];
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unsigned int bDigits, cDigits, i;
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NN_AssignZero (t, 2 * digits);
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bDigits = NN_Digits (b, digits);
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cDigits = NN_Digits (c, digits);
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for (i = 0; i < bDigits; i++)
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t[i+cDigits] += NN_AddDigitMult (&t[i], &t[i], b[i], c, cDigits);
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NN_Assign (a, t, 2 * digits);
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/* Zeroize potentially sensitive information.
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*/
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R_memset ((POINTER)t, 0, sizeof (t));
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}
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/* Computes a = b * 2^c (i.e., shifts left c bits), returning carry.
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Lengths: a[digits], b[digits].
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Requires c < NN_DIGIT_BITS.
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*/
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NN_DIGIT NN_LShift (a, b, c, digits)
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NN_DIGIT *a, *b;
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unsigned int c, digits;
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{
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NN_DIGIT bi, carry;
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unsigned int i, t;
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if (c >= NN_DIGIT_BITS)
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return (0);
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t = NN_DIGIT_BITS - c;
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carry = 0;
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for (i = 0; i < digits; i++) {
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bi = b[i];
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a[i] = (bi << c) | carry;
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carry = c ? (bi >> t) : 0;
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}
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return (carry);
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}
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/* Computes a = c div 2^c (i.e., shifts right c bits), returning carry.
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Lengths: a[digits], b[digits].
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Requires: c < NN_DIGIT_BITS.
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*/
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NN_DIGIT NN_RShift (a, b, c, digits)
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NN_DIGIT *a, *b;
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unsigned int c, digits;
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{
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NN_DIGIT bi, carry;
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int i;
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unsigned int t;
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if (c >= NN_DIGIT_BITS)
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return (0);
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t = NN_DIGIT_BITS - c;
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carry = 0;
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for (i = digits - 1; i >= 0; i--) {
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bi = b[i];
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a[i] = (bi >> c) | carry;
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carry = c ? (bi << t) : 0;
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}
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return (carry);
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}
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/* Computes a = c div d and b = c mod d.
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Lengths: a[cDigits], b[dDigits], c[cDigits], d[dDigits].
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Assumes d > 0, cDigits < 2 * MAX_NN_DIGITS,
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dDigits < MAX_NN_DIGITS.
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*/
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void NN_Div (a, b, c, cDigits, d, dDigits)
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NN_DIGIT *a, *b, *c, *d;
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unsigned int cDigits, dDigits;
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{
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NN_DIGIT ai, cc[2*MAX_NN_DIGITS+1], dd[MAX_NN_DIGITS], t;
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int i;
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unsigned int ddDigits, shift;
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ddDigits = NN_Digits (d, dDigits);
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if (ddDigits == 0)
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return;
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/* Normalize operands.
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*/
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shift = NN_DIGIT_BITS - NN_DigitBits (d[ddDigits-1]);
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NN_AssignZero (cc, ddDigits);
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cc[cDigits] = NN_LShift (cc, c, shift, cDigits);
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NN_LShift (dd, d, shift, ddDigits);
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t = dd[ddDigits-1];
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NN_AssignZero (a, cDigits);
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for (i = cDigits-ddDigits; i >= 0; i--) {
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/* Underestimate quotient digit and subtract.
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*/
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if (t == MAX_NN_DIGIT)
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ai = cc[i+ddDigits];
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else
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NN_DigitDiv (&ai, &cc[i+ddDigits-1], t + 1);
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cc[i+ddDigits] -= NN_SubDigitMult (&cc[i], &cc[i], ai, dd, ddDigits);
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/* Correct estimate.
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*/
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while (cc[i+ddDigits] || (NN_Cmp (&cc[i], dd, ddDigits) >= 0)) {
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ai++;
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cc[i+ddDigits] -= NN_Sub (&cc[i], &cc[i], dd, ddDigits);
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}
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a[i] = ai;
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}
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/* Restore result.
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*/
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NN_AssignZero (b, dDigits);
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NN_RShift (b, cc, shift, ddDigits);
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/* Zeroize potentially sensitive information.
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*/
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R_memset ((POINTER)cc, 0, sizeof (cc));
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R_memset ((POINTER)dd, 0, sizeof (dd));
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}
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/* Computes a = b mod c.
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Lengths: a[cDigits], b[bDigits], c[cDigits].
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Assumes c > 0, bDigits < 2 * MAX_NN_DIGITS, cDigits < MAX_NN_DIGITS.
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*/
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void NN_Mod (a, b, bDigits, c, cDigits)
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NN_DIGIT *a, *b, *c;
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unsigned int bDigits, cDigits;
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{
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NN_DIGIT t[2 * MAX_NN_DIGITS];
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NN_Div (t, a, b, bDigits, c, cDigits);
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/* Zeroize potentially sensitive information.
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*/
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R_memset ((POINTER)t, 0, sizeof (t));
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}
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/* Computes a = b * c mod d.
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Lengths: a[digits], b[digits], c[digits], d[digits].
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Assumes d > 0, digits < MAX_NN_DIGITS.
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*/
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void NN_ModMult (a, b, c, d, digits)
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NN_DIGIT *a, *b, *c, *d;
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unsigned int digits;
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{
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NN_DIGIT t[2*MAX_NN_DIGITS];
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NN_Mult (t, b, c, digits);
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NN_Mod (a, t, 2 * digits, d, digits);
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/* Zeroize potentially sensitive information.
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*/
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R_memset ((POINTER)t, 0, sizeof (t));
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}
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/* Computes a = b^c mod d.
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Lengths: a[dDigits], b[dDigits], c[cDigits], d[dDigits].
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Assumes d > 0, cDigits > 0, dDigits < MAX_NN_DIGITS.
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*/
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void NN_ModExp (a, b, c, cDigits, d, dDigits)
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NN_DIGIT *a, *b, *c, *d;
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unsigned int cDigits, dDigits;
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{
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NN_DIGIT bPower[3][MAX_NN_DIGITS], ci, t[MAX_NN_DIGITS];
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int i;
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unsigned int ciBits, j, s;
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/* Store b, b^2 mod d, and b^3 mod d.
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*/
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NN_Assign (bPower[0], b, dDigits);
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NN_ModMult (bPower[1], bPower[0], b, d, dDigits);
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NN_ModMult (bPower[2], bPower[1], b, d, dDigits);
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NN_ASSIGN_DIGIT (t, 1, dDigits);
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cDigits = NN_Digits (c, cDigits);
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for (i = cDigits - 1; i >= 0; i--) {
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ci = c[i];
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ciBits = NN_DIGIT_BITS;
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/* Scan past leading zero bits of most significant digit.
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*/
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if (i == (int)(cDigits - 1)) {
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while (! DIGIT_2MSB (ci)) {
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ci <<= 2;
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ciBits -= 2;
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}
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}
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for (j = 0; j < ciBits; j += 2, ci <<= 2) {
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/* Compute t = t^4 * b^s mod d, where s = two MSB's of ci.
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*/
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NN_ModMult (t, t, t, d, dDigits);
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NN_ModMult (t, t, t, d, dDigits);
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if ((s = DIGIT_2MSB (ci)) != 0)
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NN_ModMult (t, t, bPower[s-1], d, dDigits);
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}
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}
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NN_Assign (a, t, dDigits);
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/* Zeroize potentially sensitive information.
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*/
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R_memset ((POINTER)bPower, 0, sizeof (bPower));
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R_memset ((POINTER)t, 0, sizeof (t));
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}
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/* Compute a = 1/b mod c, assuming inverse exists.
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Lengths: a[digits], b[digits], c[digits].
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Assumes gcd (b, c) = 1, digits < MAX_NN_DIGITS.
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*/
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void NN_ModInv (a, b, c, digits)
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NN_DIGIT *a, *b, *c;
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unsigned int digits;
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{
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NN_DIGIT q[MAX_NN_DIGITS], t1[MAX_NN_DIGITS], t3[MAX_NN_DIGITS],
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u1[MAX_NN_DIGITS], u3[MAX_NN_DIGITS], v1[MAX_NN_DIGITS],
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v3[MAX_NN_DIGITS], w[2*MAX_NN_DIGITS];
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int u1Sign;
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/* Apply extended Euclidean algorithm, modified to avoid negative
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numbers.
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*/
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NN_ASSIGN_DIGIT (u1, 1, digits);
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NN_AssignZero (v1, digits);
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NN_Assign (u3, b, digits);
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NN_Assign (v3, c, digits);
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u1Sign = 1;
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while (! NN_Zero (v3, digits)) {
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NN_Div (q, t3, u3, digits, v3, digits);
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NN_Mult (w, q, v1, digits);
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NN_Add (t1, u1, w, digits);
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NN_Assign (u1, v1, digits);
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NN_Assign (v1, t1, digits);
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NN_Assign (u3, v3, digits);
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NN_Assign (v3, t3, digits);
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u1Sign = -u1Sign;
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}
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/* Negate result if sign is negative.
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*/
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if (u1Sign < 0)
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NN_Sub (a, c, u1, digits);
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else
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NN_Assign (a, u1, digits);
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/* Zeroize potentially sensitive information.
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*/
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R_memset ((POINTER)q, 0, sizeof (q));
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R_memset ((POINTER)t1, 0, sizeof (t1));
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R_memset ((POINTER)t3, 0, sizeof (t3));
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R_memset ((POINTER)u1, 0, sizeof (u1));
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R_memset ((POINTER)u3, 0, sizeof (u3));
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R_memset ((POINTER)v1, 0, sizeof (v1));
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R_memset ((POINTER)v3, 0, sizeof (v3));
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R_memset ((POINTER)w, 0, sizeof (w));
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}
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/* Computes a = gcd(b, c).
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Lengths: a[digits], b[digits], c[digits].
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Assumes b > c, digits < MAX_NN_DIGITS.
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*/
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void NN_Gcd (a, b, c, digits)
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NN_DIGIT *a, *b, *c;
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unsigned int digits;
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{
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NN_DIGIT t[MAX_NN_DIGITS], u[MAX_NN_DIGITS], v[MAX_NN_DIGITS];
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NN_Assign (u, b, digits);
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NN_Assign (v, c, digits);
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while (! NN_Zero (v, digits)) {
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NN_Mod (t, u, digits, v, digits);
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NN_Assign (u, v, digits);
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NN_Assign (v, t, digits);
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}
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NN_Assign (a, u, digits);
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/* Zeroize potentially sensitive information.
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*/
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R_memset ((POINTER)t, 0, sizeof (t));
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R_memset ((POINTER)u, 0, sizeof (u));
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R_memset ((POINTER)v, 0, sizeof (v));
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}
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/* Returns sign of a - b.
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Lengths: a[digits], b[digits].
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*/
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int NN_Cmp (a, b, digits)
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NN_DIGIT *a, *b;
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unsigned int digits;
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{
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int i;
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for (i = digits - 1; i >= 0; i--) {
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if (a[i] > b[i])
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return (1);
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if (a[i] < b[i])
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return (-1);
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}
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return (0);
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}
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/* Returns nonzero iff a is zero.
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Lengths: a[digits].
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*/
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int NN_Zero (a, digits)
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NN_DIGIT *a;
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unsigned int digits;
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{
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unsigned int i;
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for (i = 0; i < digits; i++)
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if (a[i])
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return (0);
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return (1);
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}
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/* Returns the significant length of a in bits.
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Lengths: a[digits].
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*/
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unsigned int NN_Bits (a, digits)
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NN_DIGIT *a;
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unsigned int digits;
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{
|
|
if ((digits = NN_Digits (a, digits)) == 0)
|
|
return (0);
|
|
|
|
return ((digits - 1) * NN_DIGIT_BITS + NN_DigitBits (a[digits-1]));
|
|
}
|
|
|
|
/* Returns the significant length of a in digits.
|
|
|
|
Lengths: a[digits].
|
|
*/
|
|
unsigned int NN_Digits (a, digits)
|
|
NN_DIGIT *a;
|
|
unsigned int digits;
|
|
{
|
|
int i;
|
|
|
|
for (i = digits - 1; i >= 0; i--)
|
|
if (a[i])
|
|
break;
|
|
|
|
return (i + 1);
|
|
}
|
|
|
|
/* Computes a = b + c*d, where c is a digit. Returns carry.
|
|
|
|
Lengths: a[digits], b[digits], d[digits].
|
|
*/
|
|
static NN_DIGIT NN_AddDigitMult (a, b, c, d, digits)
|
|
NN_DIGIT *a, *b, c, *d;
|
|
unsigned int digits;
|
|
{
|
|
NN_DIGIT carry, t[2];
|
|
unsigned int i;
|
|
|
|
if (c == 0)
|
|
return (0);
|
|
|
|
carry = 0;
|
|
for (i = 0; i < digits; i++) {
|
|
NN_DigitMult (t, c, d[i]);
|
|
if ((a[i] = b[i] + carry) < carry)
|
|
carry = 1;
|
|
else
|
|
carry = 0;
|
|
if ((a[i] += t[0]) < t[0])
|
|
carry++;
|
|
carry += t[1];
|
|
}
|
|
|
|
return (carry);
|
|
}
|
|
|
|
/* Computes a = b - c*d, where c is a digit. Returns borrow.
|
|
|
|
Lengths: a[digits], b[digits], d[digits].
|
|
*/
|
|
static NN_DIGIT NN_SubDigitMult (a, b, c, d, digits)
|
|
NN_DIGIT *a, *b, c, *d;
|
|
unsigned int digits;
|
|
{
|
|
NN_DIGIT borrow, t[2];
|
|
unsigned int i;
|
|
|
|
if (c == 0)
|
|
return (0);
|
|
|
|
borrow = 0;
|
|
for (i = 0; i < digits; i++) {
|
|
NN_DigitMult (t, c, d[i]);
|
|
if ((a[i] = b[i] - borrow) > (MAX_NN_DIGIT - borrow))
|
|
borrow = 1;
|
|
else
|
|
borrow = 0;
|
|
if ((a[i] -= t[0]) > (MAX_NN_DIGIT - t[0]))
|
|
borrow++;
|
|
borrow += t[1];
|
|
}
|
|
|
|
return (borrow);
|
|
}
|
|
|
|
/* Returns the significant length of a in bits, where a is a digit.
|
|
*/
|
|
static unsigned int NN_DigitBits (a)
|
|
NN_DIGIT a;
|
|
{
|
|
unsigned int i;
|
|
|
|
for (i = 0; i < NN_DIGIT_BITS; i++, a >>= 1)
|
|
if (a == 0)
|
|
break;
|
|
|
|
return (i);
|
|
}
|