--- /dev/null
+/* bigint.c */
+/*
+ This file is part of the AVR-Crypto-Lib.
+ Copyright (C) 2008 Daniel Otte (daniel.otte@rub.de)
+
+ 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 3 of the License, or
+ (at your option) 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, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * \file bigint.c
+ * \author Daniel Otte
+ * \date 2010-02-22
+ *
+ * \license GPLv3 or later
+ *
+ */
+
+
+#define STRING2(x) #x
+#define STRING(x) STRING2(x)
+#define STR_LINE STRING(__LINE__)
+
+#include "bigint.h"
+#include <string.h>
+/*
+#include "cli.h"
+#include "bigint_io.h"
+*/
+#ifndef MAX
+ #define MAX(a,b) (((a)>(b))?(a):(b))
+#endif
+
+#ifndef MIN
+ #define MIN(a,b) (((a)<(b))?(a):(b))
+#endif
+
+#define SET_FBS(a, v) do{(a)->info &=0xF8; (a)->info |= (v);}while(0)
+#define GET_FBS(a) ((a)->info&BIGINT_FBS_MASK)
+#define SET_NEG(a) (a)->info |= BIGINT_NEG_MASK
+#define SET_POS(a) (a)->info &= ~BIGINT_NEG_MASK
+#define XCHG(a,b) do{(a)^=(b); (b)^=(a); (a)^=(b);}while(0)
+#define XCHG_PTR(a,b) do{ a = (void*)(((uint16_t)(a)) ^ ((uint16_t)(b))); \
+ b = (void*)(((uint16_t)(a)) ^ ((uint16_t)(b))); \
+ a = (void*)(((uint16_t)(a)) ^ ((uint16_t)(b)));}while(0)
+
+#define GET_SIGN(a) ((a)->info&BIGINT_NEG_MASK)
+
+
+/******************************************************************************/
+/*
+void bigint_copy(bigint_t* dest, const bigint_t* src){
+ memcpy(dest->wordv, src->wordv, src->length_B);
+ dest->length_B = src->length_B;
+ dest->info = src->info;
+}
+*/
+/******************************************************************************/
+
+/* this should be implemented in assembly */
+/*
+void bigint_add_u(bigint_t* dest, const bigint_t* a, const bigint_t* b){
+ uint16_t t=0, i;
+ if(a->length_B < b->length_B){
+ XCHG_PTR(a,b);
+ }
+ for(i=0; i<b->length_B; ++i){
+ t = a->wordv[i] + b->wordv[i] + t;
+ dest->wordv[i] = (uint8_t)t;
+ t>>=8;
+ }
+ for(; i<a->length_B; ++i){
+ t = a->wordv[i] + t;
+ dest->wordv[i] = (uint8_t)t;
+ t>>=8;
+ }
+ dest->wordv[i++] = t;
+ dest->length_B = i;
+ bigint_adjust(dest);
+}
+*/
+/******************************************************************************/
+
+/* this should be implemented in assembly */
+/*
+void bigint_add_scale_u(bigint_t* dest, const bigint_t* a, uint16_t scale){
+ uint16_t i,j=0;
+ uint16_t t=0;
+ if(scale>dest->length_B)
+ memset(dest->wordv+dest->length_B, 0, scale-dest->length_B);
+ for(i=scale; i<a->length_B+scale; ++i,++j){
+ t = a->wordv[j] + t;
+ if(dest->length_B>i){
+ t += dest->wordv[i];
+ }
+ dest->wordv[i] = (uint8_t)t;
+ t>>=8;
+ }
+ while(t){
+ if(dest->length_B>i){
+ t = dest->wordv[i] + t;
+ }
+ dest->wordv[i] = (uint8_t)t;
+ t>>=8;
+ ++i;
+ }
+ if(dest->length_B < i){
+ dest->length_B = i;
+ }
+ bigint_adjust(dest);
+}
+*/
+/******************************************************************************/
+
+/* this should be implemented in assembly */
+void bigint_sub_u(bigint_t* dest, const bigint_t* a, const bigint_t* b){
+ int8_t borrow=0;
+ int8_t r;
+ int16_t t;
+ uint16_t i, min, max;
+ min = MIN(a->length_B, b->length_B);
+ max = MAX(a->length_B, b->length_B);
+ r = bigint_cmp_u(a,b);
+ if(r==0){
+ dest->length_B = 0;
+ dest->wordv[0] = 0;
+ bigint_adjust(dest);
+ return;
+ }
+ if(b->length_B==0){
+ dest->length_B = a->length_B;
+ memcpy(dest->wordv, a->wordv, a->length_B);
+ dest->info = a->info;
+ SET_POS(dest);
+ return;
+ }
+ if(a->length_B==0){
+ dest->length_B = b->length_B;
+ memcpy(dest->wordv, b->wordv, b->length_B);
+ dest->info = b->info;
+ SET_NEG(dest);
+ return;
+ }
+ if(r<0){
+ bigint_sub_u(dest, b, a);
+ SET_NEG(dest);
+ }else{
+ for(i=0; i<min; ++i){
+ t = a->wordv[i] - b->wordv[i] - borrow;
+ if(t<0){
+ borrow = 1;
+ dest->wordv[i]=(uint8_t)t;
+ }else{
+ borrow = 0;
+ dest->wordv[i]=(uint8_t)t;
+ }
+ }
+ for(;i<max; ++i){
+ t = a->wordv[i] - borrow;
+ if(t<0){
+ borrow = 1;
+ dest->wordv[i]=(uint8_t)t;
+ }else{
+ borrow = 0;
+ dest->wordv[i]=(uint8_t)t;
+ }
+
+ }
+ SET_POS(dest);
+ dest->length_B = i;
+ bigint_adjust(dest);
+ }
+}
+
+/******************************************************************************/
+
+int8_t bigint_cmp_u(const bigint_t* a, const bigint_t* b){
+ if(a->length_B > b->length_B){
+ return 1;
+ }
+ if(a->length_B < b->length_B){
+ return -1;
+ }
+ if(a->length_B==0){
+ return 0;
+ }
+ uint16_t i;
+ i = a->length_B-1;
+ do{
+ if(a->wordv[i]!=b->wordv[i]){
+ if(a->wordv[i]>b->wordv[i]){
+ return 1;
+ }else{
+ return -1;
+ }
+ }
+ }while(i--);
+ return 0;
+}
+
+/******************************************************************************/
+
+void bigint_add_s(bigint_t* dest, const bigint_t* a, const bigint_t* b){
+ uint8_t s;
+ s = GET_SIGN(a)?2:0;
+ s |= GET_SIGN(b)?1:0;
+ switch(s){
+ case 0: /* both positive */
+ bigint_add_u(dest, a,b);
+ SET_POS(dest);
+ break;
+ case 1: /* a positive, b negative */
+ bigint_sub_u(dest, a, b);
+ break;
+ case 2: /* a negative, b positive */
+ bigint_sub_u(dest, b, a);
+ break;
+ case 3: /* both negative */
+ bigint_add_u(dest, a, b);
+ SET_NEG(dest);
+ break;
+ default: /* how can this happen?*/
+ break;
+ }
+}
+
+/******************************************************************************/
+
+void bigint_sub_s(bigint_t* dest, const bigint_t* a, const bigint_t* b){
+ uint8_t s;
+ s = GET_SIGN(a)?2:0;
+ s |= GET_SIGN(b)?1:0;
+ switch(s){
+ case 0: /* both positive */
+ bigint_sub_u(dest, a,b);
+ break;
+ case 1: /* a positive, b negative */
+ bigint_add_u(dest, a, b);
+ SET_POS(dest);
+ break;
+ case 2: /* a negative, b positive */
+ bigint_add_u(dest, a, b);
+ SET_NEG(dest);
+ break;
+ case 3: /* both negative */
+ bigint_sub_u(dest, b, a);
+ break;
+ default: /* how can this happen?*/
+ break;
+ }
+
+}
+
+/******************************************************************************/
+
+int8_t bigint_cmp_s(const bigint_t* a, const bigint_t* b){
+ uint8_t s;
+ if(a->length_B==0 && b->length_B==0){
+ return 0;
+ }
+ s = GET_SIGN(a)?2:0;
+ s |= GET_SIGN(b)?1:0;
+ switch(s){
+ case 0: /* both positive */
+ return bigint_cmp_u(a, b);
+ break;
+ case 1: /* a positive, b negative */
+ return 1;
+ break;
+ case 2: /* a negative, b positive */
+ return -1;
+ break;
+ case 3: /* both negative */
+ return bigint_cmp_u(b, a);
+ break;
+ default: /* how can this happen?*/
+ break;
+ }
+ return 0; /* just to satisfy the compiler */
+}
+
+/******************************************************************************/
+
+void bigint_shiftleft(bigint_t* a, uint16_t shift){
+ uint16_t byteshift;
+ uint16_t i;
+ uint8_t bitshift;
+ uint16_t t=0;
+ byteshift = (shift+3)/8;
+ bitshift = shift&7;
+ memmove(a->wordv+byteshift, a->wordv, a->length_B);
+ memset(a->wordv, 0, byteshift);
+ if(bitshift!=0){
+ if(bitshift<=4){ /* shift to the left */
+ for(i=byteshift; i<a->length_B+byteshift; ++i){
+ t |= (a->wordv[i])<<bitshift;
+ a->wordv[i] = (uint8_t)t;
+ t >>= 8;
+ }
+ a->wordv[i] = (uint8_t)t;
+ byteshift++;
+ }else{ /* shift to the right */
+ for(i=a->length_B+byteshift-1; i>byteshift-1; --i){
+ t |= (a->wordv[i])<<(bitshift);
+ a->wordv[i] = (uint8_t)(t>>8);
+ t <<= 8;
+ }
+ t |= (a->wordv[i])<<(bitshift);
+ a->wordv[i] = (uint8_t)(t>>8);
+ }
+ }
+ a->length_B += byteshift;
+ bigint_adjust(a);
+}
+
+/******************************************************************************/
+
+void bigint_shiftright(bigint_t* a, uint16_t shift){
+ uint16_t byteshift;
+ uint16_t i;
+ uint8_t bitshift;
+ uint16_t t=0;
+ byteshift = shift/8;
+ bitshift = shift&7;
+ if(byteshift >= a->length_B){ /* we would shift out more than we have */
+ bigint_set_zero(a);
+ return;
+ }
+ if(byteshift == a->length_B-1 && bitshift>GET_FBS(a)){
+ bigint_set_zero(a);
+ return;
+ }
+ if(byteshift){
+ memmove(a->wordv, a->wordv+byteshift, a->length_B-byteshift);
+ memset(a->wordv+a->length_B-byteshift, 0, byteshift);
+ }
+ if(bitshift!=0){
+ /* shift to the right */
+ for(i=a->length_B-byteshift-1; i>0; --i){
+ t |= (a->wordv[i])<<(8-bitshift);
+ a->wordv[i] = (uint8_t)(t>>8);
+ t <<= 8;
+ }
+ t |= (a->wordv[0])<<(8-bitshift);
+ a->wordv[0] = (uint8_t)(t>>8);
+ }
+ a->length_B -= byteshift;
+ bigint_adjust(a);
+}
+
+/******************************************************************************/
+
+void bigint_xor(bigint_t* dest, const bigint_t* a){
+ uint16_t i;
+ for(i=0; i<a->length_B; ++i){
+ dest->wordv[i] ^= a->wordv[i];
+ }
+ bigint_adjust(dest);
+}
+
+/******************************************************************************/
+
+void bigint_set_zero(bigint_t* a){
+ a->length_B=0;
+}
+
+/******************************************************************************/
+
+/* using the Karatsuba-Algorithm */
+/* x*y = (xh*yh)*b**2n + ((xh+xl)*(yh+yl) - xh*yh - xl*yl)*b**n + yh*yl */
+void bigint_mul_u(bigint_t* dest, const bigint_t* a, const bigint_t* b){
+ if(a->length_B==0 || b->length_B==0){
+ bigint_set_zero(dest);
+ return;
+ }
+ if(dest==a || dest==b){
+ bigint_t d;
+ uint8_t d_b[a->length_B+b->length_B];
+ d.wordv = d_b;
+ bigint_mul_u(&d, a, b);
+ bigint_copy(dest, &d);
+ return;
+ }
+ if(a->length_B==1 || b->length_B==1){
+ if(a->length_B!=1){
+ XCHG_PTR(a,b);
+ }
+ uint16_t i, t=0;
+ uint8_t x = a->wordv[0];
+ for(i=0; i<b->length_B; ++i){
+ t += b->wordv[i]*x;
+ dest->wordv[i] = (uint8_t)t;
+ t>>=8;
+ }
+ dest->wordv[i] = (uint8_t)t;
+ dest->length_B=i+1;
+ bigint_adjust(dest);
+ return;
+ }
+ if(a->length_B<=4 && b->length_B<=4){
+ uint32_t p=0, q=0;
+ uint64_t r;
+ memcpy(&p, a->wordv, a->length_B);
+ memcpy(&q, b->wordv, b->length_B);
+ r = (uint64_t)p*(uint64_t)q;
+ memcpy(dest->wordv, &r, a->length_B+b->length_B);
+ dest->length_B = a->length_B+b->length_B;
+ bigint_adjust(dest);
+ return;
+ }
+ bigint_set_zero(dest);
+ /* split a in xh & xl; split b in yh & yl */
+ uint16_t n;
+ n=(MAX(a->length_B, b->length_B)+1)/2;
+ bigint_t xl, xh, yl, yh;
+ xl.wordv = a->wordv;
+ yl.wordv = b->wordv;
+ if(a->length_B<=n){
+ xh.info=0;
+ xh.length_B = 0;
+ xl.length_B = a->length_B;
+ xl.info = 0;
+ }else{
+ xl.length_B=n;
+ xl.info = 0;
+ bigint_adjust(&xl);
+ xh.wordv = a->wordv+n;
+ xh.length_B = a->length_B-n;
+ xh.info = 0;
+ }
+ if(b->length_B<=n){
+ yh.info=0;
+ yh.length_B = 0;
+ yl.length_B = b->length_B;
+ yl.info = b->info;
+ }else{
+ yl.length_B=n;
+ yl.info = 0;
+ bigint_adjust(&yl);
+ yh.wordv = b->wordv+n;
+ yh.length_B = b->length_B-n;
+ yh.info = 0;
+ }
+ /* now we have split up a and b */
+ uint8_t tmp_b[2*n+2], m_b[2*(n+1)];
+ bigint_t tmp, tmp2, m;
+ tmp.wordv = tmp_b;
+ tmp2.wordv = tmp_b+n+1;
+ m.wordv = m_b;
+
+ bigint_mul_u(dest, &xl, &yl); /* dest <= xl*yl */
+ bigint_add_u(&tmp2, &xh, &xl); /* tmp2 <= xh+xl */
+ bigint_add_u(&tmp, &yh, &yl); /* tmp <= yh+yl */
+ bigint_mul_u(&m, &tmp2, &tmp); /* m <= tmp2*tmp */
+ bigint_mul_u(&tmp, &xh, &yh); /* h <= xh*yh */
+ bigint_sub_u(&m, &m, dest); /* m <= m-dest */
+ bigint_sub_u(&m, &m, &tmp); /* m <= m-h */
+ bigint_add_scale_u(dest, &m, n);
+ bigint_add_scale_u(dest, &tmp, 2*n);
+}
+
+/******************************************************************************/
+
+void bigint_mul_s(bigint_t* dest, const bigint_t* a, const bigint_t* b){
+ uint8_t s;
+ s = GET_SIGN(a)?2:0;
+ s |= GET_SIGN(b)?1:0;
+ switch(s){
+ case 0: /* both positive */
+ bigint_mul_u(dest, a,b);
+ SET_POS(dest);
+ break;
+ case 1: /* a positive, b negative */
+ bigint_mul_u(dest, a,b);
+ SET_NEG(dest);
+ break;
+ case 2: /* a negative, b positive */
+ bigint_mul_u(dest, a,b);
+ SET_NEG(dest);
+ break;
+ case 3: /* both negative */
+ bigint_mul_u(dest, a,b);
+ SET_POS(dest);
+ break;
+ default: /* how can this happen?*/
+ break;
+ }
+}
+
+/******************************************************************************/
+
+/* square */
+/* (xh*b^n+xl)^2 = xh^2*b^2n + 2*xh*xl*b^n + xl^2 */
+void bigint_square(bigint_t* dest, const bigint_t* a){
+ if(a->length_B<=4){
+ uint64_t r=0;
+ memcpy(&r, a->wordv, a->length_B);
+ r = r*r;
+ memcpy(dest->wordv, &r, 2*a->length_B);
+ SET_POS(dest);
+ dest->length_B=2*a->length_B;
+ bigint_adjust(dest);
+ return;
+ }
+ if(dest==a){
+ bigint_t d;
+ uint8_t d_b[a->length_B*2];
+ d.wordv = d_b;
+ bigint_square(&d, a);
+ bigint_copy(dest, &d);
+ return;
+ }
+ uint16_t n;
+ n=(a->length_B+1)/2;
+ bigint_t xh, xl, tmp; /* x-high, x-low, temp */
+ uint8_t buffer[2*n+1];
+ xl.wordv = a->wordv;
+ xl.length_B = n;
+ xh.wordv = a->wordv+n;
+ xh.length_B = a->length_B-n;
+ tmp.wordv = buffer;
+ bigint_square(dest, &xl);
+ bigint_square(&tmp, &xh);
+ bigint_add_scale_u(dest, &tmp, 2*n);
+ bigint_mul_u(&tmp, &xl, &xh);
+ bigint_shiftleft(&tmp, 1);
+ bigint_add_scale_u(dest, &tmp, n);
+}
+
+/******************************************************************************/
+
+void bigint_sub_u_bitscale(bigint_t* a, const bigint_t* b, uint16_t bitscale){
+ bigint_t tmp;
+ uint8_t tmp_b[b->length_B+1];
+ uint16_t i,j,byteshift=bitscale/8;
+ uint8_t borrow=0;
+ int16_t t;
+
+ if(a->length_B < b->length_B+byteshift){
+ bigint_set_zero(a);
+ return;
+ }
+
+ tmp.wordv = tmp_b;
+ bigint_copy(&tmp, b);
+ bigint_shiftleft(&tmp, bitscale&7);
+
+ for(j=0,i=byteshift; i<tmp.length_B+byteshift; ++i, ++j){
+ t = a->wordv[i] - tmp.wordv[j] - borrow;
+ a->wordv[i] = (uint8_t)t;
+ if(t<0){
+ borrow = 1;
+ }else{
+ borrow = 0;
+ }
+ }
+ while(borrow){
+ if(i+1 > a->length_B){
+ bigint_set_zero(a);
+ return;
+ }
+ a->wordv[i] -= borrow;
+ if(a->wordv[i]!=0xff){
+ borrow=0;
+ }
+ ++i;
+ }
+ bigint_adjust(a);
+}
+
+/******************************************************************************/
+
+void bigint_reduce(bigint_t* a, const bigint_t* r){
+// bigint_adjust(r);
+ uint8_t rfbs = GET_FBS(r);
+
+ if(r->length_B==0 || a->length_B==0){
+ return;
+ }
+ while(a->length_B > r->length_B){
+ bigint_sub_u_bitscale(a, r, (a->length_B-r->length_B)*8+GET_FBS(a)-rfbs-1);
+ }
+ while((GET_FBS(a) > rfbs+1) && (a->length_B == r->length_B)){
+ bigint_sub_u_bitscale(a, r, GET_FBS(a)-rfbs-1);
+ }
+ while(bigint_cmp_u(a,r)>=0){
+ bigint_sub_u(a,a,r);
+ }
+ bigint_adjust(a);
+}
+
+/******************************************************************************/
+
+/* calculate dest = a**exp % r */
+/* using square&multiply */
+void bigint_expmod_u(bigint_t* dest, const bigint_t* a, const bigint_t* exp, const bigint_t* r){
+ if(a->length_B==0 || r->length_B==0){
+ return;
+ }
+
+ bigint_t res, base;
+ uint8_t base_b[MAX(a->length_B,r->length_B*2)], res_b[r->length_B*2];
+ uint16_t i;
+ uint8_t j, t;
+ res.wordv = res_b;
+ base.wordv = base_b;
+ bigint_copy(&base, a);
+ bigint_reduce(&base, r);
+ res.wordv[0]=1;
+ res.length_B=1;
+ res.info = 0;
+ bigint_adjust(&res);
+ for(i=0; i+1<exp->length_B; ++i){
+ t=exp->wordv[i];
+ for(j=0; j<8; ++j){
+ if(t&1){
+ bigint_mul_u(&res, &res, &base);
+ bigint_reduce(&res, r);
+ }
+ bigint_square(&base, &base);
+ bigint_reduce(&base, r);
+ t>>=1;
+ }
+ }
+ t=exp->wordv[i];
+ while(t){
+ if(t&1){
+ bigint_mul_u(&res, &res, &base);
+ bigint_reduce(&res, r);
+ }
+ bigint_square(&base, &base);
+ bigint_reduce(&base, r);
+ t>>=1;
+ }
+ SET_POS(&res);
+ bigint_copy(dest, &res);
+}
+
+/******************************************************************************/
+/* gcd <-- gcd(x,y) a*x+b*y=gcd */
+void bigint_gcdext(bigint_t* gcd, bigint_t* a, bigint_t* b, const bigint_t* x, const bigint_t* y){
+ bigint_t g, x_, y_, u, v, a_, b_, c_, d_;
+ volatile uint16_t i=0;
+ if(x->length_B==0 || y->length_B==0){
+ return;
+ }
+ while(x->wordv[i]==0 && y->wordv[i]==0){
+ ++i;
+ }
+ uint8_t g_b[i+2], x_b[x->length_B-i], y_b[y->length_B-i];
+ uint8_t u_b[x->length_B-i], v_b[y->length_B-i];
+ uint8_t a_b[y->length_B+2], c_b[y->length_B+2];
+ uint8_t b_b[x->length_B+2], d_b[x->length_B+2];
+
+ g.wordv = g_b;
+ x_.wordv = x_b;
+ y_.wordv = y_b;
+ memset(g_b, 0, i);
+ g_b[i]=1;
+ g.length_B = i+1;
+ g.info=0;
+ x_.info = y_.info = 0;
+ x_.length_B = x->length_B-i;
+ y_.length_B = y->length_B-i;
+ memcpy(x_.wordv, x->wordv+i, x_.length_B);
+ memcpy(y_.wordv, y->wordv+i, y_.length_B);
+ for(i=0; (x_.wordv[0]&(1<<i))==0 && (y_.wordv[0]&(1<<i))==0; ++i){
+ }
+
+ bigint_adjust(&x_);
+ bigint_adjust(&y_);
+
+ if(i){
+ bigint_shiftleft(&g, i);
+ bigint_shiftright(&x_, i);
+ bigint_shiftright(&y_, i);
+ }
+ u.wordv = u_b;
+ v.wordv = v_b;
+ a_.wordv = a_b;
+ b_.wordv = b_b;
+ c_.wordv = c_b;
+ d_.wordv = d_b;
+
+ bigint_copy(&u, &x_);
+ bigint_copy(&v, &y_);
+ a_.wordv[0] = 1;
+ a_.length_B = 1;
+ a_.info = 0;
+ d_.wordv[0] = 1;
+ d_.length_B = 1;
+ d_.info = 0;
+ bigint_set_zero(&b_);
+ bigint_set_zero(&c_);
+ do{
+ while((u.wordv[0]&1)==0){
+ bigint_shiftright(&u, 1);
+ if((a_.wordv[0]&1) || (b_.wordv[0]&1)){
+ bigint_add_s(&a_, &a_, &y_);
+ bigint_sub_s(&b_, &b_, &x_);
+ }
+ bigint_shiftright(&a_, 1);
+ bigint_shiftright(&b_, 1);
+ }
+ while((v.wordv[0]&1)==0){
+ bigint_shiftright(&v, 1);
+ if((c_.wordv[0]&1) || (d_.wordv[0]&1)){
+ bigint_add_s(&c_, &c_, &y_);
+ bigint_sub_s(&d_, &d_, &x_);
+ }
+ bigint_shiftright(&c_, 1);
+ bigint_shiftright(&d_, 1);
+
+ }
+ if(bigint_cmp_u(&u, &v)>=0){
+ bigint_sub_u(&u, &u, &v);
+ bigint_sub_s(&a_, &a_, &c_);
+ bigint_sub_s(&b_, &b_, &d_);
+ }else{
+ bigint_sub_u(&v, &v, &u);
+ bigint_sub_s(&c_, &c_, &a_);
+ bigint_sub_s(&d_, &d_, &b_);
+ }
+ }while(u.length_B);
+ if(gcd){
+ bigint_mul_s(gcd, &v, &g);
+ }
+ if(a){
+ bigint_copy(a, &c_);
+ }
+ if(b){
+ bigint_copy(b, &d_);
+ }
+}
+
+/******************************************************************************/
+
+void bigint_inverse(bigint_t* dest, const bigint_t* a, const bigint_t* m){
+ bigint_gcdext(NULL, dest, NULL, a, m);
+ while(dest->info&BIGINT_NEG_MASK){
+ bigint_add_s(dest, dest, m);
+ }
+}
+
+/******************************************************************************/
+
+void bigint_changeendianess(bigint_t* a){
+ uint8_t t, *p, *q;
+ p = a->wordv;
+ q = p+a->length_B-1;
+ while(p<q){
+ t = *p;
+ *p = *q;
+ *q = t;
+ ++p; --q;
+ }
+}
+
+/******************************************************************************/
+
+
+
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projects / avr-crypto-lib.git / commitdiff