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https://github.com/servalproject/serval-dna.git
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bf9710fd5a
This only affects build_android, if nacl-gcc-prep is run then build/`uname -s` will be created.
346 lines
8.2 KiB
C
346 lines
8.2 KiB
C
#include "fe25519.h"
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#define WINDOWSIZE 4 /* Should be 1,2, or 4 */
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#define WINDOWMASK ((1<<WINDOWSIZE)-1)
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static void reduce_add_sub(fe25519 *r)
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{
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crypto_uint32 t;
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int i,rep;
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for(rep=0;rep<4;rep++)
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{
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t = r->v[31] >> 7;
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r->v[31] &= 127;
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t *= 19;
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r->v[0] += t;
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for(i=0;i<31;i++)
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{
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t = r->v[i] >> 8;
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r->v[i+1] += t;
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r->v[i] &= 255;
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}
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}
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}
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static void reduce_mul(fe25519 *r)
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{
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crypto_uint32 t;
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int i,rep;
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for(rep=0;rep<2;rep++)
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{
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t = r->v[31] >> 7;
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r->v[31] &= 127;
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t *= 19;
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r->v[0] += t;
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for(i=0;i<31;i++)
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{
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t = r->v[i] >> 8;
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r->v[i+1] += t;
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r->v[i] &= 255;
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}
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}
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}
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/* reduction modulo 2^255-19 */
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static void freeze(fe25519 *r)
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{
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int i;
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unsigned int m = (r->v[31] == 127);
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for(i=30;i>1;i--)
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m *= (r->v[i] == 255);
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m *= (r->v[0] >= 237);
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r->v[31] -= m*127;
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for(i=30;i>0;i--)
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r->v[i] -= m*255;
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r->v[0] -= m*237;
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}
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/*freeze input before calling isone*/
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static int isone(const fe25519 *x)
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{
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int i;
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int r = (x->v[0] == 1);
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for(i=1;i<32;i++)
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r *= (x->v[i] == 0);
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return r;
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}
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/*freeze input before calling iszero*/
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static int iszero(const fe25519 *x)
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{
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int i;
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int r = (x->v[0] == 0);
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for(i=1;i<32;i++)
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r *= (x->v[i] == 0);
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return r;
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}
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static int issquare(const fe25519 *x)
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{
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unsigned char e[32] = {0xf6,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x3f}; /* (p-1)/2 */
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fe25519 t;
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fe25519_pow(&t,x,e);
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freeze(&t);
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return isone(&t) || iszero(&t);
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}
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void fe25519_unpack(fe25519 *r, const unsigned char x[32])
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{
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int i;
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for(i=0;i<32;i++) r->v[i] = x[i];
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r->v[31] &= 127;
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}
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/* Assumes input x being reduced mod 2^255 */
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void fe25519_pack(unsigned char r[32], const fe25519 *x)
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{
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int i;
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for(i=0;i<32;i++)
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r[i] = x->v[i];
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/* freeze byte array */
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unsigned int m = (r[31] == 127); /* XXX: some compilers might use branches; fix */
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for(i=30;i>1;i--)
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m *= (r[i] == 255);
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m *= (r[0] >= 237);
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r[31] -= m*127;
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for(i=30;i>0;i--)
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r[i] -= m*255;
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r[0] -= m*237;
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}
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void fe25519_cmov(fe25519 *r, const fe25519 *x, unsigned char b)
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{
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unsigned char nb = 1-b;
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int i;
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for(i=0;i<32;i++) r->v[i] = nb * r->v[i] + b * x->v[i];
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}
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unsigned char fe25519_getparity(const fe25519 *x)
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{
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fe25519 t;
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int i;
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for(i=0;i<32;i++) t.v[i] = x->v[i];
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freeze(&t);
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return t.v[0] & 1;
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}
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void fe25519_setone(fe25519 *r)
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{
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int i;
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r->v[0] = 1;
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for(i=1;i<32;i++) r->v[i]=0;
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}
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void fe25519_setzero(fe25519 *r)
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{
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int i;
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for(i=0;i<32;i++) r->v[i]=0;
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}
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void fe25519_neg(fe25519 *r, const fe25519 *x)
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{
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fe25519 t;
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int i;
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for(i=0;i<32;i++) t.v[i]=x->v[i];
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fe25519_setzero(r);
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fe25519_sub(r, r, &t);
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}
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void fe25519_add(fe25519 *r, const fe25519 *x, const fe25519 *y)
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{
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int i;
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for(i=0;i<32;i++) r->v[i] = x->v[i] + y->v[i];
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reduce_add_sub(r);
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}
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void fe25519_sub(fe25519 *r, const fe25519 *x, const fe25519 *y)
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{
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int i;
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crypto_uint32 t[32];
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t[0] = x->v[0] + 0x1da;
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t[31] = x->v[31] + 0xfe;
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for(i=1;i<31;i++) t[i] = x->v[i] + 0x1fe;
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for(i=0;i<32;i++) r->v[i] = t[i] - y->v[i];
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reduce_add_sub(r);
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}
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void fe25519_mul(fe25519 *r, const fe25519 *x, const fe25519 *y)
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{
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int i,j;
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crypto_uint32 t[63];
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for(i=0;i<63;i++)t[i] = 0;
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for(i=0;i<32;i++)
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for(j=0;j<32;j++)
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t[i+j] += x->v[i] * y->v[j];
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for(i=32;i<63;i++)
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r->v[i-32] = t[i-32] + 38*t[i];
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r->v[31] = t[31]; /* result now in r[0]...r[31] */
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reduce_mul(r);
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}
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void fe25519_square(fe25519 *r, const fe25519 *x)
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{
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fe25519_mul(r, x, x);
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}
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/*XXX: Make constant time! */
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void fe25519_pow(fe25519 *r, const fe25519 *x, const unsigned char *e)
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{
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/*
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fe25519 g;
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fe25519_setone(&g);
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int i;
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unsigned char j;
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for(i=32;i>0;i--)
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{
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for(j=128;j>0;j>>=1)
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{
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fe25519_square(&g,&g);
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if(e[i-1] & j)
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fe25519_mul(&g,&g,x);
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}
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}
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for(i=0;i<32;i++) r->v[i] = g.v[i];
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*/
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fe25519 g;
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fe25519_setone(&g);
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int i,j,k;
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fe25519 pre[(1 << WINDOWSIZE)];
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fe25519 t;
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unsigned char w;
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// Precomputation
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fe25519_setone(pre);
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pre[1] = *x;
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for(i=2;i<(1<<WINDOWSIZE);i+=2)
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{
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fe25519_square(pre+i, pre+i/2);
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fe25519_mul(pre+i+1, pre+i, pre+1);
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}
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// Fixed-window scalar multiplication
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for(i=32;i>0;i--)
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{
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for(j=8-WINDOWSIZE;j>=0;j-=WINDOWSIZE)
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{
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for(k=0;k<WINDOWSIZE;k++)
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fe25519_square(&g, &g);
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// Cache-timing resistant loading of precomputed value:
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w = (e[i-1]>>j) & WINDOWMASK;
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t = pre[0];
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for(k=1;k<(1<<WINDOWSIZE);k++)
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fe25519_cmov(&t, &pre[k], k==w);
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fe25519_mul(&g, &g, &t);
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}
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}
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*r = g;
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}
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/* Return 0 on success, 1 otherwise */
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int fe25519_sqrt_vartime(fe25519 *r, const fe25519 *x, unsigned char parity)
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{
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/* See HAC, Alg. 3.37 */
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if (!issquare(x)) return -1;
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unsigned char e[32] = {0xfb,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x1f}; /* (p-1)/4 */
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unsigned char e2[32] = {0xfe,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x0f}; /* (p+3)/8 */
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unsigned char e3[32] = {0xfd,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x0f}; /* (p-5)/8 */
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fe25519 p = {{0}};
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fe25519 d;
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int i;
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fe25519_pow(&d,x,e);
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freeze(&d);
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if(isone(&d))
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fe25519_pow(r,x,e2);
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else
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{
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for(i=0;i<32;i++)
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d.v[i] = 4*x->v[i];
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fe25519_pow(&d,&d,e3);
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for(i=0;i<32;i++)
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r->v[i] = 2*x->v[i];
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fe25519_mul(r,r,&d);
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}
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freeze(r);
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if((r->v[0] & 1) != (parity & 1))
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{
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fe25519_sub(r,&p,r);
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}
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return 0;
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}
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void fe25519_invert(fe25519 *r, const fe25519 *x)
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{
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fe25519 z2;
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fe25519 z9;
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fe25519 z11;
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fe25519 z2_5_0;
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fe25519 z2_10_0;
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fe25519 z2_20_0;
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fe25519 z2_50_0;
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fe25519 z2_100_0;
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fe25519 t0;
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fe25519 t1;
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int i;
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/* 2 */ fe25519_square(&z2,x);
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/* 4 */ fe25519_square(&t1,&z2);
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/* 8 */ fe25519_square(&t0,&t1);
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/* 9 */ fe25519_mul(&z9,&t0,x);
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/* 11 */ fe25519_mul(&z11,&z9,&z2);
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/* 22 */ fe25519_square(&t0,&z11);
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/* 2^5 - 2^0 = 31 */ fe25519_mul(&z2_5_0,&t0,&z9);
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/* 2^6 - 2^1 */ fe25519_square(&t0,&z2_5_0);
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/* 2^7 - 2^2 */ fe25519_square(&t1,&t0);
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/* 2^8 - 2^3 */ fe25519_square(&t0,&t1);
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/* 2^9 - 2^4 */ fe25519_square(&t1,&t0);
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/* 2^10 - 2^5 */ fe25519_square(&t0,&t1);
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/* 2^10 - 2^0 */ fe25519_mul(&z2_10_0,&t0,&z2_5_0);
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/* 2^11 - 2^1 */ fe25519_square(&t0,&z2_10_0);
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/* 2^12 - 2^2 */ fe25519_square(&t1,&t0);
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/* 2^20 - 2^10 */ for (i = 2;i < 10;i += 2) { fe25519_square(&t0,&t1); fe25519_square(&t1,&t0); }
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/* 2^20 - 2^0 */ fe25519_mul(&z2_20_0,&t1,&z2_10_0);
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/* 2^21 - 2^1 */ fe25519_square(&t0,&z2_20_0);
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/* 2^22 - 2^2 */ fe25519_square(&t1,&t0);
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/* 2^40 - 2^20 */ for (i = 2;i < 20;i += 2) { fe25519_square(&t0,&t1); fe25519_square(&t1,&t0); }
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/* 2^40 - 2^0 */ fe25519_mul(&t0,&t1,&z2_20_0);
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/* 2^41 - 2^1 */ fe25519_square(&t1,&t0);
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/* 2^42 - 2^2 */ fe25519_square(&t0,&t1);
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/* 2^50 - 2^10 */ for (i = 2;i < 10;i += 2) { fe25519_square(&t1,&t0); fe25519_square(&t0,&t1); }
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/* 2^50 - 2^0 */ fe25519_mul(&z2_50_0,&t0,&z2_10_0);
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/* 2^51 - 2^1 */ fe25519_square(&t0,&z2_50_0);
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/* 2^52 - 2^2 */ fe25519_square(&t1,&t0);
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/* 2^100 - 2^50 */ for (i = 2;i < 50;i += 2) { fe25519_square(&t0,&t1); fe25519_square(&t1,&t0); }
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/* 2^100 - 2^0 */ fe25519_mul(&z2_100_0,&t1,&z2_50_0);
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/* 2^101 - 2^1 */ fe25519_square(&t1,&z2_100_0);
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/* 2^102 - 2^2 */ fe25519_square(&t0,&t1);
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/* 2^200 - 2^100 */ for (i = 2;i < 100;i += 2) { fe25519_square(&t1,&t0); fe25519_square(&t0,&t1); }
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/* 2^200 - 2^0 */ fe25519_mul(&t1,&t0,&z2_100_0);
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/* 2^201 - 2^1 */ fe25519_square(&t0,&t1);
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/* 2^202 - 2^2 */ fe25519_square(&t1,&t0);
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/* 2^250 - 2^50 */ for (i = 2;i < 50;i += 2) { fe25519_square(&t0,&t1); fe25519_square(&t1,&t0); }
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/* 2^250 - 2^0 */ fe25519_mul(&t0,&t1,&z2_50_0);
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/* 2^251 - 2^1 */ fe25519_square(&t1,&t0);
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/* 2^252 - 2^2 */ fe25519_square(&t0,&t1);
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/* 2^253 - 2^3 */ fe25519_square(&t1,&t0);
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/* 2^254 - 2^4 */ fe25519_square(&t0,&t1);
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/* 2^255 - 2^5 */ fe25519_square(&t1,&t0);
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/* 2^255 - 21 */ fe25519_mul(r,&t1,&z11);
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}
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