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375 lines
7.5 KiB
C
375 lines
7.5 KiB
C
/*
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* Public Domain, Authors: Daniel J. Bernstein, Niels Duif, Tanja Lange,
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* Peter Schwabe, Bo-Yin Yang.
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* Copied from supercop-20130419/crypto_sign/ed25519/ref/sc25519.c
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*/
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#include <stdint.h>
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#include <sxt/sc25519.h>
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/*Arithmetic modulo the group order m = 2^252 + 27742317777372353535851937790883648493 = 7237005577332262213973186563042994240857116359379907606001950938285454250989 */
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static const uint32_t m[32] = {
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0xED, 0xD3, 0xF5, 0x5C, 0x1A, 0x63, 0x12, 0x58,
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0xD6, 0x9C, 0xF7, 0xA2, 0xDE, 0xF9, 0xDE, 0x14,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
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};
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static const uint32_t mu[33] = {
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0x1B, 0x13, 0x2C, 0x0A, 0xA3, 0xE5, 0x9C, 0xED,
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0xA7, 0x29, 0x63, 0x08, 0x5D, 0x21, 0x06, 0x21,
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0xEB, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x0F
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};
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static uint32_t lt(uint32_t a,uint32_t b) /* 16-bit inputs */
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{
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unsigned int x = a;
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x -= (unsigned int) b; /* 0..65535: no; 4294901761..4294967295: yes */
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x >>= 31; /* 0: no; 1: yes */
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return x;
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}
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/* Reduce coefficients of r before calling reduce_add_sub */
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static void reduce_add_sub(sc25519 *r)
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{
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uint32_t pb = 0;
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uint32_t b;
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uint32_t mask;
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int i;
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unsigned char t[32];
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for (i = 0; i < 32; i++) {
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pb += m[i];
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b = lt(r->v[i],pb);
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t[i] = r->v[i]-pb+(b<<8);
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pb = b;
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}
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mask = b - 1;
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for (i = 0; i < 32; i++) {
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r->v[i] ^= mask & (r->v[i] ^ t[i]);
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}
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}
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/* Reduce coefficients of x before calling barrett_reduce */
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static void barrett_reduce(sc25519 *r, const uint32_t x[64])
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{
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/* See HAC, Alg. 14.42 */
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int i,j;
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uint32_t q2[66];
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uint32_t *q3 = q2 + 33;
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uint32_t r1[33];
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uint32_t r2[33];
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uint32_t carry;
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uint32_t pb = 0;
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uint32_t b;
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for (i = 0; i < 66; i++) {
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q2[i] = 0;
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}
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for (i = 0; i < 33; i++) {
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r2[i] = 0;
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}
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for (i = 0; i < 33; i++) {
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for (j = 0; j < 33; j++) {
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if (i + j >= 31) {
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q2[i+j] += mu[i]*x[j+31];
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}
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}
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}
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carry = q2[31] >> 8;
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q2[32] += carry;
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carry = q2[32] >> 8;
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q2[33] += carry;
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for (i = 0; i < 33; i++) {
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r1[i] = x[i];
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}
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for (i = 0; i < 32; i++) {
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for (j = 0; j < 33; j++) {
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if (i + j < 33) {
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r2[i+j] += m[i]*q3[j];
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}
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}
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}
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for (i = 0; i < 32; i++) {
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carry = r2[i] >> 8;
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r2[i+1] += carry;
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r2[i] &= 0xff;
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}
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for (i = 0; i < 32; i++) {
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pb += r2[i];
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b = lt(r1[i],pb);
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r->v[i] = r1[i]-pb+(b<<8);
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pb = b;
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}
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/* XXX: Can it really happen that r<0?, See HAC, Alg 14.42, Step 3
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* If so: Handle it here!
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*/
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reduce_add_sub(r);
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reduce_add_sub(r);
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}
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void sc25519_from32bytes(sc25519 *r, const unsigned char x[32])
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{
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int i;
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uint32_t t[64];
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for (i = 0; i < 32; i++) {
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t[i] = x[i];
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}
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for (i = 32; i < 64; i++) {
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t[i] = 0;
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}
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barrett_reduce(r, t);
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}
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void shortsc25519_from16bytes(shortsc25519 *r, const unsigned char x[16])
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{
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int i;
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for (i = 0; i < 16; i++) {
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r->v[i] = x[i];
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}
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}
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void sc25519_from64bytes(sc25519 *r, const unsigned char x[64])
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{
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int i;
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uint32_t t[64];
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for (i = 0; i < 64; i++) {
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t[i] = x[i];
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}
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barrett_reduce(r, t);
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}
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void sc25519_from_shortsc(sc25519 *r, const shortsc25519 *x)
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{
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int i;
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for (i = 0; i < 16; i++) {
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r->v[i] = x->v[i];
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}
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for (i = 0; i < 16; i++) {
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r->v[16+i] = 0;
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}
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}
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void sc25519_to32bytes(unsigned char r[32], const sc25519 *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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}
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}
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int sc25519_iszero_vartime(const sc25519 *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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if(x->v[i] != 0) {
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return 0;
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}
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}
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return 1;
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}
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int sc25519_isshort_vartime(const sc25519 *x)
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{
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int i;
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for (i = 31; i > 15; i--) {
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if (x->v[i] != 0) {
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return 0;
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}
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}
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return 1;
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}
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int sc25519_lt_vartime(const sc25519 *x, const sc25519 *y)
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{
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int i;
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for (i = 31; i >= 0; i--) {
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if (x->v[i] < y->v[i]) {
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return 1;
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}
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if (x->v[i] > y->v[i]) {
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return 0;
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}
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}
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return 0;
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}
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void sc25519_add(sc25519 *r, const sc25519 *x, const sc25519 *y)
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{
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int i, carry;
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for (i = 0; i < 32; i++) {
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r->v[i] = x->v[i] + y->v[i];
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}
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for (i = 0;i < 31; i++) {
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carry = r->v[i] >> 8;
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r->v[i+1] += carry;
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r->v[i] &= 0xff;
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}
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reduce_add_sub(r);
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}
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void sc25519_sub_nored(sc25519 *r, const sc25519 *x, const sc25519 *y)
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{
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uint32_t b = 0;
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uint32_t t;
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int i;
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for (i = 0; i < 32; i++) {
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t = x->v[i] - y->v[i] - b;
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r->v[i] = t & 255;
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b = (t >> 8) & 1;
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}
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}
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void sc25519_mul(sc25519 *r, const sc25519 *x, const sc25519 *y)
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{
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int i,j,carry;
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uint32_t t[64];
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for (i = 0; i < 64; i++) {
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t[i] = 0;
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}
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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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}
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}
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/* Reduce coefficients */
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for (i = 0; i < 63; i++) {
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carry = t[i] >> 8;
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t[i+1] += carry;
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t[i] &= 0xff;
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}
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barrett_reduce(r, t);
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}
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void sc25519_mul_shortsc(sc25519 *r, const sc25519 *x, const shortsc25519 *y)
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{
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sc25519 t;
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sc25519_from_shortsc(&t, y);
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sc25519_mul(r, x, &t);
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}
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void sc25519_window3(signed char r[85], const sc25519 *s)
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{
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char carry;
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int i;
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for (i = 0; i < 10; i++) {
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r[8*i+0] = s->v[3*i+0] & 7;
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r[8*i+1] = (s->v[3*i+0] >> 3) & 7;
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r[8*i+2] = (s->v[3*i+0] >> 6) & 7;
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r[8*i+2] ^= (s->v[3*i+1] << 2) & 7;
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r[8*i+3] = (s->v[3*i+1] >> 1) & 7;
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r[8*i+4] = (s->v[3*i+1] >> 4) & 7;
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r[8*i+5] = (s->v[3*i+1] >> 7) & 7;
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r[8*i+5] ^= (s->v[3*i+2] << 1) & 7;
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r[8*i+6] = (s->v[3*i+2] >> 2) & 7;
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r[8*i+7] = (s->v[3*i+2] >> 5) & 7;
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}
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r[8*i+0] = s->v[3*i+0] & 7;
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r[8*i+1] = (s->v[3*i+0] >> 3) & 7;
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r[8*i+2] = (s->v[3*i+0] >> 6) & 7;
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r[8*i+2] ^= (s->v[3*i+1] << 2) & 7;
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r[8*i+3] = (s->v[3*i+1] >> 1) & 7;
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r[8*i+4] = (s->v[3*i+1] >> 4) & 7;
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/* Making it signed */
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carry = 0;
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for (i = 0; i < 84; i++) {
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r[i] += carry;
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r[i+1] += r[i] >> 3;
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r[i] &= 7;
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carry = r[i] >> 2;
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r[i] -= carry<<3;
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}
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r[84] += carry;
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}
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void sc25519_window5(signed char r[51], const sc25519 *s)
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{
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char carry;
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int i;
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for (i = 0; i < 6; i++) {
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r[8*i+0] = s->v[5*i+0] & 31;
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r[8*i+1] = (s->v[5*i+0] >> 5) & 31;
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r[8*i+1] ^= (s->v[5*i+1] << 3) & 31;
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r[8*i+2] = (s->v[5*i+1] >> 2) & 31;
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r[8*i+3] = (s->v[5*i+1] >> 7) & 31;
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r[8*i+3] ^= (s->v[5*i+2] << 1) & 31;
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r[8*i+4] = (s->v[5*i+2] >> 4) & 31;
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r[8*i+4] ^= (s->v[5*i+3] << 4) & 31;
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r[8*i+5] = (s->v[5*i+3] >> 1) & 31;
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r[8*i+6] = (s->v[5*i+3] >> 6) & 31;
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r[8*i+6] ^= (s->v[5*i+4] << 2) & 31;
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r[8*i+7] = (s->v[5*i+4] >> 3) & 31;
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}
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r[8*i+0] = s->v[5*i+0] & 31;
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r[8*i+1] = (s->v[5*i+0] >> 5) & 31;
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r[8*i+1] ^= (s->v[5*i+1] << 3) & 31;
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r[8*i+2] = (s->v[5*i+1] >> 2) & 31;
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/* Making it signed */
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carry = 0;
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for (i = 0; i < 50; i++) {
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r[i] += carry;
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r[i+1] += r[i] >> 5;
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r[i] &= 31;
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carry = r[i] >> 4;
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r[i] -= carry<<5;
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}
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r[50] += carry;
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}
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void sc25519_2interleave2(unsigned char r[127],
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const sc25519 *s1,
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const sc25519 *s2)
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{
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int i;
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for (i = 0; i < 31; i++) {
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r[4*i] = ( s1->v[i] & 3) ^ (( s2->v[i] & 3) << 2);
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r[4*i+1] = ((s1->v[i] >> 2) & 3) ^ (((s2->v[i] >> 2) & 3) << 2);
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r[4*i+2] = ((s1->v[i] >> 4) & 3) ^ (((s2->v[i] >> 4) & 3) << 2);
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r[4*i+3] = ((s1->v[i] >> 6) & 3) ^ (((s2->v[i] >> 6) & 3) << 2);
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}
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r[124] = ( s1->v[31] & 3) ^ (( s2->v[31] & 3) << 2);
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r[125] = ((s1->v[31] >> 2) & 3) ^ (((s2->v[31] >> 2) & 3) << 2);
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r[126] = ((s1->v[31] >> 4) & 3) ^ (((s2->v[31] >> 4) & 3) << 2);
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}
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