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#include "ed25519.h"
#include "sha512.h"
#include "ge.h"
#include "sc.h"
static int consttime_equal(const unsigned char *x, const unsigned char *y) {
unsigned char r = 0;
r = x[0] ^ y[0];
#define F(i) r |= x[i] ^ y[i]
F(1);
F(2);
F(3);
F(4);
F(5);
F(6);
F(7);
F(8);
F(9);
F(10);
F(11);
F(12);
F(13);
F(14);
F(15);
F(16);
F(17);
F(18);
F(19);
F(20);
F(21);
F(22);
F(23);
F(24);
F(25);
F(26);
F(27);
F(28);
F(29);
F(30);
F(31);
#undef F
return !r;
}
int ed25519_verify(const unsigned char *signature, const unsigned char *message, size_t message_len, const unsigned char *public_key) {
unsigned char h[64];
unsigned char checker[32];
sha512_context hash;
ge_p3 A;
ge_p2 R;
if (signature[63] & 224) {
return 0;
}
if (ge_frombytes_negate_vartime(&A, public_key) != 0) {
return 0;
}
sha512_init(&hash);
sha512_update(&hash, signature, 32);
sha512_update(&hash, public_key, 32);
sha512_update(&hash, message, message_len);
sha512_final(&hash, h);
sc_reduce(h);
ge_double_scalarmult_vartime(&R, h, &A, signature + 32);
ge_tobytes(checker, &R);
if (!consttime_equal(checker, signature)) {
return 0;
}
return 1;
}
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