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