Add crypto_core_curve25519_is_valid_point()
This commit is contained in:
Frank Denis
parent
933b3e8ec1
commit
2a031b95ff
@ -164,6 +164,7 @@ if !MINIMAL
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libsodium_la_SOURCES += \
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crypto_box/curve25519xchacha20poly1305/box_curve25519xchacha20poly1305.c \
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crypto_box/curve25519xchacha20poly1305/box_seal_curve25519xchacha20poly1305.c \
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crypto_core/curve25519/core_curve25519.c \
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crypto_core/ed25519/core_ed25519.c \
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crypto_pwhash/scryptsalsa208sha256/crypto_scrypt-common.c \
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crypto_pwhash/scryptsalsa208sha256/crypto_scrypt.h \
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222
src/libsodium/crypto_core/curve25519/core_curve25519.c
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222
src/libsodium/crypto_core/curve25519/core_curve25519.c
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@ -0,0 +1,222 @@
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#include <stdio.h>
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#include "crypto_core_curve25519.h"
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#include "crypto_core_ed25519.h"
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#include "crypto_scalarmult_curve25519.h"
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#include "export.h"
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#include "private/common.h"
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#include "private/ed25519_ref10.h"
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#ifdef HAVE_TI_MODE
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# include "../ed25519/ref10/fe_51/constants.h"
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#else
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# include "../ed25519/ref10/fe_25_5/constants.h"
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#endif
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static int
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is_canonical(const unsigned char *s)
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{
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unsigned char c;
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unsigned char d;
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unsigned int i;
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c = s[31] ^ 0x7f;
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for (i = 30; i > 0; i--) {
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c |= s[i] ^ 0xff;
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}
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c = (((unsigned int) c) - 1U) >> 8;
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d = (0xed - 1U - (unsigned int) s[0]) >> 8;
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return 1 - (c & d & 1);
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}
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static int
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has_small_order(const unsigned char s[32])
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{
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CRYPTO_ALIGN(16)
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static const unsigned char blacklist[][32] = {
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{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
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{ 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
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{ 0xe0, 0xeb, 0x7a, 0x7c, 0x3b, 0x41, 0xb8, 0xae, 0x16, 0x56, 0xe3, 0xfa, 0xf1, 0x9f, 0xc4, 0x6a, 0xda, 0x09, 0x8d, 0xeb, 0x9c, 0x32, 0xb1, 0xfd, 0x86, 0x62, 0x05, 0x16, 0x5f, 0x49, 0xb8, 0x00 },
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{ 0x5f, 0x9c, 0x95, 0xbc, 0xa3, 0x50, 0x8c, 0x24, 0xb1, 0xd0, 0xb1, 0x55, 0x9c, 0x83, 0xef, 0x5b, 0x04, 0x44, 0x5c, 0xc4, 0x58, 0x1c, 0x8e, 0x86, 0xd8, 0x22, 0x4e, 0xdd, 0xd0, 0x9f, 0x11, 0x57 },
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{ 0xec, 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, 0x7f },
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{ 0xed, 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, 0x7f },
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{ 0xee, 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, 0x7f },
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{ 0xcd, 0xeb, 0x7a, 0x7c, 0x3b, 0x41, 0xb8, 0xae, 0x16, 0x56, 0xe3, 0xfa, 0xf1, 0x9f, 0xc4, 0x6a, 0xda, 0x09, 0x8d, 0xeb, 0x9c, 0x32, 0xb1, 0xfd, 0x86, 0x62, 0x05, 0x16, 0x5f, 0x49, 0xb8, 0x80 },
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{ 0x4c, 0x9c, 0x95, 0xbc, 0xa3, 0x50, 0x8c, 0x24, 0xb1, 0xd0, 0xb1, 0x55, 0x9c, 0x83, 0xef, 0x5b, 0x04, 0x44, 0x5c, 0xc4, 0x58, 0x1c, 0x8e, 0x86, 0xd8, 0x22, 0x4e, 0xdd, 0xd0, 0x9f, 0x11, 0xd7 },
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{ 0xd9, 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, 0xff },
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{ 0xda, 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, 0xff },
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{ 0xdb, 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, 0xff }
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};
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unsigned char c[12] = { 0 };
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unsigned int k;
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size_t i, j;
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COMPILER_ASSERT(12 == sizeof blacklist / sizeof blacklist[0]);
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for (j = 0; j < 32; j++) {
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for (i = 0; i < sizeof blacklist / sizeof blacklist[0]; i++) {
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c[i] |= s[j] ^ blacklist[i][j];
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}
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}
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k = 0;
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for (i = 0; i < sizeof blacklist / sizeof blacklist[0]; i++) {
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k |= (c[i] - 1);
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}
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return (int) ((k >> 8) & 1);
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}
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static void
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fe25519_pow22523(fe25519 out, const fe25519 z)
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{
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fe25519 t0;
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fe25519 t1;
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fe25519 t2;
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int i;
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fe25519_sq(t0, z);
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fe25519_sq(t1, t0);
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fe25519_sq(t1, t1);
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fe25519_mul(t1, z, t1);
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fe25519_mul(t0, t0, t1);
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fe25519_sq(t0, t0);
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fe25519_mul(t0, t1, t0);
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fe25519_sq(t1, t0);
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for (i = 1; i < 5; ++i) {
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fe25519_sq(t1, t1);
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}
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fe25519_mul(t0, t1, t0);
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fe25519_sq(t1, t0);
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for (i = 1; i < 10; ++i) {
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fe25519_sq(t1, t1);
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}
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fe25519_mul(t1, t1, t0);
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fe25519_sq(t2, t1);
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for (i = 1; i < 20; ++i) {
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fe25519_sq(t2, t2);
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}
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fe25519_mul(t1, t2, t1);
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fe25519_sq(t1, t1);
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for (i = 1; i < 10; ++i) {
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fe25519_sq(t1, t1);
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}
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fe25519_mul(t0, t1, t0);
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fe25519_sq(t1, t0);
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for (i = 1; i < 50; ++i) {
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fe25519_sq(t1, t1);
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}
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fe25519_mul(t1, t1, t0);
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fe25519_sq(t2, t1);
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for (i = 1; i < 100; ++i) {
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fe25519_sq(t2, t2);
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}
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fe25519_mul(t1, t2, t1);
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fe25519_sq(t1, t1);
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for (i = 1; i < 50; ++i) {
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fe25519_sq(t1, t1);
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}
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fe25519_mul(t0, t1, t0);
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fe25519_sq(t0, t0);
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fe25519_sq(t0, t0);
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fe25519_mul(out, t0, z);
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}
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static int
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is_on_main_subgroup(const fe25519 x1)
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{
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static const unsigned char L[32] = {
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0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58, 0xd6, 0x9c, 0xf7,
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0xa2, 0xde, 0xf9, 0xde, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
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};
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fe25519 x2;
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fe25519 z2;
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fe25519 x3;
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fe25519 z3;
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fe25519 tmp0;
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fe25519 tmp1;
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int pos;
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unsigned int swap;
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unsigned int b;
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fe25519_1(x2);
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fe25519_0(z2);
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fe25519_copy(x3, x1);
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fe25519_1(z3);
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swap = 0;
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for (pos = 252; pos >= 0; --pos) {
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b = L[pos / 8] >> (pos & 7);
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b &= 1;
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swap ^= b;
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fe25519_cswap(x2, x3, swap);
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fe25519_cswap(z2, z3, swap);
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swap = b;
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fe25519_sub(tmp0, x3, z3);
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fe25519_sub(tmp1, x2, z2);
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fe25519_add(x2, x2, z2);
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fe25519_add(z2, x3, z3);
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fe25519_mul(z3, tmp0, x2);
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fe25519_mul(z2, z2, tmp1);
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fe25519_sq(tmp0, tmp1);
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fe25519_sq(tmp1, x2);
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fe25519_add(x3, z3, z2);
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fe25519_sub(z2, z3, z2);
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fe25519_mul(x2, tmp1, tmp0);
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fe25519_sub(tmp1, tmp1, tmp0);
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fe25519_sq(z2, z2);
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fe25519_scalar_product(z3, tmp1, 121666);
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fe25519_sq(x3, x3);
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fe25519_add(tmp0, tmp0, z3);
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fe25519_mul(z3, x1, z2);
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fe25519_mul(z2, tmp1, tmp0);
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}
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fe25519_cswap(x2, x3, swap);
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fe25519_cswap(z2, z3, swap);
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fe25519_invert(z2, z2);
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fe25519_mul(x2, x2, z2);
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return fe25519_iszero(x2);
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}
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int
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crypto_core_curve25519_is_valid_point(const unsigned char *p)
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{
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fe25519 t;
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fe25519 x;
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fe25519 x2;
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fe25519 Ax;
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fe25519 one;
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fe25519 x2_Ax_1;
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fe25519 y2;
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if (is_canonical(p) == 0 || has_small_order(p) != 0) {
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return 0;
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}
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/* y2 = x3 + Ax2 + x = x(x2 + Ax + 1) */
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fe25519_frombytes(x, p);
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fe25519_sq(x2, x);
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fe25519_mul(Ax, curve25519_A, x);
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fe25519_1(one);
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fe25519_add(x2_Ax_1, x2, Ax);
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fe25519_add(x2_Ax_1, x2_Ax_1, one);
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fe25519_mul(y2, x, x2_Ax_1);
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/* Legendre symbol */
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fe25519_pow22523(t, y2);
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fe25519_sq(t, t);
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fe25519_sq(t, t);
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fe25519_mul(t, t, y2);
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fe25519_mul(t, t, y2);
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/* No roots if the legendre symbol is not 1 */
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if (fe25519_isnegative(t) == 0) {
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return 0;
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}
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/* Multiply by the group order, check that the result is the point at infinity */
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if (is_on_main_subgroup(x) == 0) {
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return 0;
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}
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return 1;
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}
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@ -12,6 +12,7 @@ SODIUM_EXPORT = \
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sodium/crypto_box.h \
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sodium/crypto_box_curve25519xchacha20poly1305.h \
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sodium/crypto_box_curve25519xsalsa20poly1305.h \
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sodium/crypto_core_curve25519.h \
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sodium/crypto_core_ed25519.h \
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sodium/crypto_core_hchacha20.h \
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sodium/crypto_core_hsalsa20.h \
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@ -58,6 +58,7 @@
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#ifndef SODIUM_LIBRARY_MINIMAL
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# include "sodium/crypto_box_curve25519xchacha20poly1305.h"
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# include "sodium/crypto_core_curve25519.h"
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# include "sodium/crypto_core_ed25519.h"
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# include "sodium/crypto_scalarmult_ed25519.h"
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# include "sodium/crypto_secretbox_xchacha20poly1305.h"
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18
src/libsodium/include/sodium/crypto_core_curve25519.h
Normal file
18
src/libsodium/include/sodium/crypto_core_curve25519.h
Normal file
@ -0,0 +1,18 @@
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#ifndef crypto_core_curve25519_H
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#define crypto_core_curve25519_H
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#include <stddef.h>
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#include "export.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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SODIUM_EXPORT
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int crypto_core_curve25519_is_valid_point(const unsigned char *p);
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#ifdef __cplusplus
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}
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#endif
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#endif
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