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handle case when encoded key is (p-1)/2

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orignal 2019-12-10 13:40:04 -05:00
parent 4d7b86ca26
commit 36eaaa748c
2 changed files with 14 additions and 1 deletions
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2
libi2pd/Elligator.cpp
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@ -100,7 +100,7 @@ namespace crypto
BIGNUM * r = BN_CTX_get (ctx); BN_bin2bn (encoded1, 32, r); BIGNUM * r = BN_CTX_get (ctx); BN_bin2bn (encoded1, 32, r);
if (BN_cmp (r, p12) < 0) // r < (p-1)/2 if (BN_cmp (r, p12) <= 0) // r < (p-1)/2
{ {
// v = -A/(1+u*r^2) // v = -A/(1+u*r^2)
BIGNUM * v = BN_CTX_get (ctx); BN_mod_sqr (v, r, p, ctx); BIGNUM * v = BN_CTX_get (ctx); BN_mod_sqr (v, r, p, ctx);

13
tests/test-elligator.cpp
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@ -40,6 +40,17 @@ const uint8_t key2[32] =
0xe5, 0x78, 0x2b, 0xe1, 0xe1, 0x14, 0x5c, 0xe2, 0xc3, 0xc6, 0xfd, 0xe1, 0x6d, 0xed, 0x53, 0x63 0xe5, 0x78, 0x2b, 0xe1, 0xe1, 0x14, 0x5c, 0xe2, 0xc3, 0xc6, 0xfd, 0xe1, 0x6d, 0xed, 0x53, 0x63
}; };
const uint8_t encoded3[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
};
const uint8_t key3[32] =
{
0x9c, 0xdb, 0x52, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55
};
int main () int main ()
{ {
@ -53,4 +64,6 @@ int main ()
assert(memcmp (buf, key1, 32) == 0); assert(memcmp (buf, key1, 32) == 0);
el.Decode (encoded2, buf); el.Decode (encoded2, buf);
assert(memcmp (buf, key2, 32) == 0); assert(memcmp (buf, key2, 32) == 0);
el.Decode (encoded3, buf);
assert(memcmp (buf, key3, 32) == 0);
} }