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ECICSDecrypt

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orignal 2017-11-01 10:59:36 -04:00
parent 6d01726961
commit 5271cdacf2
2 changed files with 51 additions and 1 deletions
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50
libi2pd/Crypto.cpp
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@ -410,6 +410,56 @@ namespace crypto
BN_CTX_end (ctx);
}
bool ECICSDecrypt (const EC_GROUP * curve, const BIGNUM * key, const uint8_t * encrypted, uint8_t * data, BN_CTX * ctx)
{
bool ret = true;
BN_CTX_start (ctx);
BIGNUM * q = BN_CTX_get (ctx);
EC_GROUP_get_order(curve, q, ctx);
int len = BN_num_bytes (q);
// point for shared secret
BIGNUM * x = BN_CTX_get (ctx), * y = BN_CTX_get (ctx);
BN_bin2bn (encrypted, len, x);
BN_bin2bn (encrypted + len, len, y);
auto p = EC_POINT_new (curve);
if (EC_POINT_set_affine_coordinates_GFp (curve, p, x, y, nullptr))
{
auto s = EC_POINT_new (curve);
EC_POINT_mul (curve, s, nullptr, p, key, ctx);
EC_POINT_get_affine_coordinates_GFp (curve, s, x, y, nullptr);
EC_POINT_free (s);
uint8_t keyBuf[64], iv[64], shared[32];
bn2buf (x, keyBuf, len);
bn2buf (y, iv, len);
SHA256 (keyBuf, len, shared);
// decrypt
uint8_t m[256];
CBCDecryption decryption;
decryption.SetKey (shared);
decryption.SetIV (iv);
decryption.Decrypt (encrypted + 256, 256, m);
// verify and copy
uint8_t hash[32];
SHA256 (m + 33, 222, hash);
if (!memcmp (m + 1, hash, 32))
memcpy (data, m + 33, 222);
else
{
LogPrint (eLogError, "ECICS decrypt hash doesn't match");
ret = false;
}
}
else
{
LogPrint (eLogError, "ECICS decrypt point is invalid");
ret = false;
}
EC_POINT_free (p);
BN_CTX_end (ctx);
return ret;
}
// HMAC
const uint64_t IPAD = 0x3636363636363636;
const uint64_t OPAD = 0x5C5C5C5C5C5C5C5C;

2
libi2pd/Crypto.h
View File

@ -54,7 +54,7 @@ namespace crypto
// ECICS
void ECICSEncrypt (const EC_GROUP * curve, const EC_POINT * key, const uint8_t * data, uint8_t * encrypted, BN_CTX * ctx); // 222 bytes data, 512 bytes encrypted
bool ECICSDecrypt (const EC_GROUP * curve, const BIGNUM * key, const uint8_t * encrypted, uint8_t * data, BN_CTX * ctx);
// HMAC
typedef i2p::data::Tag<32> MACKey;