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simplito / elliptic-php

Fast, general Elliptic Curve Cryptography library. Supports curves used in Bitcoin, Ethereum and other cryptocurrencies (secp256k1, ed25519, ..)
MIT License
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Lib failed comparison agains trusty native Curve25519 #18

Open AsenOsen opened 4 years ago

AsenOsen commented 4 years ago

I`ve decided to compare basic calculation of public key based on private key against Curve25519:

$secureRandom = openssl_random_pseudo_bytes ( 32);
// native curve25519.so
$trusty_private = curve25519_private($secureRandom);
$trusty_public = curve25519_public($trusty_private);

// this library
$ec = new EC('curve25519');
$untrusty_keypair = $ec->keyFromPrivate(bin2hex($trusty_private));
$untrusty_public = $untrusty_keypair->getPublic(true, 'hex');

echo $untrusty_public . PHP_EOL;
echo bin2hex($trusty_public) . PHP_EOL;

and this check has failed:

6aa466621807d91ec5a6777544a6796fde5adf8b72a842b23c25f0c479f3aa71
d323bc8387b836dca1cc42fb8f53cb533ff5eaaf2461adc8ef698640bd614a4b
ldudzsim commented 4 years ago

In ECC public key is a point. In the Montgomery version of curve25519 in our lib we return public key in normalized form, it means that second coordinate is always 1, so only x is returned and it is returned in big endian order and that’s it. When you use the edward version of curve (ed25519) you get a standard formatted public key with the beginning 0x02/0x03 for compact and 0x04 for the full version. I don't know in what form your lib returns the public key, but it does not match with our lib for sure. Finally, I mention that our lib is port of elliptic-js, so you can also compare your lib with it, but the results will be similar.