op_hash160 misimplemented #14
Description
Consider the script 74686973697361736563726574 op_hash160.
Answer expected: 0x835ca4a6a1c2baaaf63bf33c777aff2fc681b017
Answer returned: 0xa69008fd5d7297bed5b71fea578a770e150b2f92
Expected behaviour confirmed at https://www.indicrypto.com/bitcointools/tool/pubkey-to-hash, https://bitcoinprices.org/public-key-to-hash/ and by running through the current master at https://github.com/kallewoof/btcdeb.
The error derives from mishandling the preimages as ascii instead of binary.
In PHP the hash() function returns ascii formed as hexadecimal. Thus:
php > echo hash('ripemd160', hash('sha256', '74686973697361736563726574'));
a69008fd5d7297bed5b71fea578a770e150b2f92
A correct implementation converts the preimages to binary first:
function hexStringToByteString($hexString){
$len=strlen($hexString);
$byteString="";
for ($i=0;$i<$len;$i=$i+2){
$charnum=hexdec(substr($hexString,$i,2));
$byteString.=chr($charnum);
}
return $byteString;
}
function op_hashop160($preimage) {
$preimage1 = hexStringToByteString($preimage);
$hash1 = hash('sha256', $preimage1);
$preimage2 = hexStringToByteString($hash1);
$hash2 = hash('ripemd160', $preimage2);
return $hash2;
}
php > echo op_hashop160('74686973697361736563726574');
835ca4a6a1c2baaaf63bf33c777aff2fc681b017
Thanks!