Mike Hearn pointed me to the relevant comment in bitcoinj.
While adapting the bitcoinj block tester to bitsofproof. I struggle to get the meaning of the following comment:
FullBlocktestGenerator.java (line 715)
// Exploit the SigHash.SINGLE bug to avoid having to make more than one signature
Would you please elaborate? What bug?
I see that the transaction generated has two inputs and only only output e.g.:
Code:
{ "hash" : "1b4ef446fa472102ceac746719776b763dd7738034345f601258a57e00bc91f1",
"inputs" : [ { "script" : "OP_1",
"sequence" : 4294967295,
"sourceHash" : "725c65ff90a83606f33928761603c9d9f07eb521f5c464b1ddc45dda8ead07f7",
"sourceIx" : 2
},
{ "script" : "0x01ac 0x47304402203fde73d126d8e09349e49d5ed17e18e43c85e9a3a56bfd3a0ccd4da891e0e93102203d5f66ab7886e783ddd7d48b16c85a2ff4a4f9fd32c504ad87dc8928a1c7740103 0x2d21022433dcb55ce46f18d3dd17d66893a7670a4bc059f21897a55af959c75b0717c26ead6ead6ead6ead6eadac",
"sequence" : 4294967295,
"sourceHash" : "b13e5c58e43e3bb2c59d0dccddbf4713c142552bdcca5fcfcb851eab3f86703e",
"sourceIx" : 0
}
],
"lockTime" : 0,
"outputs" : [ { "script" : "OP_1",
"value" : 1
} ],
"version" : 1
}
"inputs" : [ { "script" : "OP_1",
"sequence" : 4294967295,
"sourceHash" : "725c65ff90a83606f33928761603c9d9f07eb521f5c464b1ddc45dda8ead07f7",
"sourceIx" : 2
},
{ "script" : "0x01ac 0x47304402203fde73d126d8e09349e49d5ed17e18e43c85e9a3a56bfd3a0ccd4da891e0e93102203d5f66ab7886e783ddd7d48b16c85a2ff4a4f9fd32c504ad87dc8928a1c7740103 0x2d21022433dcb55ce46f18d3dd17d66893a7670a4bc059f21897a55af959c75b0717c26ead6ead6ead6ead6eadac",
"sequence" : 4294967295,
"sourceHash" : "b13e5c58e43e3bb2c59d0dccddbf4713c142552bdcca5fcfcb851eab3f86703e",
"sourceIx" : 0
}
],
"lockTime" : 0,
"outputs" : [ { "script" : "OP_1",
"value" : 1
} ],
"version" : 1
}
Reading the Satoshi code I would assume that this does not evaluate to true for input 1 since:
script.cpp:
Code:
else if ((nHashType & 0x1f) == SIGHASH_SINGLE)
{
// Only lock-in the txout payee at same index as txin
unsigned int nOut = nIn;
if (nOut >= txTmp.vout.size())
{
printf("ERROR: SignatureHash() : nOut=%d out of range\n", nOut);
return 1;
}
{
// Only lock-in the txout payee at same index as txin
unsigned int nOut = nIn;
if (nOut >= txTmp.vout.size())
{
printf("ERROR: SignatureHash() : nOut=%d out of range\n", nOut);
return 1;
}
but apparently it does. Why?