📅 Original date posted:2016-09-23
📝 Original message:Joe sends Alice 5 BTC (UTXO 0).
Fred sends Alice 4 BTC (UTXO 1).
Alice sends Bob 4 BTC using UTXO 1 (creating UTXO 2).
Fred double-spends UTXO 1 with UTXO 1-B. This invalidates Alice's transfer to
Bob.
Alice has UTXO 0 which she can send to Bob (UTXO 3), but if she does so, it is
possible that UTXO 0 could be mined, and then both UTXO 2 and UTXO 3 which
would result in her giving Bob a total of 8 BTC rather than merely 4 BTC.
Even if Alice waits until Fred's UTXO 1-B confirms 10 blocks deep, it is not
impossible for a reorganization to reverse those 10 blocks and confirm UTXO 1
again.
Using OP_CHECKBLOCKATHEIGHT, however, Alice can create UTXO 3 such that it is
valid only in the blockchain where Fred's UTXO 1-B has confirmed. This way, if
that block is reorganized out, UTXO 3 is invalid, and either Bob receives only
the original UTXO 2, or Alice can create a UTXO 3-B which is valid in the
reorganized blockchain if it again confirms the UTXO 1-B double-spend.
Luke
On Friday, September 23, 2016 2:37:39 PM Tom via bitcoin-dev wrote:
> On Friday 23 Sep 2016 09:57:01 Luke Dashjr via bitcoin-dev wrote:
> > This BIP describes a new opcode (OP_CHECKBLOCKATHEIGHT) for the Bitcoin
> > scripting system to address reissuing bitcoin transactions when the coins
> > they spend have been conflicted/double-spent.
> >
> > https://github.com/luke-jr/bips/blob/bip-cbah/bip-cbah.mediawiki
>
> Can you walk us through a real live usecase which this solves? I read it
> and I think I understand it, but I can't see the attack every giving the
> attacker any benefit (or the attacked losing anything).
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Luke Dashjr [ARCHIVE] /
npub1tf…rfq0n
2023-06-07 19:53:35
in reply to nevent1q…5mfx
Author Public Key
npub1tfk373zg9dnmtvxnpnq7s2dkdgj37rwfj3yrwld7830qltmv8qps8rfq0nPublished at
2023-06-07 19:53:35Event JSON
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"content": "📅 Original date posted:2016-09-23\n📝 Original message:Joe sends Alice 5 BTC (UTXO 0).\nFred sends Alice 4 BTC (UTXO 1).\nAlice sends Bob 4 BTC using UTXO 1 (creating UTXO 2).\nFred double-spends UTXO 1 with UTXO 1-B. This invalidates Alice's transfer to \nBob.\nAlice has UTXO 0 which she can send to Bob (UTXO 3), but if she does so, it is \npossible that UTXO 0 could be mined, and then both UTXO 2 and UTXO 3 which \nwould result in her giving Bob a total of 8 BTC rather than merely 4 BTC.\nEven if Alice waits until Fred's UTXO 1-B confirms 10 blocks deep, it is not \nimpossible for a reorganization to reverse those 10 blocks and confirm UTXO 1 \nagain.\nUsing OP_CHECKBLOCKATHEIGHT, however, Alice can create UTXO 3 such that it is \nvalid only in the blockchain where Fred's UTXO 1-B has confirmed. This way, if \nthat block is reorganized out, UTXO 3 is invalid, and either Bob receives only \nthe original UTXO 2, or Alice can create a UTXO 3-B which is valid in the \nreorganized blockchain if it again confirms the UTXO 1-B double-spend.\n\nLuke\n\nOn Friday, September 23, 2016 2:37:39 PM Tom via bitcoin-dev wrote:\n\u003e On Friday 23 Sep 2016 09:57:01 Luke Dashjr via bitcoin-dev wrote:\n\u003e \u003e This BIP describes a new opcode (OP_CHECKBLOCKATHEIGHT) for the Bitcoin\n\u003e \u003e scripting system to address reissuing bitcoin transactions when the coins\n\u003e \u003e they spend have been conflicted/double-spent.\n\u003e \u003e \n\u003e \u003e https://github.com/luke-jr/bips/blob/bip-cbah/bip-cbah.mediawiki\n\u003e \n\u003e Can you walk us through a real live usecase which this solves? I read it\n\u003e and I think I understand it, but I can't see the attack every giving the\n\u003e attacker any benefit (or the attacked losing anything).\n\u003e _______________________________________________\n\u003e bitcoin-dev mailing list\n\u003e bitcoin-dev at lists.linuxfoundation.org\n\u003e https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev",
"sig": "e6450b9f3ba908548aa155cf504e94ed31c84f13875a6c5535bf29b431039e017a7bd07525d3a8a8a9f902c44bb20246f625b37e95d6cb06b8b2a8d5e76ba7e6"
}