https://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&feed=atom&action=historyZero Knowledge Contingent Payment - Revision history2024-03-28T17:46:07ZRevision history for this page on the wikiMediaWiki 1.30.0https://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=67442&oldid=prevJonathanCross: /* Hash locked transactions */ Its => It's2020-04-08T11:17:08Z<p><span dir="auto"><span class="autocomment">Hash locked transactions: </span> Its => It's</span></p>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del class="diffchange diffchange-inline">Its </del>possible to author a payment in the existing Bitcoin system that requires the redeemer to provide a "secret" which hashes to a specified value. [https://blockexplorer.com/tx/9969603dca74d14d29d1d5f56b94c7872551607f8c2d6837ab9715c60721b50e The 0.01 output here with the SHA256 opcode] is an example of such a transaction.  "To collect these funds your transaction must provide a value that hashes to this other value."</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">It's </ins>possible to author a payment in the existing Bitcoin system that requires the redeemer to provide a "secret" which hashes to a specified value. [https://blockexplorer.com/tx/9969603dca74d14d29d1d5f56b94c7872551607f8c2d6837ab9715c60721b50e The 0.01 output here with the SHA256 opcode] is an example of such a transaction.  "To collect these funds your transaction must provide a value that hashes to this other value."</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Used directly, like in the above example, this is insecure: Once you've published the spending transaction another node could just drop your transaction and use the password in a new transaction that pays him instead.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Used directly, like in the above example, this is insecure: Once you've published the spending transaction another node could just drop your transaction and use the password in a new transaction that pays him instead.</div></td></tr>
</table>JonathanCrosshttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=60497&oldid=prevDooglus: /* Further mproving privacy */ typos2016-02-27T04:06:44Z<p><span dir="auto"><span class="autocomment">Further mproving privacy: </span> typos</span></p>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Alternatively, you could construct the payment as an anyone can pay transaction where the output is greater than the input you provide. You would give him this transaction, then he would add funds of his own and announce it and wait for it to be mined before announcing the key in the transaction spending it. This way he could not lock up your funds without locking up funds of his own.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Alternatively, you could construct the payment as an anyone can pay transaction where the output is greater than the input you provide. You would give him this transaction, then he would add funds of his own and announce it and wait for it to be mined before announcing the key in the transaction spending it. This way he could not lock up your funds without locking up funds of his own.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>==Further <del class="diffchange diffchange-inline">mproving </del>privacy==</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==Further <ins class="diffchange diffchange-inline">improving </ins>privacy==</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Many other transaction types also use the same hash locked pattern, but privacy can be further improved:</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Many other transaction types also use the same hash locked pattern, but privacy can be further improved:</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A ZK-payment can be transformed using the [https://bitcointalk.org/index.php?topic=321228.0 CoinSwap] approach where <del class="diffchange diffchange-inline">they </del>payer first pays into an ordinary 2-of-2 escrow+refund with the payee. <del class="diffchange diffchange-inline">The </del>then would perform the ZK-payment transactions described above externally to the Bitcoin network, and if everything goes through without cheating the payer just signs a 2-of-2 release to pay the payee directly, without disclosing to the network that a hashlocked transaction was used. If the payer fails to release the escrow directly, the payee can just release it by announcing the hashlock and hashlock redeem.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A ZK-payment can be transformed using the [https://bitcointalk.org/index.php?topic=321228.0 CoinSwap] approach where <ins class="diffchange diffchange-inline">the </ins>payer first pays into an ordinary 2-of-2 escrow+refund with the payee. <ins class="diffchange diffchange-inline">They </ins>then would perform the ZK-payment transactions described above externally to the Bitcoin network, and if everything goes through without cheating the payer just signs a 2-of-2 release to pay the payee directly, without disclosing to the network that a hashlocked transaction was used. If the payer fails to release the escrow directly, the payee can just release it by announcing the hashlock and hashlock redeem.</div></td></tr>
</table>Dooglushttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=60496&oldid=prevDooglus: /* Hash locked transactions */ typo2016-02-27T03:59:16Z<p><span dir="auto"><span class="autocomment">Hash locked transactions: </span> typo</span></p>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>So— the advice is that you shouldn't use a password alone, you should require a signature and a password.  But then what is the use of that?</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>So— the advice is that you shouldn't use a password alone, you should require a signature and a password.  But then what is the use of that?</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>There are a couple uses but I'll give an example here of one of the more impressive <del class="diffchange diffchange-inline">and </del>and far-out ones:</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>There are a couple uses but I'll give an example here of one of the more impressive and far-out ones:</div></td></tr>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>===Zero knowledge proof to binding===  </div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>===Zero knowledge proof to binding===  </div></td></tr>
</table>Dooglushttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=60495&oldid=prevGmaxwell at 22:21, 26 February 20162016-02-26T22:21:48Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>You then form a Bitcoin payment which requires both my public key and password K.  In order to redeem this transaction I must disclose K, the key you need to decrypt Ex and give you your solution. So neither of us can cheat, so no trust is required.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>You then form a Bitcoin payment which requires both my public key and password K.  In order to redeem this transaction I must disclose K, the key you need to decrypt Ex and give you your solution. So neither of us can cheat, so no trust is required.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The [https://bitcoincore.org/en/2016/02/26/zero-knowledge-contingent-payments-announcement/ first ZKCP] was performed on the Bitcoin network in 2016, after <del class="diffchange diffchange-inline">a number of </del>years <del class="diffchange diffchange-inline">waiting </del>for sufficiently powerful general purpose ZKPs to become practically available.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The [https://bitcoincore.org/en/2016/02/26/zero-knowledge-contingent-payments-announcement/ first ZKCP] was performed on the Bitcoin network in 2016, after <ins class="diffchange diffchange-inline">waiting almost 5 </ins>years for sufficiently powerful general purpose ZKPs to become practically available.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==But what if they're just anti-social and don't redeem the txn?==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==But what if they're just anti-social and don't redeem the txn?==</div></td></tr>
</table>Gmaxwellhttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=60494&oldid=prevGmaxwell: Finally reality!2016-02-26T21:39:20Z<p>Finally reality!</p>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>You then form a Bitcoin payment which requires both my public key and password K.  In order to redeem this transaction I must disclose K, the key you need to decrypt Ex and give you your solution. So neither of us can cheat, so no trust is required.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>You then form a Bitcoin payment which requires both my public key and password K.  In order to redeem this transaction I must disclose K, the key you need to decrypt Ex and give you your solution. So neither of us can cheat, so no trust is required.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The <del class="diffchange diffchange-inline">reason this isn't something people are using yet is because while the academics have proven it to be possible, actually converting complicated programs like compositions of ciphers and hash-functions into zero-knowledge proofs with useful levels of performance currently requires toolkits that are not yet publicly available. However, the </del>[<del class="diffchange diffchange-inline">http</del>://<del class="diffchange diffchange-inline">scipr-lab</del>.org/ <del class="diffchange diffchange-inline">SCIPR Lab team] have claimed they will open source their software some time in 2014. "[http:</del>//<del class="diffchange diffchange-inline">eccc.hpi-web.de</del>/<del class="diffchange diffchange-inline">report</del>/<del class="diffchange diffchange-inline">2013/165</del>/<del class="diffchange diffchange-inline">download/ Verifying computations without reexecuting them: from theoretical possibility to near practicality</del>]<del class="diffchange diffchange-inline">" is </del>a <del class="diffchange diffchange-inline">good paper that gives an overview </del>of <del class="diffchange diffchange-inline">progress fo far</del>.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The [<ins class="diffchange diffchange-inline">https</ins>://<ins class="diffchange diffchange-inline">bitcoincore</ins>.org/<ins class="diffchange diffchange-inline">en</ins>/<ins class="diffchange diffchange-inline">2016</ins>/<ins class="diffchange diffchange-inline">02</ins>/<ins class="diffchange diffchange-inline">26</ins>/<ins class="diffchange diffchange-inline">zero-knowledge-contingent-payments-announcement</ins>/ <ins class="diffchange diffchange-inline">first ZKCP</ins>] <ins class="diffchange diffchange-inline">was performed on the Bitcoin network in 2016, after </ins>a <ins class="diffchange diffchange-inline">number </ins>of <ins class="diffchange diffchange-inline">years waiting for sufficiently powerful general purpose ZKPs to become practically available</ins>.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==But what if they're just anti-social and don't redeem the txn?==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==But what if they're just anti-social and don't redeem the txn?==</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l55" >Line 55:</td>
<td colspan="2" class="diff-lineno">Line 55:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Alternatively, you could construct the payment as an anyone can pay transaction where the output is greater than the input you provide. You would give him this transaction, then he would add funds of his own and announce it and wait for it to be mined before announcing the key in the transaction spending it. This way he could not lock up your funds without locking up funds of his own.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Alternatively, you could construct the payment as an anyone can pay transaction where the output is greater than the input you provide. You would give him this transaction, then he would add funds of his own and announce it and wait for it to be mined before announcing the key in the transaction spending it. This way he could not lock up your funds without locking up funds of his own.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>==<del class="diffchange diffchange-inline">Improving </del>privacy==</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==<ins class="diffchange diffchange-inline">Further mproving </ins>privacy==</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">Many other transaction types also use the same hash locked pattern, but privacy can be further improved:</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>A ZK-payment can be transformed using the [https://bitcointalk.org/index.php?topic=321228.0 CoinSwap] approach where they payer first pays into an ordinary 2-of-2 escrow+refund with the payee. The then would perform the ZK-payment transactions described above externally to the Bitcoin network, and if everything goes through without cheating the payer just signs a 2-of-2 release to pay the payee directly, without disclosing to the network that a hashlocked transaction was used. If the payer fails to release the escrow directly, the payee can just release it by announcing the hashlock and hashlock redeem.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>A ZK-payment can be transformed using the [https://bitcointalk.org/index.php?topic=321228.0 CoinSwap] approach where they payer first pays into an ordinary 2-of-2 escrow+refund with the payee. The then would perform the ZK-payment transactions described above externally to the Bitcoin network, and if everything goes through without cheating the payer just signs a 2-of-2 release to pay the payee directly, without disclosing to the network that a hashlocked transaction was used. If the payer fails to release the escrow directly, the payee can just release it by announcing the hashlock and hashlock redeem.</div></td></tr>
</table>Gmaxwellhttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=47093&oldid=prevMike: /* Zero knowledge proof to binding */ fix link2014-05-07T13:15:09Z<p><span dir="auto"><span class="autocomment">Zero knowledge proof to binding: </span> fix link</span></p>
<table class="diff diff-contentalign-left" data-mw="interface">
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<col class="diff-marker" />
<col class="diff-content" />
<tr style="vertical-align: top;" lang="en">
<td colspan="2" style="background-color: white; color:black; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 13:15, 7 May 2014</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l23" >Line 23:</td>
<td colspan="2" class="diff-lineno">Line 23:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>* H() could be a password hashing algorithm and you're looking for the password that gives you a particular hash in order to crack it.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>* H() could be a password hashing algorithm and you're looking for the password that gives you a particular hash in order to crack it.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>* Perhaps H() is a complicated program that decides if a piece of music is one you would find beautiful (i.e. Y is a true/false output)</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>* Perhaps H() is a complicated program that decides if a piece of music is one you would find beautiful (i.e. Y is a true/false output)</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>* H() could be a program that verifies possession of a valid [http://en.wikipedia.org/wiki/<del class="diffchange diffchange-inline">Machine-readable_passport </del>machine readable travel document] issued to a particular person. In this case, you would be able to define a payment to someone based on some arbitrary attributes about them, such as their name + date of birth, or perhaps by providing a photo of their face that's then matched against the travel document using the Eigenfaces algorithm. There would be no need to obtain a public key from them ahead of time meaning that, for example, you could send money to someone who was only just born and doesn't yet have a wallet.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>* H() could be a program that verifies possession of a valid [http://en.wikipedia.org/wiki/<ins class="diffchange diffchange-inline">Biometric_passport </ins>machine readable travel document] issued to a particular person. In this case, you would be able to define a payment to someone based on some arbitrary attributes about them, such as their name + date of birth, or perhaps by providing a photo of their face that's then matched against the travel document using the Eigenfaces algorithm. There would be no need to obtain a public key from them ahead of time meaning that, for example, you could send money to someone who was only just born and doesn't yet have a wallet.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>* H() could be a program that interprets another program on some secret input and yields true if the input data manages to put the program into a corrupted state. This would allow security researchers to sell exploits to software developers so they can be fixed, but in an anonymous and low trust way.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>* H() could be a program that interprets another program on some secret input and yields true if the input data manages to put the program into a corrupted state. This would allow security researchers to sell exploits to software developers so they can be fixed, but in an anonymous and low trust way.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
</table>Mikehttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=47092&oldid=prevMike: /* Zero knowledge proof to binding */ Add more examples of what H() could be. Fold practicality update at the end of the page into main text.2014-05-07T13:13:49Z<p><span dir="auto"><span class="autocomment">Zero knowledge proof to binding: </span> Add more examples of what H() could be. Fold practicality update at the end of the page into main text.</span></p>
<table class="diff diff-contentalign-left" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr style="vertical-align: top;" lang="en">
<td colspan="2" style="background-color: white; color:black; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 13:13, 7 May 2014</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l17" >Line 17:</td>
<td colspan="2" class="diff-lineno">Line 17:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Let H() be a complicated computer program. For some H(X)=Y you want to know some X that gives you a particular Y.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Let H() be a complicated computer program. For some H(X)=Y you want to know some X that gives you a particular Y.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del class="diffchange diffchange-inline">Perhaps H() is a password hashing algorithm </del>and <del class="diffchange diffchange-inline">you</del>'<del class="diffchange diffchange-inline">re looking for the password that gives you a particular hash in order </del>to <del class="diffchange diffchange-inline">crack </del>it<del class="diffchange diffchange-inline">. Or perhaps H() is a complicated program that decides if a image is one </del>you <del class="diffchange diffchange-inline">would find beautiful (e</del>.<del class="diffchange diffchange-inline">g</del>. <del class="diffchange diffchange-inline">Y is either </del>zero <del class="diffchange diffchange-inline">or one, and you want some X where Y==1)</del>.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">Say I happen to _know_ some X that answers your question... </ins>and <ins class="diffchange diffchange-inline">I</ins>'<ins class="diffchange diffchange-inline">d like </ins>to <ins class="diffchange diffchange-inline">sell </ins>it <ins class="diffchange diffchange-inline">to </ins>you. <ins class="diffchange diffchange-inline">But we don't trust each other at all, and because we're computer geeks we have no friends who can act as trusted mediators</ins>. <ins class="diffchange diffchange-inline">Can we make this exchange using Bitcoin with </ins>zero <ins class="diffchange diffchange-inline">trust?  The answer turns out to be yes</ins>.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del class="diffchange diffchange-inline">Say I happen to _know_ </del>some <del class="diffchange diffchange-inline">X that answers your question... and I'd like to sell it to you. But we don't trust each other at all, and because we're computer geeks we have no friends who can act as trusted mediators. Can we make this exchange using Bitcoin with zero trust?  Yes.</del></div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">Here are </ins>some <ins class="diffchange diffchange-inline">examples of what H() could be:</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A [https://en.wikipedia.org/wiki/Zero-knowledge_proof zero-knowledge proof] lets someone prove a mathematical fact to another person without teaching them anything about the fact itself. It has been proven that you can convert any computer program into a zero-knowledge proof(<del class="diffchange diffchange-inline">e.g. </del>[http://en.wikipedia.org/wiki/IP_%28complexity%29#PSPACE_is_a_subset_of_IP PSPACE⊂IP] <!-- IIRC there is a better more direct statement about this someplace but I forget what to look for, please provide a better link -->).  So, using a zero-knowledge proof I could prove to you that I know some X such that H(X)=Y ... which is helpful but it's not enough because you could pay me and I could not tell you the answer (or I could tell you and then you don't pay). Here is where the password locked transactions come in.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">* H() could be a password hashing algorithm and you're looking for the password that gives you a particular hash in order to crack it.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">* Perhaps H() is a complicated program that decides if a piece of music is one you would find beautiful (i.e. Y is a true/false output)</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">* H() could be a program that verifies possession of a valid [http://en.wikipedia.org/wiki/Machine-readable_passport machine readable travel document] issued to a particular person. In this case, you would be able to define a payment to someone based on some arbitrary attributes about them, such as their name + date of birth, or perhaps by providing a photo of their face that's then matched against the travel document using the Eigenfaces algorithm. There would be no need to obtain a public key from them ahead of time meaning that, for example, you could send money to someone who was only just born and doesn't yet have a wallet.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">* H() could be a program that interprets another program on some secret input and yields true if the input data manages to put the program into a corrupted state. This would allow security researchers to sell exploits to software developers so they can be fixed, but in an anonymous and low trust way.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A [https://en.wikipedia.org/wiki/Zero-knowledge_proof zero-knowledge proof] lets someone prove a mathematical fact to another person without teaching them anything about the fact itself. It has been proven that you can convert any computer program into a zero-knowledge proof (<ins class="diffchange diffchange-inline">this is referred to mathematically as </ins>[http://en.wikipedia.org/wiki/IP_%28complexity%29#PSPACE_is_a_subset_of_IP PSPACE⊂IP] <!-- IIRC there is a better more direct statement about this someplace but I forget what to look for, please provide a better link -->).  So, using a zero-knowledge proof I could prove to you that I know some X such that H(X)=Y ... which is helpful but it's not enough because you could pay me and I could not tell you the answer (or I could tell you and then you don't pay). Here is where the password locked transactions come in.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>First I encrypt X with random key K, Ex=AES(X,K).</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>First I encrypt X with random key K, Ex=AES(X,K).</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l40" >Line 40:</td>
<td colspan="2" class="diff-lineno">Line 45:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>You then form a Bitcoin payment which requires both my public key and password K.  In order to redeem this transaction I must disclose K, the key you need to decrypt Ex and give you your solution. So neither of us can cheat, so no trust is required.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>You then form a Bitcoin payment which requires both my public key and password K.  In order to redeem this transaction I must disclose K, the key you need to decrypt Ex and give you your solution. So neither of us can cheat, so no trust is required.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The reason this isn't something people are using yet is because while the academics have proven it to be possible actually converting complicated programs like compositions of ciphers and hash-functions into zero-knowledge proofs <del class="diffchange diffchange-inline">is apparently </del>not <del class="diffchange diffchange-inline">something anyone has figured out how to do practically</del>.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The reason this isn't something people are using yet is because while the academics have proven it to be possible<ins class="diffchange diffchange-inline">, </ins>actually converting complicated programs like compositions of ciphers and hash-functions into zero-knowledge proofs <ins class="diffchange diffchange-inline">with useful levels of performance currently requires toolkits that are </ins>not <ins class="diffchange diffchange-inline">yet publicly available</ins>. <ins class="diffchange diffchange-inline">However, the </ins>[http://scipr-lab.org/ <ins class="diffchange diffchange-inline">SCIPR Lab team</ins>] <ins class="diffchange diffchange-inline">have claimed they will open source their software some time in 2014</ins>. "[http://eccc.hpi-web.de/report/2013/165/download/ Verifying computations without reexecuting them: from theoretical possibility to near practicality]" <ins class="diffchange diffchange-inline">is </ins>a good <ins class="diffchange diffchange-inline">paper that gives an </ins>overview of progress <ins class="diffchange diffchange-inline">fo far</ins>.</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div> </div></td><td colspan="2"> </td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del class="diffchange diffchange-inline">''2013 Update'': This is rapidly changing and </del>[http://scipr-lab.org/ <del class="diffchange diffchange-inline">practical systems</del>] <del class="diffchange diffchange-inline">now appear practically possible</del>. "[http://eccc.hpi-web.de/report/2013/165/download/ Verifying computations without reexecuting them: from theoretical possibility to near practicality]" <del class="diffchange diffchange-inline">gives </del>a good overview<del class="diffchange diffchange-inline">, </del>of <del class="diffchange diffchange-inline">recent </del>progress.</div></td><td colspan="2"> </td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==But what if they're just anti-social and don't redeem the txn?==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==But what if they're just anti-social and don't redeem the txn?==</div></td></tr>
</table>Mikehttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=42873&oldid=prevGmaxwell: /* Zero knowledge proof to binding */ survey link2013-12-04T18:21:20Z<p><span dir="auto"><span class="autocomment">Zero knowledge proof to binding: </span> survey link</span></p>
<table class="diff diff-contentalign-left" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr style="vertical-align: top;" lang="en">
<td colspan="2" style="background-color: white; color:black; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 18:21, 4 December 2013</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l40" >Line 40:</td>
<td colspan="2" class="diff-lineno">Line 40:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>You then form a Bitcoin payment which requires both my public key and password K.  In order to redeem this transaction I must disclose K, the key you need to decrypt Ex and give you your solution. So neither of us can cheat, so no trust is required.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>You then form a Bitcoin payment which requires both my public key and password K.  In order to redeem this transaction I must disclose K, the key you need to decrypt Ex and give you your solution. So neither of us can cheat, so no trust is required.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The reason this isn't something people are using yet is because while the academics have proven it to be possible actually converting complicated programs like compositions of ciphers and hash-functions into zero-knowledge proofs is apparently not something anyone has figured out how to do practically. ''2013 Update'': This is rapidly changing and [http://scipr-lab.org/ practical systems] now appear practically possible.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The reason this isn't something people are using yet is because while the academics have proven it to be possible actually converting complicated programs like compositions of ciphers and hash-functions into zero-knowledge proofs is apparently not something anyone has figured out how to do practically.</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>''2013 Update'': This is rapidly changing and [http://scipr-lab.org/ practical systems] now appear practically possible<ins class="diffchange diffchange-inline">. "[http://eccc.hpi-web.de/report/2013/165/download/ Verifying computations without reexecuting them: from theoretical possibility to near practicality]" gives a good overview, of recent progress</ins>.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==But what if they're just anti-social and don't redeem the txn?==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==But what if they're just anti-social and don't redeem the txn?==</div></td></tr>
</table>Gmaxwellhttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=42871&oldid=prevMike: /* Zero nowledge proof to binding */2013-12-04T16:03:10Z<p><span dir="auto"><span class="autocomment">Zero nowledge proof to binding</span></span></p>
<table class="diff diff-contentalign-left" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr style="vertical-align: top;" lang="en">
<td colspan="2" style="background-color: white; color:black; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 16:03, 4 December 2013</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l13" >Line 13:</td>
<td colspan="2" class="diff-lineno">Line 13:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>There are a couple uses but I'll give an example here of one of the more impressive and and far-out ones:</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>There are a couple uses but I'll give an example here of one of the more impressive and and far-out ones:</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>===Zero <del class="diffchange diffchange-inline">nowledge </del>proof to binding===  </div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>===Zero <ins class="diffchange diffchange-inline">knowledge </ins>proof to binding===  </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Let H() be a complicated computer program. For some H(X)=Y you want to know some X that gives you a particular Y.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Let H() be a complicated computer program. For some H(X)=Y you want to know some X that gives you a particular Y.</div></td></tr>
</table>Mikehttps://en.bitcoin.it/w/index.php?title=Zero_Knowledge_Contingent_Payment&diff=42870&oldid=prevGmaxwell: spelling2013-12-04T15:48:22Z<p>spelling</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr style="vertical-align: top;" lang="en">
<td colspan="2" style="background-color: white; color:black; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: white; color:black; text-align: center;">Revision as of 15:48, 4 December 2013</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >Line 1:</td>
<td colspan="2" class="diff-lineno">Line 1:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>It's possible to make payments using Bitcoin which are released if and only if some <del class="diffchange diffchange-inline">knoweldge </del>is disclosed by the payee and to do this in a trustless manner where neither the payer or payee can cheat. This is accomplished using the combination of a hash-locked transaction and a bitcoin-external protocol to set things up so that the data revealed in the hashlock release is the data they need.</div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>It's possible to make payments using Bitcoin which are released if and only if some <ins class="diffchange diffchange-inline">knowledge </ins>is disclosed by the payee and to do this in a trustless manner where neither the payer or payee can cheat. This is accomplished using the combination of a hash-locked transaction and a bitcoin-external protocol to set things up so that the data revealed in the hashlock release is the data they need.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==Protocol outline==</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>==Protocol outline==</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l13" >Line 13:</td>
<td colspan="2" class="diff-lineno">Line 13:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>There are a couple uses but I'll give an example here of one of the more impressive and and far-out ones:</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>There are a couple uses but I'll give an example here of one of the more impressive and and far-out ones:</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>===Zero <del class="diffchange diffchange-inline">knoweldge </del>proof to binding===  </div></td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>===Zero <ins class="diffchange diffchange-inline">nowledge </ins>proof to binding===  </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Let H() be a complicated computer program. For some H(X)=Y you want to know some X that gives you a particular Y.</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>Let H() be a complicated computer program. For some H(X)=Y you want to know some X that gives you a particular Y.</div></td></tr>
</table>Gmaxwell