<div dir="ltr"><div class="gmail_quote"><div dir="ltr">Taking the hash of the secret would then require an extra step to make sure the hash is valid for secp256k1.<br><br>Using the x value directly avoids the need for that check.</div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Apr 24, 2015 at 10:35 PM, Patrick Mccorry (PGR) <span dir="ltr">&lt;<a href="mailto:patrick.mccorry@newcastle.ac.uk" target="_blank">patrick.mccorry@newcastle.ac.uk</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">



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<div>When computing the diffie Hellman secret - why do you choose the x co-ordinate instead of the hash of the secret which is standard practice for stealth addresses <br>
<br>
Sent from my iPhone</div><div><div>
<div><br>
On 24 Apr 2015, at 21:27, Justus Ranvier &lt;<a href="mailto:justus.ranvier@monetas.net" target="_blank">justus.ranvier@monetas.net</a>&gt; wrote:<br>
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<p style="margin:0px">-----BEGIN PGP SIGNED MESSAGE-----</p>
<p style="margin:0px">Hash: SHA1</p>
<p style="margin:0px"><br>
</p>
<p style="margin:0px"><a href="https://github.com/justusranvier/rfc/blob/payment_code/bips/bip-pc01.mediawiki" target="_blank">https://github.com/justusranvier/rfc/blob/payment_code/bips/bip-pc01.mediawiki</a></p>
<p style="margin:0px"><br>
</p>
<p style="margin:0px">This link contains an RFC for a new type of Bitcoin address called a &quot;payment code&quot;</p>
<p style="margin:0px"><br>
</p>
<p style="margin:0px">Payment codes are SPV-friendly alternatives to DarkWallet-style stealth addresses which provide useful features such as positively identifying senders to recipients and automatically providing for transaction refunds.</p>
<p style="margin:0px"><br>
</p>
<p style="margin:0px">Payment codes can be publicly advertised and associated with a real-life identity without causing a loss of financial privacy.</p>
<p style="margin:0px"><br>
</p>
<p style="margin:0px">Compared to stealth addresses, payment codes require less blockchain data storage.</p>
<p style="margin:0px"><br>
</p>
<p style="margin:0px">Payment codes require 65 bytes of OP_RETURN data per sender-recipient pair, while stealth addresses require 40 bytes per transaction.</p>
<p style="margin:0px"><br>
</p>
<p style="margin:0px">-----BEGIN PGP SIGNATURE-----</p>
<p style="margin:0px">Version: GnuPG v1</p>
<p style="margin:0px"><br>
</p>
<p style="margin:0px">iQIcBAEBAgAGBQJVOqCRAAoJECpf2nDq2eYjluEP/RVJk+miDIihY4ilIvUbKvMd</p>
<p style="margin:0px">JLLqHr7Q1dlZyMIG/UqVWdoP5hzg/16B+q2iAB9jXozPnrDp0mggBh6rIGroevAa</p>
<p style="margin:0px">Kqfrs+Rrog1w9auhd67LWORDqav6YIrjTJIxdLxe11IEiq5rWbHPNUEDMzdEmHbz</p>
<p style="margin:0px">QfTH7KWAP2BasO5ETXcfu6BcccrXZ3XOKLON2h3NGD/cEDizY+uT2k3QN54z+KxG</p>
<p style="margin:0px">NB9scKbzVvsJwkyBrgbV+As9H3k6PnFsojYgAaE9gkp7D2+ahjzUiOH5rv6TbbYR</p>
<p style="margin:0px">o2X5MOiTY2/YZEqZPG7IR03ZAgeLVCvXXysjPOfzUKbmTF4w849sm8BuhixzDXHo</p>
<p style="margin:0px">2V/HHKoGclIohcODBCWi0tVQXshZt4QkCNJBW5o3nL6Nn2YOp6hmw8YKAHnw3E7h</p>
<p style="margin:0px">/wIgk5f+NOLl/iIxoAxAdavEj5P6N4ic+OB6MAjnhEilWfBvCIpqWLGNvrtOhEa9</p>
<p style="margin:0px">EnPHcgb4ILBu4OionJhsNpJ/O95C0OEypMm25MIS+rQcV4Uxe5IOS2OuT/GreLET</p>
<p style="margin:0px">n/7Y0mJbqYbLBjVsfS+DNjvsgyJl5AxhcMrdVyXJjSYVcCoRhcoX5Ceidd+YkbHI</p>
<p style="margin:0px">OMs5f63tM1Rgi/WY4Ct80SD5EbULZuu8j1KJ9HPGuMt081JSBH+L5isiKuazPeO+</p>
<p style="margin:0px">SGApMBd4Q89fKzL2djae</p>
<p style="margin:0px">=Dypr</p>
<p style="margin:0px">-----END PGP SIGNATURE-----</p>
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