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From: Tamas Blummer <tamas@bitsofproof.com>
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Date: Fri, 28 Mar 2014 14:18:10 +0100
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To: Mike Hearn <mike@plan99.net>
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] BIP 70 refund field
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May I ask how the current payment protocol is supposed to handle =
salaries? I hope you do not assume the employee creates a payment =
request, since he does not
even calculate the amount. There you go where a channel I described is =
definitelly needed.

Tamas Blummer
http://bitsofproof.com

On 28.03.2014, at 12:30, Tamas Blummer <tamas@bitsofproof.com> wrote:

> Instead of a payment request and refund, businesses would actually =
need a payment channel, that once established allows for multiple =
payments back and forth between counterparties.
>=20
> One might have a number of open channels until the business =
relationship is assumed. The customer might decide to close the channel =
explicitelly once he does no longer expect a payment.=20
>=20
> Regards,
>=20
> Tam=E1s Blummer
> http://bitsofproof.com
>=20
> On 28.03.2014, at 12:07, Mike Hearn <mike@plan99.net> wrote:
>=20
>> Modern devices like smartphones and tablets do not have swap files. =
This design is chosen to ensure responsive, fluid UI that can avoid =
blocking on disk regardless of how much multi-tasking is done, but it =
creates ripples that impact everything else.
>>=20
>> One implication of this is that on these devices, we cannot store all =
keys or transactions in memory forever. BIP 70 has an expiry field for =
PaymentRequests that we can use to allow us to eventually stop loading =
those keys into RAM - at that point payments to those keys would no =
longer be recognised. But there's no equivalent for refund addresses.
>>=20
>> More generally, though we re-used the output structure to define the =
refund, we didn't (for some reason that I forgot) reuse PaymentDetails, =
even though the payment details for a refund are indeed PaymentDetails.
>>=20
>> Though I am loathe to go back and redesign this part of BIP 70 so =
soon after we shipped v1, it seems to me like the refund feature may be =
hard to implement on phones if there's no time limit for when you can =
receive a refund. Otherwise a wallet has to be looking out for refunds =
for payments you may have made years ago. So perhaps we should add a new =
refund field that embeds a PaymentDetails structure instead of being =
just a list of outputs.
>>=20
>> We could try and solve this problem some other way purely internally, =
by doing a kind of wallet-specific swapping process in which things like =
Bloom filters are calculated without all keys in them being held in =
memory at once (perhaps caching filters for old parts of the key chain =
on disk), so you can have "infinite" wallets, but eventually the huge =
Bloom filters that would result would hurt efficiency in other ways. So =
key expiry seems pretty fundamental to scalability.
>>=20
>>=20
>> =
--------------------------------------------------------------------------=
----
>> _______________________________________________
>> Bitcoin-development mailing list
>> Bitcoin-development@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>=20


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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Diso-8859-1"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">May I =
ask how the current payment protocol is supposed to handle salaries? I =
hope you do not assume the employee creates a payment request, since he =
does not<div>even calculate the amount. There you go where a channel I =
described is definitelly needed.<div apple-content-edited=3D"true"><br =
style=3D"color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; =
font-style: normal; font-variant: normal; font-weight: normal; =
letter-spacing: normal; line-height: normal; orphans: 2; text-align: =
-webkit-auto; text-indent: 0px; text-transform: none; white-space: =
normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; =
-webkit-text-stroke-width: 0px; "><span style=3D"color: rgb(0, 0, 0); =
font-family: Helvetica; font-size: medium; font-style: normal; =
font-variant: normal; font-weight: normal; letter-spacing: normal; =
line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: =
0px; text-transform: none; white-space: normal; widows: 2; word-spacing: =
0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; =
display: inline !important; float: none; ">Tamas Blummer</span><br =
style=3D"color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; =
font-style: normal; font-variant: normal; font-weight: normal; =
letter-spacing: normal; line-height: normal; orphans: 2; text-align: =
-webkit-auto; text-indent: 0px; text-transform: none; white-space: =
normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; =
-webkit-text-stroke-width: 0px; "><span style=3D"color: rgb(0, 0, 0); =
font-family: Helvetica; font-size: medium; font-style: normal; =
font-variant: normal; font-weight: normal; letter-spacing: normal; =
line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: =
0px; text-transform: none; white-space: normal; widows: 2; word-spacing: =
0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; =
display: inline !important; float: none; "><a =
href=3D"http://bitsofproof.com">http://bitsofproof.com</a></span>
</div>
<br><div><div>On 28.03.2014, at 12:30, Tamas Blummer &lt;<a =
href=3D"mailto:tamas@bitsofproof.com">tamas@bitsofproof.com</a>&gt; =
wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite"><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Diso-8859-1"><div style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div =
apple-content-edited=3D"true">Instead of a payment request and refund, =
businesses would actually need a payment channel, that once established =
allows for multiple payments back and forth between =
counterparties.</div><div apple-content-edited=3D"true"><br></div><div =
apple-content-edited=3D"true">One might have a number of open channels =
until the business relationship is assumed. The customer might decide to =
close the channel explicitelly once he does no longer expect&nbsp;a =
payment.&nbsp;</div><div apple-content-edited=3D"true"><br></div><div =
apple-content-edited=3D"true"><span style=3D"font-family: Helvetica; =
font-size: medium; font-style: normal; font-variant: normal; =
font-weight: normal; letter-spacing: normal; line-height: normal; =
orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: =
none; white-space: normal; widows: 2; word-spacing: 0px; =
-webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; display: =
inline !important; float: none; ">Regards,</span><br style=3D"font-family:=
 Helvetica; font-size: medium; font-style: normal; font-variant: normal; =
font-weight: normal; letter-spacing: normal; line-height: normal; =
orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: =
none; white-space: normal; widows: 2; word-spacing: 0px; =
-webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><br =
style=3D"font-family: Helvetica; font-size: medium; font-style: normal; =
font-variant: normal; font-weight: normal; letter-spacing: normal; =
line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: =
0px; text-transform: none; white-space: normal; widows: 2; word-spacing: =
0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; =
"><span style=3D"font-family: Helvetica; font-size: medium; font-style: =
normal; font-variant: normal; font-weight: normal; letter-spacing: =
normal; line-height: normal; orphans: 2; text-align: -webkit-auto; =
text-indent: 0px; text-transform: none; white-space: normal; widows: 2; =
word-spacing: 0px; -webkit-text-size-adjust: auto; =
-webkit-text-stroke-width: 0px; display: inline !important; float: none; =
">Tam=E1s Blummer</span><br style=3D"font-family: Helvetica; font-size: =
medium; font-style: normal; font-variant: normal; font-weight: normal; =
letter-spacing: normal; line-height: normal; orphans: 2; text-align: =
-webkit-auto; text-indent: 0px; text-transform: none; white-space: =
normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; =
-webkit-text-stroke-width: 0px; "><span style=3D"font-family: Helvetica; =
font-size: medium; font-style: normal; font-variant: normal; =
font-weight: normal; letter-spacing: normal; line-height: normal; =
orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: =
none; white-space: normal; widows: 2; word-spacing: 0px; =
-webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; display: =
inline !important; float: none; "><a =
href=3D"http://bitsofproof.com/">http://bitsofproof.com</a></span>
</div>
<br><div><div>On 28.03.2014, at 12:07, Mike Hearn &lt;<a =
href=3D"mailto:mike@plan99.net">mike@plan99.net</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><div =
dir=3D"ltr">Modern devices like smartphones and tablets do not have swap =
files. This design is chosen to ensure responsive, fluid UI that can =
avoid blocking on disk regardless of how much multi-tasking is done, but =
it creates ripples that impact everything else.<div>
<br></div><div>One implication of this is that on these devices, we =
cannot store all keys or transactions in memory forever. BIP 70 has an =
expiry field for PaymentRequests that we can use to allow us to =
eventually stop loading those keys into RAM - at that point payments to =
those keys would no longer be recognised. But there's no equivalent for =
refund addresses.</div>
<div><br></div><div>More generally, though we re-used the output =
structure to define the refund, we didn't (for some reason that I =
forgot) reuse PaymentDetails, even though the payment details for a =
refund are indeed PaymentDetails.</div>
<div><br></div><div>Though I am loathe to go back and redesign this part =
of BIP 70 so soon after we shipped v1, it seems to me like the refund =
feature may be hard to implement on phones if there's no time limit for =
when you can receive a refund. Otherwise a wallet has to be looking out =
for refunds for payments you may have made years ago. So perhaps we =
should add a new refund field that embeds a PaymentDetails structure =
instead of being just a list of outputs.</div>
<div><br></div><div>We could try and solve this problem some other way =
purely internally, by doing a kind of wallet-specific swapping process =
in which things like Bloom filters are calculated without all keys in =
them being held in memory at once (perhaps caching filters for old parts =
of the key chain on disk), so you can have "infinite" wallets, but =
eventually the huge Bloom filters that would result would hurt =
efficiency in other ways. So key expiry seems pretty fundamental to =
scalability.</div>
<div><br></div><div><br></div></div>
=
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ment mailing list<br><a =
href=3D"mailto:Bitcoin-development@lists.sourceforge.net">Bitcoin-developm=
ent@lists.sourceforge.net</a><br><a =
href=3D"https://lists.sourceforge.net/lists/listinfo/bitcoin-development">=
https://lists.sourceforge.net/lists/listinfo/bitcoin-development</a><br></=
blockquote></div><br></div></blockquote></div><br></div></body></html>=

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