Subject: Re: [bitcoin-dev] BIP Number Request: Addresses over Audio

From: Jorge Timón <[email-masked]>
Date: Fri, 12 Aug 2016 17:49:23 +0200

No, anyone with the bip32 public seed can do the same as the receiver as
"watch only". The only difference is rhat the receiver can actually spend
the coins. As gmaxwell explained, if it's expensive for everyone, it will
be also expensive for the receiver (assuming no interaction after the bip32
public seed is transfered).

Something different would be to give a different bip32 public seed to each
payer.  That way they can simply start with zero an increment with each new
payment. With those assumptions, the receiver could start listening to new
addresses only after they receive something in the previous address.

Probably not useful for this case, just thinking out loud about using bip32
public seeds instead of one use addresses when there's going to be several
payments from the same payer to the payee.

On Aug 12, 2016 2:37 PM, "Erik Aronesty via bitcoin-dev" <
[email-masked]> wrote:
>
> I'm imagining a "publishable seed" such that:
>
>  - someone can derive a random bitcoin address from it -  and send funds
to it.
>  - the possible derived address space is large enough that generating all
possible addresses would be a barrier
>  - the receiver, however, knowing the private key, can easily scan the
blockchain fairly efficiently and determine which addresses he has the keys
to
>  - another interested party cannot easily do so
>
> Perhaps homomorphic encryption may need to be involved?
>
>
> On Thu, Aug 11, 2016 at 8:36 PM, Gregory Maxwell <[email-masked]> wrote:
>>
>> On Thu, Aug 11, 2016 at 8:37 PM, Erik Aronesty via bitcoin-dev
>> <[email-masked]> wrote:
>> > Still not sure how you can take a BIP32 public seed and figure out if
an
>> > address was derived from it though.   I mean, wouldn't I have to
compute all
>> > 2^31 possible public child addresses?
>>
>> Which would take a quad core laptop about 8 hours with competent software
>>
>> And presumably you're not using the whole 2^31 space else the receiver
>> also has to do that computation...
>
>
>
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