[Lightning-dev] Backward deterministic R Value

[Mats Jerratsch]

What about if Alice does not want to disclose R? Bob could have taken
too much fee and Alice does not agree to accept a payment too small.

While there is technically not really a security problem in disclosing
the R values when the payment isn't in the current commitment, the whole
idea of 'proof-of-payment'/'pay-to-contract' relies on only revealing R
for an accepted payment.

Otherwise, knowing R is no longer proof of having made a payment.

Am 08/03/2016 um 07:19 schrieb CJP:
> I was wondering: how does deriving R values from a tree structure work
> for larger Lightning networks? I guess it could work between two nodes,
> if they keep track of the same tree, but if different transactions
> follow different routes, does that mean the tree structure somehow has
> to be shared across all nodes? The alternative is that intermediate
> nodes still have to remember old R values.
> 
> CJP
> 
> 
> Nicolas Dorier schreef op di 08-03-2016 om 13:53 [+0900]:
>> Great, indeed we had same idea, I don't see how it solve the hashes in
>> advance. 
>> As Alice knows
>> H(1000000) = <random secret seed>).
>> If she need the hash to the first commitment she need to hash the random secret
>> seed 1000000 times. I think it is exactly the same problem as it is the exact
>> same idea said differently.
>>
>> On Tue, Mar 8, 2016 at 8:31 AM, Rusty Russell <rusty at rustcorp.com.au>
>> wrote:
>>         Nicolas Dorier <nicolas.dorier at gmail.com> writes:
>>         > One way deterministic RValue Generation
>>         
>>         Hi Nicolas,
>>         
>>                 Yes, in fact shachain is a variant of this which
>>         avoids
>>         generating several million hashes in advance.  Interesting, I
>>         suggested
>>         using hashing in the Deployable Lightning paper but didn't
>>         actually
>>         spell out the idea.  Hmm....
>>         
>>         Seems like it orignated from Adam Back:
>>         
>>         https://lists.blockstream.io/pipermail/lightning-dev/2015-May/000000.html
>>         
>>         Cheers,
>>         Rusty.
>>
>>
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> 
> 
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-- 
Mats Jerratsch
Backend Engineer, Blockchain
e: mats at blockchain.com
PGP: https://pgp.mit.edu/pks/lookup?op=get&search=0x7F3EC6CA

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