Re: [bitcoindev] Re: Knowledge Gathering: SPV Proof Applications In the Wild and Proposed

[Sergio Demian Lerner <sergio.d.lerner@gmail.com>]

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Rootstock uses SPV proofs to power its Bitcoin SPV node that runs in
consensus inside the Bridge smart contract. The bridge uses SPV proofs to
accept peg-ins and peg-outs change, after 100 Bitcoin confirmations.
The system is decentralized: any user can submit Bitcoin headers to build
the Bridge view of Bitcoin. The Bridge maintains the canonical chain and
all potential forks. All forks can be extended with block headers having
the right PoW.
The codebase is based on Bitcoinj.
The system has been running since 2018 without interruptions.
The SPV proof verifier is protected from Merkle node type confusions
(64-byte txs).

Sergio

On Mon, May 25, 2026 at 3:37 PM jeremy <jeremy.l.rubin@gmail.com> wrote:

> I received the below as reply-one and am forwarding with permission:
>
> ------
>
>
> Hi Jeremy,
>
> This is a presentation I did in 2016 on SPV as "Satoshi's scaling
> solution".
>
> There are no new types of proofs, just old fashioned proofs-of-coin and
> proofs-of-spend. My approach was to try to envision what the whole network
> would need to look like.
>
> A common objection to SPV was that full nodes would be "overloaded", so I
> introduced spv-serving light nodes with different services.
>
> A key idea (which is not stated explicitly in the slides) is for a node to
> advertise interest in a set of tx hash stems for which it would provide
> proof services, and for which it wanted to be relayed transactions.  The
> set would contain stems of varying lengths that could be as short as 1 hex
> character or as long as some max.
>
> Wallets would do this same registration to cause transactions to be routed
> to themselves.  Nearly all of those stems would be randomly introduced for
> privacy.
>
> Bloom filters are mentioned as part of a transaction repeater service but
> that was for compatibility with existing SPV wallets of the time.  The main
> idea was to achieve scaling and privacy by the registration scheme.
>
> Hope it's useful in some way!
>
>
> Cheers,
> Tom Harding
>
>
> On Thursday, May 14, 2026 at 10:47:59 AM UTC-4 jeremy wrote:
>
>> Dear Bitcoin Developers,
>>
>> SPV proofs are an important part of Bitcoin's Design, after all Satoshi
>> thought they were worth including in the whitepaper!
>>
>> As far as I'm aware, they have somewhat limited usage in the wild, mainly
>> in Electrum and in Layer 2 Bridges, but it is important that they work
>> correctly.
>>
>> I'd like to gather a bit more detailed information on where and how SPV
>> proofs are currently used, as well as any other proposed uses of SPV proofs.
>>
>> In this Knowledge Gathering, I'd also like to glean a better
>> understanding of what types of commitment structures might work "better"
>> than others for SPV -- e.g., ability to cheaply verify if a block pays a
>> particular address, spends a particular coin, and the exclusion forms (does
>> not pay an address, does not spend a coin) etc, especially in the context
>> of Layer 2 Bridging.
>>
>> Happy International Chihuahua Appreciation Day,
>>
>> Jeremy
>>
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