Knowledge Gathering: SPV Proof Applications In the Wild and Proposed
5 messages, 14 May to 4 Sep 2026. Started by Jeremy Rubin.
Jeremy Rubin, Ekrem BAL, Olaoluwa Osuntokun, Sergio Demian Lerner, conduition
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
Hi Jeremy,
For Citrea/Clementine, we currently use SPV-style proofs in two main places.
First, on the Citrea side, the Bridge system contract uses Bitcoin transaction inclusion proofs to accept peg-ins/deposits. See:
The contract checks inclusion through Citrea's Bitcoin light client contract. More details here:
<https://docs.citrea.xyz/developer-documentation/system-contracts/bitcoin-light-client>
Second, in the Clementine Bridge proof, we use SPV proofs for verifying operator payout transactions. If an operator is challenged, the operator proves that there exists a payout transaction paying the withdrawal. See:
On your question about commitment structures, I think being able to verify that a particular coin was not spent in a block might be helpful, as it could make creating SNARK proofs for operator honesty easier in some bridge designs.
Best, Ekrem BAL On Thursday, May 14, 2026 at 10:47:59 AM UTC-4 jeremy wrote:
Quoted text (23 lines)
> 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 >
Taproot Assets uses SPV proofs in the proof file format for an asset. Each asset starts at a gensis point, then proves that the rules of the overlay layer were followed each each new state transition. Each state transition includes an SPV proof of the transaction that commits to the state transition.
An upcoming revamp of the LN gossip protocol also has a cut out to optionally include an SPV proof with a channel announcement message. This makes the protocol more light client friendly, as otherwise a light client would need to fetch tens of thousands of blocks to verify that a channel actually exists.
It isn't specified today, but a future extension to the `channel_update` message could include a merkle proof of a _spent_ funding output to provide a verifiable gossip layer proof that a channel has been closed. Today setting a disabled bit in the channel update is used in place, but that's overloaded with other signals (eg: the peer is offline).
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> does not spend a coin
If the Merkle Tree were actually a Sparse Merkle Tree, then we'd have a succinct way proving that a given transaction wasn't in a block. If such a commitment were added over the set of spent outputs, then you could also succinctly prove that a transaction wasn't spent in a block.
Such an STXO commitment would also be useful for SwiftSync as then peers are able to verify the integrity of the undo data.
-- Laolu
On Thu, May 14, 2026 at 7:47 AM jeremy <jeremy.l.rubin@gmail•com> wrote:
Quoted text (33 lines)
> 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 > > -- > You received this message because you are subscribed to the Google Groups > "Bitcoin Development Mailing List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to bitcoindev+unsubscribe@googlegroups•com. > To view this discussion visit > https://groups.google.com/d/msgid/bitcoindev/a3049fd5-e001-4d3a-9c99-d5629f47dfd8n%40googlegroups.com > <https://groups.google.com/d/msgid/bitcoindev/a3049fd5-e001-4d3a-9c99-d5629f47dfd8n%40googlegroups.com?utm_medium=email&utm_source=footer> > . >
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:
Quoted text (73 lines)
> 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 >> > -- > You received this message because you are subscribed to the Google Groups > "Bitcoin Development Mailing List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to bitcoindev+unsubscribe@googlegroups•com. > To view this discussion visit > https://groups.google.com/d/msgid/bitcoindev/9001a42f-b497-41c1-895d-3ec902f2413cn%40googlegroups.com > <https://groups.google.com/d/msgid/bitcoindev/9001a42f-b497-41c1-895d-3ec902f2413cn%40googlegroups.com?utm_medium=email&utm_source=footer> > . >
Hey Jeremy,
Just wanted to include DropKick here. DropKick is a PQ rescue protocol that uses SPV-like proofs of block inclusion to prove that an honest user knew a secret before a quantum attacker did, i.e. a commit/reveal protocol.
Details here: https://conduition.io/bitcoin/dropkick/ and here: https://groups.google.com/g/bitcoindev/c/6SqWPfBf-p0
regards, conduition On Thursday, June 4th, 2026 at 10:26 PM, Sergio Demian Lerner <sergio.d.lerner@gmail•com> wrote:
Quoted text (60 lines)
> 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 > > > > -- > > You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. > > To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups•com. > > To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/9001a42f-b497-41c1-895d-3ec902f2413cn%40googlegroups.com. > > -- > You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. > To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups•com. > To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/CAKzdR-pSKPXjBnWJZMASDRZve5Y1ekeTo7eG_f%3DWV-vVn1xZPQ%40mail.gmail.com.