BIP352: Add extra encoding formats for scanning and spending #2026

1. 
   junderw commented at 5:25 am on November 1, 2025: contributor

   Based on a discussion I started on Delving Bitcoin

   Also related: BTC Transcripts

   BIP authors: @josibake @RubenSomsen

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   These two new encodings are a way for Silent Payment users to:

   1. Delegate scanning and wallet UTXO management to self hosted services like BTCPayServer
   2. Encode secret information including birthday and labels used, so that silent payment wallets can be exported and imported across wallets without information loss.

   I was debating whether to make the non-address encodings into descriptors instead. But that would be an easy change to make.

   Just creating this PR so that specific discussions about wording can take place.

   Thanks.

2. BIP352: Add extra encodings 51e1a91af1
3. jonatack added the label Proposed BIP modification on Nov 1, 2025
4. jonatack added the label Pending acceptance on Nov 1, 2025
5. 
   jonatack commented at 10:32 pm on November 1, 2025: member

   cc BIP authors @josibake and @RubenSomsen for feedback
6. BIP352: Make max_label to encode used labels ae9cd401df
7. in bip-0352.mediawiki:255 in 51e1a91af1

   250+
   251+* Let ''b<sub>scan</sub> = Receiver's scan private key''
   252+* Let ''b<sub>spend</sub> = Receiver's spend private key''
   253+* Let ''birthday = The block height at wallet creation''
   254+** If ''birthday'' is unknown or if recovering from a BIP39 seed, use block height 842579 (May 8, 2024)<ref name="why_birthday_842579"></ref>
   255+* Let ''labels = [m<sub>1</sub>, m<sub>2</sub>, ..., m<sub>n</sub>]'' an optional array of label integers
   

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   nymius commented at 3:36 pm on November 3, 2025:

   I prefer a single number to show the stop limit instead of a list of labels, to push users towards a “dense” range of labels and produce a shorter, fixed size encoding, i.e., spspend<scan><spend><birthday>15 for a wallet with at most 15 revealed labels. The change label is always assumed. The possible value will range between [1, 2**32 - 1].

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   jvgelder commented at 4:32 pm on November 3, 2025:

   I think this is also the intention of the BIP authors as they mention Let Bm = Bspend + hash(bscan || m)·G where m is an incrementable integer starting from 1

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   junderw commented at 10:17 am on November 4, 2025:

   Good idea. Done.

Contributors
junderw jonatack nymius jvgelder

Labels
Proposed BIP modification Pending acceptance