Bitcoin Optech newsletter #399 is here:

• describes how wallet fingerprinting can damage payjoin privacy
• summarizes a proposal for a wallet backup metadata format
• links to post-quantum research using Isogenies
• points to the recently assigned BIPs for GSR
• examines SHRIMPS post-quantum signatures
• Optech Newsletter #399 Podcast
  https://bitcoinops.org/en/newsletters/2026/04/03/

Armin Sabouri posted to Delving Bitcoin about how differences in payjoin implementations make it possible to fingerprint payjoin transactions and can damage payjoin’s privacy...
https://bitcoinops.org/en/newsletters/2026/04/03/#wallet-fingerprinting-risks-for-payjoin-privacy

Pythcoiner posted to the Bitcoin-Dev mailing list about a new proposal for a common structure for wallet backup metadata...
https://bitcoinops.org/en/newsletters/2026/04/03/#draft-bip-for-a-wallet-backup-metadata-format

Conduition wrote on Delving Bitcoin about his research into the suitability of Isogeny-Based Cryptography (IBC) as a post-quantum cryptosystem for Bitcoin...
https://bitcoinops.org/en/newsletters/2026/04/03/#compact-isogeny-pqc-can-replace-hd-wallets-key-tweaking-silent-payments

Rusty Russell wrote on the Bitcoin-Dev mailing list that the first two BIPs of the Great Script Restoration (or Grand Script Renaissance) have been submitted for BIP numbering...
https://bitcoinops.org/en/newsletters/2026/04/03/#varops-budget-and-tapscript-leaf-0xc2-aka-script-restoration-are-bips-440-and-441

Jonas Nick writes on Delving Bitcoin about a new semi-stateful hash-based signature construction for post-quantum Bitcoin...
https://bitcoinops.org/en/newsletters/2026/04/03/#shrimps-2-5-kb-post-quantum-signatures-across-multiple-stateful-devices

Bitcoin Optech will host an audio recap discussion of this newsletter streaming live on X/Twitter Tuesday at 16:30 UTC.