# Request for Proposals: Note Discovery Protocol

**URL:** <https://forum.aztec.network/t/request-for-proposals-note-discovery-protocol/2584>\
**Category:** Aztec\
**Tags:** rfp\
**Created:** [November 29, 2023, 2:57pm UTC](https://forum.aztec.network/t/request-for-proposals-note-discovery-protocol/2584 "2023-11-29T14:57:47Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![Anon](https://avatars.discourse-cdn.com/v4/letter/a/47e85d/32.png) [@Anon](https://forum.aztec.network/u/Anon)\
**Post date:** [January 18, 2024, 8:47am UTC](https://forum.aztec.network/t/request-for-proposals-note-discovery-protocol/2584/3 "2024-01-18T08:47:25Z")

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> [@\[Proposal\] View Tag Batch PIR](https://forum.aztec.network/t/proposal-view-tag-batch-pir/3193):
>
> A [note discovery](https://forum.aztec.network/t/request-for-proposals-note-discovery-protocol/2584) protocol. Notes expose a 16-bit view-tag H(shared\_secret || offset)[:2] ([[1]](https://github.com/ScopeLift/umbra-protocol/issues/377#issuecomment-1212627024), [[2]](https://eips.ethereum.org/EIPS/eip-5564), [[3]](https://github.com/monero-project/research-lab/issues/73)), over which [batch PIR](https://eprint.iacr.org/2022/1262.pdf) [[4]](https://github.com/mhmughees/vectorized_batchpir) queries are made, reducing sync bandwidth of notes by up to 98%. Details tx = { ephemeral\_pk, notes: [{view\_tag, ciphertext}, ..] } view\_tag = H(dh\_shared\_secret || offset)[:2] offset increments for repeated shared\_secrets. e.g. if a tx sends 3 notes to 2 addresses, the view-tags would be H(secret\_1 || 0), H(secret\_1 || 1), H(secret\_2 || 0). To ensure no pri…

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