Oblivious Message Retrieval

Hello Zcash community!
We recently posted a ZOMG application to develop Oblivious Message Retrieval (OMR), a technique to support private transaction retrieval for light clients.

Here is the link to the proposal: ZF Grants - Oblivious Message Retrieval
Here is the full version of the proposal: Research Proposal for Oblivious Message Retrieval - HackMD
Please see section 11 in our paper for a detailed discussion regarding Zcash integration considerations.

We would love to hear your feedback or comments and would be happy to answer any questions of yours!
Thank you all!


Welcome to the Zcash community Thomas!

I am glad to see a research driven grant that is in line with my post:

Thank you for submitting this proposal to research and deliver an alternative way to improve the operations & privacy of light client communication.


Welcome to the Zcash community Thomas!

This is an awesome proposal that can improve privacy and the UX of Zcash wallets.

Is OMR similar to Fuzzy Message Detection (FMD)? In other words, does the compact encrypted digest sent by lightwalletd servers contain only the associated notes of each recipients or will there be false positives too like in FMD?

Anyway, good luck with the project!

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Thank you for your support for your post @aiyadt!

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Thank you for your support @tokidoki!

OMR is different from FMD. OMR always provides full privacy, and the privacy is independent of the false positive rate.
In general, the digest would contain false positives, but with only a very small probability (e.g., in the paper/demo, we set false positive rate to be 2^{-21}, and can be set to smaller like 2^{-40} without affecting privacy).
There are several other differences and we provide a more comprehensive comparison with FMD in table 1+ section 2.1 in our paper.


Got it. So, OMR is not decoy-based privacy which is great!

Can’t wait to see this in action. :grin:

Not sure when ZOMG will decide on the proposal but it’s a hard yes from me.

P.S: I’m not on ZOMG board.


Thank you for your support! The importance of your support is definitely independent of the ZOMG-board-ness :wink:.

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I approve this grant as a community member.


Thank you for your support @dontbeevil!

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Congratulations ZCash Community. Something is going right if these are the grant applications we are receiving.

Good luck @thomaslzy!


Thank you for your support @GGuy! Glad that you like our project and proposal. Happy holidays :smiley:

Hi @thomaslzy, I’m glad to inform you that the ZOMG is supportive of your grant application! Your work will contribute towards the goal of buttressing end-to-end privacy coverage across Zcash’s different clients/user journeys. @tromer of course is a welcome source of confidence and oversight.

Two things:

  1. Could you integrate OMR with Zecwallet Lite @adityapk00 and Zwallet @hanh, in addition to Nighthawk? These are important wallets to the Zcash community (Zecwallet having the longest history and a large userbase)
  2. It seems that your PhD admission details are not yet finalized. We’d like to express that the grant is covered/capped up to $98k. If the amount increases for any reason, you will have to resubmit to the next ZOMG panel (which starts some time in January)

Hello @ml_sudo,
That’s great news! Thank you for your and ZOMG’s support.

To answer your questions:

  1. We are surely happy to also work with Zecwallet Lite @adityapk00 and Zwallet @hanh team to integrate the OMR library with these two wallets. Please also note that as indicated in the application, the full integration of the OMR library with any wallet is not part of this project, but rather we will support integrations done by the wallets’ primary developers (including trying to adapt our library to their needs).
  2. I surely understand that. Thank you for the reminder.

Thanks again for your and the community’s support!


Congratulation on the grant Thomas! In the Zcash community, you get what you put in!
Myself and @NighthawkWallet developers are excited to work with you to deliver the end-to-end support for private transaction retrieval for light clients. :raised_hands:


Thank you @aiyadt! Exited to work with you and @NighthawkWallet team on private transaction retrieval as well :-).


Thank you, ZOMG and everyone else who weighed in above, for your support of this project!

I’m really excited about this project for many reasons, including:

  • It addresses a longstanding gap in building scalable privacy-preserving payments systems.
  • Following zk-SNARKs and Halo ZKP accumulators, this puts the Zcash ecosystem at the forefront of yet another type of “moon math” cryptography: Homomorphic Encryption.
  • This is a super fertile opportunity for real-world problems to drive scientific innovation. Working with Thomas on OMR, we kept asking: What would Zcash integration look like? What would be its bottlenecks and possible attacks? And this got translated into stronger security notions and improved techniques (some already reflected in the first paper, some forthcoming).
  • Time is right. The FHE cryptographic toolset has just now reached the level of maturity where we can pull this kind of thing with decent performance. And simultaneously, blockchain scalability is on everyone’s mind. Mix in Zcash’s privacy ethos, and we have the perfect recipe for impact.
  • @thomaslzy is the perfect person for this job. He’s been astoundingly productive and inventive in solving the OMR problem from the moment he heard about it, and is deeply familiar with the state of the art in FHE.
  • I love seeing ZOMG expanding its grants scope and flexing its muscles.

I’ve been keeping low because I didn’t want to personally weigh in on that last point… Great to see the proposal spoke for itself! Yes, I will continue working with Thomas on this project (as a research colleague and academic supervisor), and in particular, will strive to convey Zcash-specific tech/community/deployment considerations and opportunities.