Oblivious Message Retrieval - RPGF Nomination

Hello! I am Jay, and I did like to self-nominate myself for the Namada RPGF program to support developing Oblivious message retrieval (OMR) for the Namada ecosystem.

Below I provide a brief description of OMR and its importance for private blockchains (such as Namada). For more information and technical discussions, I would like to direct you to this post.

One side effect of encrypted transactions on private blockchains is users need to download all transactions from the time they were last online and run trial decryption on each of them to identify their pertaining transactions. This does not scale well with blockchain traffic, causing degraded user experience. Due to this, it can become hard for private blockchains to match the user experience of transparent blockchains. Oblivious message retrieval solves this. A server (i.e. a full node) can detect encrypted transactions pertaining to a user and pack only the pertaining ones into a message digest. The user can later retrieve their message digest and decrypt it to find their pertaining transactions. I should note that since the server performs computation on encrypted transactions it never learns which transactions from the set of all transactions were detected pertaining to a given user and are present inside the user’s message digest.

Oblivious message retrieval can become a necessary part of the privacy toolbox of individuals. For Namada, and other private blockchains, it promises good user experience without having to sacrifice privacy. Moreover, OMR is capable of playing a wider role in privacy focussed ecosystems. For example, it enables anonymous asynchronous messaging. That is, you can send data asynchronously between one another without attaching metadata such as receiver/sender’s details. Hence, I believe it is important to support development of Oblivious message retrieval so that it can be adapted in Namada and the wider privacy ecosystem.

Additional links:

  1. Link to my prototype of OMR.
  2. Link to Zcash forum post suggesting ways to preserve privacy of light clients. I think the post does not list OMR because paper introducing OMR was released on a later date. None the less, the post provides a detailed description of caveats associated with alternate options.