ContactDiscoveryService VS fog

[1] https://signal.org/blog/private-contact-discovery/

Signal uses SGX for remote attestation, which presumably lets the client verify that the code running on the server is a build of the OSS code and not a modified version. But I don't know the details or if this is reliable.

SGX and remote attestation described here:

https://signal.org/blog/private-contact-discovery/

Signal does private contact discovery and the effort they've gone to to do this is quite impressive.

TEEs have numerous privacy-enhancing applications that may benefit users. One of them is, as discussed earlier, private contact discovery; the Signal application uses a contact discovery service enhanced using Intel SGX, a TEE technology, to protect its users' privacy. A similar application of TEEs is performing malware analysis in a remote cloud service, so that the service may not identify users by the contents of their devices, such as the applications they have installed, especially important as 98.93% of users may be uniquely identified by the list of applications they have installed.

Signal (or, more accurately, one of its predecessors) used to use client-side private set intersection for contact discovery, but this scales poorly [1].

Now they use a solution based on Intel SGX and server-side trusted computing [2].

[1] https://signal.org/blog/contact-discovery/

[2] https://signal.org/blog/private-contact-discovery/

I had an idea that you could shard the blockchain into multiple parallel networks representing a fraction of the total supply each. This could spread tx volume among each sub-network. Combined with something like Fog for txo recovery could greatly increase the upper bound of scaling on the base layer.

https://github.com/mobilecoinfoundation/fog#overview

This explains the issues fairly well. tl;dr most blockchains require a large CPU and/or network expensive sync which is prohibitive on mobile. As a fix/hack many web and mobile apps have a SPOF gateway which the client must trust absolutely.

“Monero isn't fast enough and doesn't support transaction recovery (it also has probabilistic linkage which MobileCoin doesn't due to our use of secure enclaves). We spent almost 18 months building MobileCoin Fog to solve the second problem (https://github.com/mobilecoinfoundation/fog). It's a non-trivial stack of code to allow users to recover strings from servers they don't control without the operators of those servers being able to learn what strings are being recovered. Don't get me wrong, we stand on the shoulders of giants, but there's a lot of new tech here.”

I personally love Dash. One thing that was a requirement for me was that privacy in the system can't be optional if you want to give system-wide guarantees about the privacy of the system. That is to say, non-privacy-protecting transactions weaken the privacy of correlated privacy-protecting transactions. Second, I don't personally think CoinJoin goes far enough, specifically there's still a transaction graph to analyze. MobileCoin does not have a transaction graph which is a distinguishing factor from other cryptocurrencies. Finally, other privacy coins have implemented encrypted ledgers (see CryptoNote), which is something MobileCoin has; to the best of my recollection CoinJoin does actually have an encrypted ledger which is a big distinguishing factor. In order for users to recover transactions from an encrypted ledger, you need an encrypted recovery service which, again to the best of my knowledge, no one had ever invented. This is where Fog comes in, which allows fast mobile recovery of user transactions even in an encrypted ledger (https://github.com/mobilecoinfoundation/fog).

Hi,

Before you label MobileCoin a scam, I would encourage you to take a look at the Github. I think you'll see that we've made a lot of very carefully considered choices on how to deliver a great payments experience without many of the compromises other cryptocurrencies have chosen. Of note, the speed of transactions, much greener energy design, privacy-protections, and mobile-first UX are differentiators. Many cryptocurrencies have some of these features, but I don't know of any other that has all of them.

Believe me, I have a lot of feelings about how absurd cryptocurrency has become in the last decade. At its core, I still believe that there is something beautiful in decentralized ledgers and I think that this is the way that the world will settle debts over the next hundred years. Signal chose MobileCoin because nothing else met their performance and privacy standards. In order to meet those goals we wrote a lot of new technology that is fundamentally different from how other cryptocurrencies are architected today (check out our oblivious RAM implementation, for example: https://github.com/mobilecoinfoundation/fog).

I love Signal and I started MobileCoin to help fund their work. For me, a world with Signal in it is a better place.