Hacker News Reader

Comment by Quanttek | Hacker News Reader

Can anyone please tl;dr what's so special about Grin and how it achieves that?

It may scale really, really well "The state a given node in a MimbleWimble blockchain needs to maintain is very small (on the order of a few gigabytes for a bitcoin-sized blockchain, and potentially optimizable to a few hundreds of megabytes)."

https://github.com/mimblewimble/grin/blob/master/doc/intro.m...

Also, anonymous transactions.

Downside: you cannot "send coins to an address" as in bitcoin, you must have interaction with the other party to create a transaction.

Doesn't this just mean adoption is easily farmed out to various communication protocols that do it better? (Signal, Whatsapp, Telegram, Threema). Basically handing them a ready-made drop-in cryptocurrency system ?

Any regular centralized system doesn't need any of this, they can do just fine with mature, stable, very well understood and crazy fast RDBM systems.

Hurts anonymity if you have to do peer to peer transfers of the file, plus you have issues around resending/etc. (payments are somewhat different from other messages). Even with IM-based exchange, I'd probably use something else and then pass a message instead.

The wallet already supports interacting through keybase.

It's worth expanding on that downside: the interaction can be asynchronous, it's not a requirement that the two parties be online at the "same time" or even in the same week.

In other words, less of a downside than it may seem, but it is a real shortcoming since it precludes sending to the equivalent of a cold wallet.

How would an asynchronous transaction work? If you're posting your side of the transaction publicly, doesn't that expose you to a MITM or spoofing attack?

No, the handshake requires the two public keys engaging in the transaction, no one else can complete it.

They can be MITMed by an attacker spoofing the identity, but this is no different from a MITM inserting a different BTC address into a communication stream.

How does that work in practice?

Do payments take place over a tcp connection? How do you find your payment peer?

The wallet exposes an interface that allows different 'plugins' to be implemented. Right now you can exchange slates (the transaction data) via http, file or keybase. It is possible to build plugins that use any communication channel (Telegram, Signal, email etc)

Anonymous transactions, small block chain (scales with number of unspent outputs, not transactions), achieved by commutative and associative properties of addition over Elliptical Curve Cryptography.

Grin gives strong anonymity guarantees but maintains most of the other public verification properties of a traditional blockchain like Bitcoin. It also includes some cool scalability optimizations to the Bitcoin-style of blockchain.

Anonymity is maintained with a cool trick called a blinding factor, where a secret value is drummed up for each transaction and used to obfuscate the data that is publicly displayed on the blockchain. Combining that with range proofs allows all involved parties to verify that the transaction was completed for the specified amount, and that no money was created out of thin air.

Scalability is boosted with transaction cut-through - a neat trick that lets unnecessary “intermediate” transactions get eliminated when a miner assembles a block. This means that nodes on the network can store the entire chain state really efficiently because all you need to know are the total coins in circulation, the UTXO set, and the kernels for each transaction.

I can’t do the whole thing justice in this tl;dr, so read the technical explanation here for more info if it piques your interest:

https://github.com/mimblewimble/grin/blob/master/doc/intro.m...

Grin hides the transaction amount and provides some transaction relationship obfuscation depending on how powerful your adversary is. I think Grin is cool and I'm very supportive of it, but much more work needs to be done to understand the anonymity provided especially against active attacks.

Reply on news.ycombinator.com