
Ask HN: What are the cons of DAGs as compared to blockchains? - mgalka
Crypto currencies based on directed acyclic graphs (e.g. IOTA) seem to solve nearly all of the biggest problems with blockchains -- scalability, low or 0 transaction costs, no 51% attack, no need for miners.<p>DAGs cannot be used for generalized smart contracts, so they are not a competitor for Ethereum. But do they have any disadvantages as compared to Bitcoin and other pure cryptocurrencies?<p>I assume I&#x27;m missing something, because otherwise DAGs seem too good to be true. And so far there has been little attention paid to them by the crypto ecosystem.
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tromp
The main disadvantage is that their growth rate is uncontrollable. If it's
possible to add billions of tx to the DAG in a day (possibly with some custom
hardware for solving simple PoWs), and a node needs to process those billions
of tx to have absolute confidence that some payment it receives is not double
spent, then the system breaks down.

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dustfinger
Would a tx rate limiter not help here?

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tromp
How do you limit the rate? I only see the requirement of a low-difficulty PoW,
which is easily subverted with some custom hardware.

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throwaway30yo
A problem that the DAGs seem to face is that integration with an exchange is a
much more difficult process. At least with XRB (Which I am most familiar with)
each exchange has to set up multiple hot wallets and ensure they are kept in
sync.

I think XRB is now exchanged on 3-4 sites and they all only have various
levels of support.

I think the DAGs (XRB, Byteball, IOTA and likely many more I am unaware of)
have the potential to be very useful for microtransactions.

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francoisjammin
I am super interested in the answer to this as well. It seems too good to be
true. That is why I have not dipped my toes in RaiBlocks (XRB).

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ezekg
I sent a few test transactions with XRB and they appeared in my wallet within
10 seconds. Confirmed on the network within 1 minute. I read the whitepaper
and it seems solid and seems like it will scale much better than other mined
coins, not to mention it's more energy efficient because of the lack of
mining. Excited to see where it goes, as I'd love to see a coin that is viable
for real-world transactions (honestly, I just dislike carrying/receiving cash
and dealing with banks to use my money). Looking to check out IOTA next.

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quickthrower2
I've been playing with a small amount of IOTA (<$0.01) and found yes txns get
stuck waiting for confirmations for days and it is very hard to force them
through.

Due to the one-use addresses your entire funds are stuck, because you can't
resend from that address, so you can only wait, reattach and 'promote'.
Promote means create a 0-value txn confirming your txn that ends up being more
likely to confirmed itself. Nice in theory.

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vjcucucurg
I own some byteball, rai, and iota. I like the high tps. But im not sure that
no transaction cost is a positive. It makes it easy to spam the network to
bring it down. Having some proof of work to guard against this seems
inefficient and wasteful Why spend time burning electricity when you can just
charge the same amount in transaction charges. A small but real transaction
cost seems cleaner.

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albertgoeswoof
I don’t think any DAGs are running in the real world without a central
conductor for security. Which is a huge attack vector and downside

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dustfinger
I see no reason why one could not develop a DAG based crypto-currency that is
Turing complete to compete with Ethereum.

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mgalka
DAGs do not keep track of the order of transactions, so general purpose smart
contracts are not possible

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arisAlexis
byteball

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flignats
They require mass adoption to work as intended.

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arisAlexis
byteball is a DAG system with smart contracts I suggest people to look into it

