Hello IOTA Forum

Beginner questions about tangle

https://forum.helloiota.com/Topic998.aspx

By seongmin - 15 Nov 2017

Hello Smile

I had some unanswered questions about tangle. I posted the questions on reddit, but did not get a single reply.

Some things I were curious about:

1. A new transaction is added to the tangle after proof of work. Does that proof of work depend on the hash of previous two tips the new transaction is validating, just like in traditional blockchains? What is the exact POW each device has to perform?

2. How are parasite chains prevented? Why does the attacker need omnipresence if he can launch a subtangle containing a fraudulent transaction with more tips, against an honest competing transaction?

3. So if I understand correctly, a transaction is confirmed if all(or over whatever threshold a merchant sets, like 95%) tips directly or indirectly point to that node. How will a merchant or a IoT node come to derive the percentage without having access to all tip information? (What if there are too much tips that selecting 100 sample tips with MCMC won't result in a single reference to the transaction you want to confirm).

4. I read the tangle currently does not prune invalid, forgotten tips. If they keep sticking around and eventually increase in count, would it not be possible to get a high(90%~100%) reference rate in future transactions? Or are they marked as invalid by the system and not counted in the tip reference percentage?

Thank you so much!