Quote from: St.Bit on January 04, 2014, 07:15:58 AM

Another issue is that YAC needs protection from 51% PoW attacks and with PoS trust=PoW trust we would loose such.

Bitcoin has a unique hash-algorithm so that the bitcoincommunity with their hardware can compute far more efficient than the rest of the world. This makes it extreme hard to attack it with standard computers. Cryptos like LTC are mined with a lot of GPU's which are also not that common.

A CPU on YAC has around the same hash/s as a GPU so a botnet could easily rape us without 51%protection from PoS.
This makes me belive that PoS trust=PoW trust isn't possible without some sort of checkpoints. Somehow I think we need some sort of CentralCheckpointing...

What do you guys think about the following:
A PoS blocks trust is limited to a singe PoWs unless it get's confirmed by CentralAuthority CA in the next block. Such CA only needs to send a txt to the owner of the previous block. This would limit the power of CA to reverse just a few blocks and could only be done once. Everyone that was online would notice such by having 2 different forks which both have a confirmed PoS block in it. Miners are usually always on.

In order to get rid of the Central thing we could allow everyone to send such txts for a fee. Only the authority with the biggest balance get`s accepted and will get a small % reward later on. A minimun for becoming a CA should prevent someone to fake beeing a legit member of our community and a thief would rather steal the whole adress.

If (or better since) this isn't enough damage for someone that abuses his power we could also go where it hurts. I don't see any problem if all miners would agree to never ever accept a txt from an adress that was used to scam the whole community by this. Since freezing funds would also be nessasary to have more than just one guy getting all the rewards this wouldn't go much further. Opening a box we should never even touch... Baaaaad.

EDIT:
Reward could be randomly given to one of the 10 biggest CA-candidates that participated based on howmuch coins they have. Since sending a txt from a wallet has to send the spare change to a new adress we shouldn't go by biggest balance, we should go by biggest output.

A cooldownperiod of [n(no of candidates)+5] PoS-blocks would allow all candidates to participate and reduce the damage a single wallet can do.

No need to add another signing as PoS works in a similar way, anyway. PoS was supposed to be a distributed check-pointing and look where it got us. Wink

Quote from: Balthazar on January 03, 2014, 03:01:46 PM

Quote from: sairon on January 03, 2014, 02:52:56 PM

Would you mind elaborating a bit?

1) You have to maximize an active weight. It doesn't matter how you do so, but you have to do it for any price (even for constant trolling from ignorant kids), because that's necessary to survive.

2) You have to make attack energy expensive, in order to prevent free attack attempts. Otherwise user will be able to use OpenVZ and 10000+ wallet copies to make 10000+ attempts without any problem.

NovaCoin maximizes active weight using a variable RoI and limited block reward. It also implements a variable trust idea, the consequtive PoS or PoW blocks has lower trust in comparison with a hybrid chain. Attacker have to generate a hybrid chain to make success.

1) I assume that by "maximizing active weight" you mean the "number of coins participating in PoS * their coin-age". That's quite difficult to achieve with such little adoption and in this early stage of initial coin distribution. I think we're better off (at least temporarily until YAC economy grows enough) to enforce the rules I proposed. They're easier to implement the right way and have a much lower potential of screwing something up hard.

2) Enforcing a hybrid chain (with alternating PoW/PoS blocks) is IMO a bad idea as the protocol is set to 1-minute PoW and 10-minute PoS target. With my rules hybrid chain is the optimal way when trying to do 51% attack (as you can reduce the "51%" PoW hashing power needed by at most 50% if you have 100% active weight). Still, it would not be expensive enough to attempt, anyway - that's my justification of lowering PoS trust to the level of PoW (I'd lower it even more if only it didn't cause another sort of problems, which it would). It's all about finding the right balance, anyway.

Variable ROI isn't sufficient to prevent a malicious entity wanting to break the network entirely, anyway. As YAC uses a heavily CPU-friendly hashing algorithm, it would be a dumb idea to rely solely on PoW in the era of supercomputers and even the good ol' botnets. So the optimal attack scenario favors stake amount over hashing power to at least try to mitigate the motivation of breaking the netwrok entirely - by forcing the attacker to invest heavily into the coin beforehand, thus inflicting at least some sort of monetary costs to them (botnets are dirt-cheap novadays).

Anyway, I've got the code changes ready. You're all invited to review them. https://github.com/saironiq/yacoin-cc/commit/acf917a2c42cb947b08a9a7878ceafd6045ea24c