Quote from: rat4 on April 01, 2014, 06:35:16 AM

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Quote from: artiface on April 01, 2014, 01:59:56 AM

That is YOUR reply I quoted.

You must have read the answer at one point, because YOU commented that your question was answered, but I will summarize it again here just to be perfectly clear.

Blackcoin use POS 0.3.0 protocol which has no known vulnerabilities at this time
The "attack" suggested is impossible because coins do not stake on age alone, therefore making deposits at small intervals in no way guarantees you will generate POS blocks at those intervals. In fact splitting coins to generate these intervals will make the chance of staking at each interval even less

Right, it uses "POS 0.3.0 protocol which has no known vulnerabilities at this time" in the context of a PoS/PoW hybrid, right? It has never been tested in the context of pure PoS, right?

I will restate: If i said said anything further about it on the blackcoin thread, I would have been ran out of there and labeled as a FUDer.
Similar to how what I am saying now, not on the blackcoin thread, is drawing so much heat.

I'm not giving you heat, i'm only answering your question.. again.

Saying Sunny King's fix only applies to POS/POW hybrids is incorrect, it fixed the POS protocol. Period.

The timebomb attack is not feasible because coins do not stake on age alone, there are other factors. Even if you could guarantee that all your coins ages were spaced at a minimum interval there is no guarantee they will all stake at their intervals. Also POS blocks have a target time interval, so coins that were eligible to stake too soon would not generate blocks any faster than the target interval, there is no way that one person could force their coins to be the ones to generate stake for many consecutive intervals. This attack is pure nonsense.

But Sunny King fixed PoS in the context of PoS/PoW hybrid, not pure PoS. Right?

Since there have not been any other pure POS coins yes the fix was originally applied to a POS/POW hybrid. Nevertheless the fix is for the POS protocol and did nothing to POW. The fix ensured that POS was a secure way to generate blocks to secure a blockchain. If you know of any vulnerabilities in POS please make them known so they can be addressed.

I don't know the specific vulnerabilities, I'm not saying that there necessarily are any. My argument is purely from a logic standpoint. If the security of PoS was in any way dependent upon PoW in the PoS/PoW hybrid system, then just because the PoS security flaws were fixed in that context doesn't mean they will be fixed when PoS is standing alone, or that new security flaws wouldn't be introduced when PoS stands alone. So the question is, did Sunny build/fix PoS to be completely secure standing alone or was it in anyway dependent on PoW? I guess this is ultimately what I am trying to figure out.

Sunny built them to be dependent on each other. POW is a proven system. POW/POS is a proven system. POS is not and may be vulnerable to attack.

OP's point is that a POW/POS system with very small rewards creates a weak POW system that someone could exploit and it would essentially be the same as a standalone POS system which may be vulnerable.

You clearly did not understand the OP. That is not the OP's point at all. The OP's point is that POW/POS hybrid is vulnerable to a double spend attack by a POS block negating/orphaing a POW chain with enough blocks to have confirmed transactions.

I expect you have never looked at the source code of a POW/POW hybrid, because it it very clear POS and POW are not dependent on each other in any way. They are completely separate methods. It is true that POS only has never been tried before, but the POS system is secure in itself and has no known vulnerabilities. POW is a proven system with a known vulnerability called 51% attack which is why POS was added. POS/POW may be vulnerable by the method explained in the OP. POS alone, again has no known vulnerabilities besides a 51% attack which would require owning 51% of the coins which would mean you already basically control the money supply and would devalue your own coins.

looking at your posts and the OP
"double spend attack requires 1 PoS block and low hashing power."

So wouldn't this method of attack require that you control/know precisely when you are going to receive a PoS block, so that you can orphan your transactions that you confirmed on the PoW chain you control (otherwise somebody else will have a greater chance of getting the next PoS block, unless you control 51%)?
You made it sound earlier like it is not possible to control when a PoS block will be generated:
"The "attack" suggested is impossible because coins do not stake on age alone, therefore making deposits at small intervals in no way guarantees you will generate POS blocks at those intervals. In fact splitting coins to generate these intervals will make the chance of staking at each interval even less"
So, are there ways to control/know the timing of PoS block generation even though coinage is not the sole determining factor?
If so, wouldn't that mean pure PoS is vulnerable too?

Attacker should wait for 1 PoS block and delay announcing this block.

So, in that case, what is preventing an attacker from waiting for multiple PoS blocks and delaying announcing the multiple PoS blocks to form a string of PoS blocks similar to a TX attack chain like the one anonymousg64 was talking about? If it is not possible to wait/delay more than one block per wallet, then one could easy use multiple wallets.

Nothing prevents. Chance to find even 2 blocks in a row is low.
Long chain of PoS blocks is realistically only for exchanges with old coins in cold wallet.

But like you said "Attacker should wait for 1 PoS block and delay announcing this block." Why couldn't this process be simply reiterated to form a string? You wouldn't need to "find" >2 blocks in a row, you would just need to announce them in a row. Or am I missing something?

My edit of what I said above, must have been editing while you responded:
"So, in that case, what is preventing an attacker from waiting for multiple PoS blocks and delaying announcing the multiple PoS blocks to form a string of PoS blocks similar to a TX attack chain like the one anonymousg64 was talking about? If it is not possible to wait/delay more than one block per wallet, then one could easy use multiple wallets. If the timing of generating/announcing a single PoS block can be controlled, what is preventing reiteration of the process to control a series of single blocks?
Also, what would prevent another block from being announced at that same time or right before you? Say you control when you can announce your PoS block, but does that mean you can control when other people generate/announce theirs?"

Similar to mercSuey's point that PoS is a stochastic process,

What would prevent another block from being announced at that same time or right before you? Assuming you can control when you can announce your PoS block, does that mean you can control when other people generate/announce theirs?