51% attack resistance?

[elambert]

Which coins are resistant to 51% attacks? Why aren't they all?

[sor.rge]

There are no public implementations resistant to 51% attacks.

[elambert]

Solid coin?

[Balthazar]

SolidCoin is vulnerable to double-spend by owner of enough coins amount (1M or more).

[elambert]

SolidCoin is vulnerable to double-spend by owner of enough coins amount (1M or more).

So no working solution to 51% attack at this time? Other than overpowering a potential attacker? Seems with the abundance of coins coming into play, mining will become so diversified that coins will be attacked and killed (like pwc). I guess this is the digital version of natural selection. The weak will die off and only the strong will survive. Pretty cool. Be careful where u invest ur money!

[bitdwarf]

A 51%-type PoS attack is very self destructive though, the attacker is damaging themself by decreasing the coin's value.

OP asked for "resistant" not "immune", so all PoW+PoS coins would deserve some consideration.

[Balthazar]

A 51%-type PoS attack is very self destructive though, the attacker is damaging themself by decreasing the coin's value.

OP asked for "resistant" not "immune", so all PoW+PoS coins would deserve some consideration.

Don't forget that you don't need 51% of stake weight to perform successful double-spend. 20-25% of total stake weight (not coins) will be enough for successful attack against current PoS+PoW implementations without checkpointing.

Stake weight maximization + PoW blocks rate increasing + balanced PoS/PoW weighting will resolve this problem. NovaCoin developed this way in 0.4.1 => 0.4.2 => 0.4.3.

[bitdwarf]

That's why I said 51%-type. It still takes some balls to attack a coin you have a 25% stake in.

[Balthazar]

That's why I said 51%-type. It still takes some balls to attack a coin you have a 25% stake in.

25% stake weight, not 25% stake or 25% of stakes volume. It's not the same...

Just an example, if average stakes age is 1/3 of maximum, you can use outputs with maximum age to reduce required coins amount dramatically.

[coinerd]

I see the phrase "51% attack" used all the time it's like "the bogeyman".

if you mean a double-spend then no coin can resist it in theory if you have the majority of the hashing power on a blockchain you can write almost what you want to it.

51% isn't necessarily going to be enough, in a POW scenario.  I don't understand the POS math so I can't speak on required percentages or weights for those, it seems some of them may require (much) less than 51% of the network stake to pull a double-spend like attack.

There was a thread about powercoin being "51% attacked" I didn't have time to research it but just scanning it sounded like a blockchain switch of some sort. I suspect that one would take more than 51% too but not sure.

Are there other "51% attacks"?