No, I am talking about the chance of being the user who gets the next stake-block.
In some of your copies of the blockchain+wallet some other user will get the next stake block, if you only stake for example 1/10th of your coin age on a block (because of wanting to get 10 blocks in a row, for example).
On all the copies where it is not you who gets the next block, well those copies never happened. Your "real" attack chain you pick to build next block on will be one of the copies in which it was you who got the next block.
So for example suppose you have ten times enough coin age to get a 1 in 1000 chance of winning the stake block.
You can thus afford to try for ten blocks in a row, with 1 in 1000 chance each block.
Now make 1000 copies of the chain, so a thousand of "you" are, in secret, trying for the next block with 1/1000 chance each.
What is your chance then?
Now suppose you make 10,000 clones of "you" all in parallel.
Etc.
The fact it does not cost "work", just a bunch of disk space and a little bit of computation, per copy you run in parallel, is why Cunicula wanted "work" to be somehow involved in using your "stake". Not separate blocks even, just make it cost to use stake. In at least one of his suggestions for example, the weight would be some function of work and stake, chosen so it would take a lot of work to beat a little stake but pure stake with no work could be beaten by less stake with some work.
-MarkM-
You always have factor of others wanted broke your operation.
1/1000 x1000 = 100% chance wont never exist in real world because there always will be others with some coin age or exchange ext and those factors will cut your chance to 50% maybe less per block but always to have 100% chance you need shut them down others from network.
It is no so easy even with such "bot" net like that you need to be majority.
https://en.bitcoin.it/wiki/Proof_of_Stake"Double-spending prevention
A good level of security can be achieved by waiting for a block to be cemented. By that time it is safe to assume that the network recognizes this block and will not easily switch to a different block, even if a longer branch is presented.
A more authoritative confirmation is enabled by waiting for a signature block. Once a block achieves a majority (and some more time is allowed for this majority to spread in the network), it is extremely unlikely that the network will ever switch away from this block."
______________________________________________________________________
So when you trying get coin age up while being off line and not stacking:
Coin-age_t = Coin-age_t-1 + 1
You are losing weight weight - is something that can allow you have higher chance to mine POS block.
New weight = 0.9 * Old weight + 0.1 * Balance
If a signature is not provided by the address in a signature block, its weight decreases:
New weight = 0.9 * Old weight
Coins with stake with big coin age aren’t majority of coins which will be used to confirming operation they can refuse fake blockchain
you still need majority of coins to confirm double spend.
