[quote=“No_2, post:7, topic:3043”]1.

When you say ‘difficulty’ what do you mean? Can you point me at where ‘difficulty’ is defined in the code? Is it network difficulty? If so would that mean if the hashing power applied to PPC goes up it becomes harder to successfully mine PoW blocks as PoS blocks have a higher weighting so are more readily accepted by the network?[/quote]

Minting and mining each have their own difficulty.

When more coins are used to mint, the POS difficulty increases.

When more hashing power is used to mine, the POW difficulty increases.

And of course, the higher the difficulty, the harder it is to find a block.

In the source code, the difficulty of a block is calculated from the nBits variable of this block (GetBlockDifficulty function in main.h).

[quote=“No_2, post:7, topic:3043”]2.

From what I understood PoW is supposed to atrophy gracefully in PPC, but will never reach zero PoW. Is this correct or will PoW blocks one day no longer be valid on the network?[/quote]

The reward of a POW block decreases when the POW difficulty increases.

As the hashrate is supposed to increase with time (because of more efficient mining hardware), on average the POW reward is supposed to decline continuously, but that doesn’t change the validity of POW blocks.

The community could decide at some point to modify the protocol and disable POW blocks, but that’s not the case for the moment.

[quote=“No_2, post:7, topic:3043”]3.

As PPC matures will block generation time remain roughly constant, I understand blocks are spaced at about every 10 minutes, but as the system matures what enforces that blocks are generated every 10 minutes on average by PoS? Or have I misunderstood something.[/quote]

The POS difficulty adapts continuously so that the average time between two POS blocks is 10 minutes.

[quote=“No_2, post:7, topic:3043”]4.

The likelihood of mining a block is how many coins you have over 30 days old. (From what I can tell this is true and it’s not calculated as say number of coins * number of days). If so why was this implementation decision taken? It means people can split their coins into multiple wallets to get a better spread of successfully mining PoS blocks. Unless I’ve misunderstood something here.[/quote]

In fact the probability of minting a POS block depends on number_of_coins * day_weight, where: day_weight = min(days - 30, 60).

You can check the CheckStakeKernelHash function in kernel.cpp, it contains a few comments explaining the formula used for minting.

You can also see the probability of finding a POS block with the calculator at http://poscalculator.peercointalk.org.

[quote=“No_2, post:7, topic:3043”]5.

If a part of the blockchain has not been checkpointed and it contains one PoW block and then a chain of PoS blocks what’s to stop someone who holds a sizeable amount of coins (in different transactions) creating a new branch replacing the PoW block and orphaning that branch with their coin age? If this is possible does it have any detrimental effect?[/quote]

This attacker would also have to replace all the POS blocks after the POW blocks for his chain to try to become the main chain. It would require a huge amount of mature coins.

You can check the topic at http://www.peercointalk.org/index.php?topic=3141.0 which contains calculations on the probability of blockchain reorganization.

[quote=“No_2, post:7, topic:3043”]6.

Do you know of any existing tools with which to look at the current block chain and check the ratios of PoW to PoS blocks going back over time?[/quote]

There’s http://peerchain.net where you can see the ratio on the last 2016 blocks, as well as charts of inflation, rewards, number of POS or POW blocks, supply, difficulties, etc…