"So my question to the community is, how invasive is this to bitcoin's
source code?"

I'd say not very considering you have regression testing mode.


On Thu, Apr 17, 2014 at 8:25 AM, Jorge Timón <jtimon@monetize.io> wrote:

> I'm implementing a new testing mode that produces blocks
> periodically. You can get what I have so far here:
>
> https://github.com/jtimon/bitcoin/tree/timed
>
> It depends on pull request #3824 with some improvements on
> CChainParams, but after that the changes required to add this new
> mode are very small:
>
>
> https://github.com/jtimon/bitcoin/commit/445321928a143cb9a6f56777cbb7479dd32c3bcd
>
> I guess I need a new genesis block, different magic numbers, etc. So
> this is definitely not ready.
> You can run it like this:
>
> bitcoind -timedtest -gen=1 blocktime=2000
>
> blocktime defaults to 1000 milliseconds for timedtest mode and 0 for
> the rest of the modes.
>
> What could this testing mode be useful for?
>
> Basically, simulations.
> For example, you could run several nodes implementing different mining
> policies. Let's say I want to mine 50% of the blocks with standard policy,
> 25% with policy A and 25% with policy B. I can run 1 one for each of
> one with block times 2000, 1000 and 1000 respectively.
>
> Maybe I want to detect performance bottlenecks by stressing this mode
> with as many transaction as can be processed, maybe removing the
> block size limits in the simulations.
>
> But this still doesn't serve for hardfork or double-spend attacks
> simulations without calculating any pow, which would be another
> interesting feature for a new testing mode.
> I would like to implement the new mode following as the concept of
> private chains described in freimarkets:
>
> http://freico.in/docs/freimarkets.pdf
>
> https://github.com/jtimon/freimarkets/blob/master/doc/freimarkets_specs.org#private-ledgers
>
> https://github.com/jtimon/freimarkets/blob/master/doc/freimarkets_specs.org#off-chain-transactions
>
> I know this could be considered a "non-bitcoinish" application and
> therefore be controversial as discussed in PR 3824, so I want to keep
> the conversation focused on testing use cases useful to bitcoin itself
> only: additional changes can be implemented elsewhere.
> One way I think you could support chain races simulations by using a
> private mode could be the following:
>
> 1) The private mode works like the timed mode in how often it
>    produces blocks.
>
> 2) In private mode you replace the pow-related fields with a
>    blockPubkeyScript and a lastBlockSigScript fields. In the genesis
>    block, lastBlockSigScript is empty and the initial
>    blockPubkeyScript can be an optional parameter like blocktime. You
>    can set any valid script, probably p2sh, maybe with multisig to
>    allow different nodes to sign.
>
> 3) In this context, longer chains mean "more work". Another way to
>    see it is that all blocks just contain work==1 in them.
>
> So let's say we want to simulate an attack using 50% standard and 50%
> attacker blocks. You set up the private mode script to be a 1 of 2
> multisig and make each node sign always with the same private key
> (maybe an additional parameter).
> You make the attacker reject any blocks from height X that he hasn't
> signed himself to get the result you wanted: the standard node will
> produce blocks on top of the longest chain while the attacker will
> only hash on top of his own blocks.
>
> So my question to the community is, how invasive is this to bitcoin's
> source code?
> In my opinion, done properly could actually result (apart from getting
> the new features) in more readable code, not less, since you will
> probably need to make sure proof of work functionality is properly
> encapsulated during the implementation process (see PR 3839 for a first
> step on that direction).
> But, should I push a private mode to the core or just the timed one
> and implement the private mode elsewhere?
>
> Of course other comments on the parameters, defaults or any other
> design or implementation details are also welcomed.
>
> --
> Jorge Timón
>
> http://freico.in/
>
>
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