Implement and integrate new Incremental Merkle Tree
This supersedes #823.
----
This is an implementation of a new incremental merkle tree with
* no memory safety issues
* a more sensible internal design
* better space efficiency (tree representation, witnessing)
* simpler API
It is intended that this tracks the behavior of the previous tree, which it does, as verified by tests. I even wrote a little circuit for testing that all the paths work.
This PR also integrates the tree into the codebase and deprecates the old tree in almost all of our code. (I left it alone in `zerocashTest` but everything else has been changed.)
This change is compatible with the testnet but you will need to clear your *local* blockchain data out since the serialized representation of the merkle tree is now different.
Closes#517, Closes#519, Closes#591, Closes#460, Closes#473
This is a new implementation of the incremental merkle tree used by our
scheme to witness commitments to spendable value. It serves as a fixed-sized
accumulator.
This new construction has a much simpler API surface area, avoids memory
safety issues, remains pruned at all times, avoids serialization edge cases,
has more efficient insertion, and is abstract over the depth and hash
function used at the type level.
Further, it lays the groundwork for efficient "fast-forwarding" of witnesses
into the tree as the treestate is updated.
After a new block is found or after a few nonces have been tried (currently
after every nonce), the miner checks for global changes. If any of these are
triggered, a new block is built from scratch, which re-initialises the Equihash
input. But if none of the checks are triggered, the miner just updates nTime and
continues mining - without updating the Equihash input to account for the new
block header. This bugfix corrects the behaviour by regenerating the Equihash
input in both situations.
Automated performance measurement
Supersedes #843 because that one would have merged into the wrong branch. (Oh yeah and I rebased).
**REBASED AND FORCE PUSHED**
Implement Founders' Reward
More info: https://z.cash/blog/funding.html
The consensus rule is as follows:
```
All blocks before the first subsidy halving block, with the exception of
the genesis block, must contain an output which sends 20% of the block
subsidy value to a scriptPubKey `FOUNDERS_REWARD_SCRIPT`.
```
Right now, `FOUNDERS_REWARD_SCRIPT` is a 2-of-3 multisig P2SH.
Closes#125
All blocks before the first subsidy halving block, with the exception of
the genesis block, must contain an output which sends 20% of the block
subsidy value to a scriptPubKey `FOUNDERS_REWARD_SCRIPT`.
