In general I dislike how domains, which should be an unobtrusive out-of-the-way thing that we don't think about much, are taking up so much space in code to express, to the point of them being the single thing preventing `bls_verify` from being expressed in one line of code. Here I reorder arguments and add a default, and make `bls_verify` a one-liner.
Not necessarily convinced that exactly this approach is the way to go, but IMO it's worth considering.
See also #818.
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* Replace custody challenge game with JABS
Replace the existing proof of custody game with a new game ("Justin's Awesome Bit Sum" or JABS) that works as follows:
* The data `D` is split up into 512-byte chunks `D[0] .... D[n-1]`, and use a mix function `mix(subkey, data) -> {0,1}` (currently the first bit of the hash of `subkey+data`). We calculate `M[i] = (mix(D[0]) + ... + mix(D[i-1])) % 2`, and set the custody bit to `M[n-1]`
* Anyone can challenge by providing the full `M` where `M[n-1]` is not equal to the custody bit
* Anyone can respond to a challenge by providing a specific position in `M` along with a branch of the data where `M[i-1] ^ mix(D[i]) != M[i]`
The maximum size of data is now `2**6` epochs * `2**6` blocks * `2**14` bytes = `2**26` bytes, so assuming 512-byte mix chunks the maximum mix size is `2**17` bits or `2**14` bytes. The average mix size is `2**8` bytes.
The 1-round custody game has been implemented. Many bugs squashed, and a bunch of polishing done. Miscellaneous known issues (~8 of them) to be resolved in separate, smaller, PRs.
protolambda
Danny Ryan
Justin
vbuterin
Hsiao-Wei Wang
Alex Stokes