Replace custody challenge game with JABS #812
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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.
JustinDrake
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Mar 20, 2019
Text moved away from `1_shard-data-chains.md` (see #812 rewrite).
This was referenced Mar 20, 2019
hwwhww
reviewed
Mar 21, 2019
specs/core/1_shard-data-chains.md
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| assert state.validator_registry[reveal.validator_index].slashed_epoch > get_current_epoch(state) | ||
| slash_validator(state, reveal.validator_index, reveal.revealer_index) | ||
| state.validator_balances[reveal.revealer_index] += base_reward(state, index) // MINOR_REWARD_QUOTIENT | ||
| elif reveal.period == state.validator_registry[reveal.validator_index].next_subkey_to_reveal and reveal.mask == ZERO_HASH: |
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By the variable names, it seems "Subkey reveals" section only processes early_subkey_reveals; are they all in is_early_reveal cases? Or it's better to adjust the variable naming?
JustinDrake
approved these changes
Mar 28, 2019
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Replace the existing proof of custody game with a new game ("Justin's Awesome Bit Sum" or JABS) that works as follows:
Dis split up into 512-byte chunksD[0] .... D[n-1], and use a mix functionmix(subkey, data) -> {0,1}(currently the first bit of the hash ofsubkey+data). We calculateM[i] = (mix(D[0]) + ... + mix(D[i-1])) % 2, and set the custody bit toM[n-1]MwhereM[n-1]is not equal to the custody bitMalong with a branch of the data whereM[i-1] ^ mix(D[i]) != M[i]The maximum size of data is now
2**6epochs *2**6blocks *2**14bytes =2**26bytes, so assuming 512-byte mix chunks the maximum mix size is2**17bits or2**14bytes. The average mix size is2**8bytes.