Bus Mapping 簡化版實現

Code 範例

這邊先給上 mapping code 範例，第一組為 key-value 的綁定方式

儲存狀態 Storage / Memory ，以這樣表示

def build_mapping():
    keys = [1,3,5]
    values = [2,4,6]

    randomness = hash(keys, values)

    mappings = []

    for key , value in zip(keys,values):
        mappings.append(key + randomness*value)
    return(mappings)

想證明某個 key-value 在 key-value 中，可以通過 3 個 plookup 實現

1. 證明 mapping 的 key 在 keys 表中
2. 證明 mapping 的 value 在 values 表中
3. 證明 mapping 的 mappings 中

def open_mapping(mappings, keys, values):
    randomness = hash(keys,values)
    index = 1
    # Prover can chose any mapping, key , value
    mapping = plookup(mappings)
    key = plookup(keys)
    value = plookup(values)
    # But it has to satisfy this check
    require(mappings[index] == key[index] + randomness*value[index])
    # with overwhelming probablitiy will not find an invalid mapping.

這邊可以看出完整的 bus_mapping 結構，下一章節會做個簡單的版本

bus_mapping[global_counter] = {
    type_flag = ["stack", "memory", "storage"],
    rw_flag,
    key,
    value,
    index: opcode,
    call_id: call_id,
    prog_counter: prog_counter
}

實作 class

拿上一章看的完整 bus-mapping 實現，這邊我用一個簡單的 class 去實現，之後串接 EVM Proof 和 State Proof 後續會做大更動，所以目前先做簡單的設計

class BusMapping:
    def __init__(self):
        self.bus_mapping = {
					stack: [],
					memory: [],
					storage: [],
					pc: 0,
				}

    @staticmethod
    def build_mapping(keys, values):
				randomness = hash((tuple(keys), tuple(values)))
        
        mappings = []
        for key, value in zip(keys, values):
            mappings.append(key + randomness * value)
        return mappings
    
    @staticmethod
    def open_mapping(mappings, keys, values):
        randomness = hash((tuple(keys), tuple(values)))
        index = 1
        mapping = ZKEVM.plookup(mappings)
        key = ZKEVM.plookup(keys)
        value = ZKEVM.plookup(values)
        assert mappings[index] == key[index] + randomness * value[index], "Mapping validation failed!"

    @staticmethod
    def plookup(list_to_search):
        return list_to_search[0]