locally_redactable_nizk.zok

import "./commitment" as Commitment
import "hashes/sha256/512bitPacked" as sha256packed

/*
*   c0 - First part of the hash c_k_i (collision key)
*   c1 - Second part of the collision key
*   keyIndex - The i-th key (probably unused)
*   blockNumber - The redactable-blockchain block number
*   commitment - the c0 commitment (collision key)
*   G, H - public parameter of the commitment scheme
*   
*   message - committed message (c0)
*   randomness - randomness of the committed message
*/


def main(field c0, field c1, field keyIndex, field blockNumber, field commitment, field G, field H, private field message, private field randomness) -> (bool):

    //Check that the committed message is the same (assertion)
    new_commitment = Commitment(G, H, message, randomness)
    
    bool result = if new_commitment == commitment then true else false fi
    
    //Initialize the array to zero
    field[2] init_value = [0, 0]
    field[4][2] h = [init_value; 4]
    


    field[2] first_chain_element = sha256packed([0, 0, blockNumber, message])

    
    h[0] = first_chain_element
    
    for field i in 1..3 do
        field h0 = h[i-1][0]
        field h1 = h[i-1][1]
        
        
        tmp = sha256packed([0, blockNumber, h0, h1])
        
        h[i] = tmp
        
    endfor
    
    return if result && h[keyIndex][0] == c0 &&  h[keyIndex][1] == c1 then true else false fi
    //return h