codex-storage-proofs/circuits/storer.circom

pragma circom 2.1.0;

include "../node_modules/circomlib/circuits/poseidon.circom";
include "../node_modules/circomlib/circuits/switcher.circom";
include "../node_modules/circomlib/circuits/bitify.circom";

include "./poseidon-digest.circom";

template parallel MerkleProof(LEVELS) {
    signal input leaf;
    signal input pathElements[LEVELS];
    signal input pathIndices;

    signal output root;

    component switcher[LEVELS];
    component hasher[LEVELS];

    component indexBits = Num2Bits(LEVELS);
    indexBits.in <== pathIndices;

    for (var i = 0; i < LEVELS; i++) {
        switcher[i] = Switcher();

        switcher[i].L <== i == 0 ? leaf : hasher[i - 1].out;
        switcher[i].R <== pathElements[i];
        switcher[i].sel <== indexBits.out[i];

        hasher[i] = Poseidon(2);
        hasher[i].inputs[0] <== switcher[i].outL;
        hasher[i].inputs[1] <== switcher[i].outR;
    }

    root <== hasher[LEVELS - 1].out;
}

template StorageProver(BLOCK_SIZE, QUERY_LEN, LEVELS, DIGEST_CHUNK) {
    // BLOCK_SIZE: size of block in symbols
    // QUERY_LEN: query length, i.e. number if indices to be proven
    // LEVELS: size of Merkle Tree in the manifest
    // DIGEST_CHUNK: number of symbols to hash in one go
    signal input chunks[QUERY_LEN][BLOCK_SIZE]; // chunks to be proven
    signal input siblings[QUERY_LEN][LEVELS];   // siblings hashes of chunks to be proven
    signal input path[QUERY_LEN];               // path of chunks to be proven
    signal input hashes[QUERY_LEN];             // hashes of chunks to be proven
    signal input root;                          // root of the Merkle Tree
    signal input salt;                          // salt (block hash) to prevent preimage attacks

    signal saltSquare <== salt * salt;          // might not be necesary as it's part of the public inputs

    component hashers[QUERY_LEN];
    for (var i = 0; i < QUERY_LEN; i++) {
        hashers[i] = PoseidonDigest(BLOCK_SIZE, DIGEST_CHUNK);
        hashers[i].block <== chunks[i];
        hashers[i].hash === hashes[i];
    }

    component merkelizer[QUERY_LEN];
    for (var i = 0; i < QUERY_LEN; i++) {
        merkelizer[i] = MerkleProof(LEVELS);
        merkelizer[i].leaf <== hashes[i];
        merkelizer[i].pathElements <== siblings[i];
        merkelizer[i].pathIndices <== path[i];

        merkelizer[i].root === root;
    }
}