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Merge pull request #201 from remicolin/main
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add SplitBytesToWords circuit to bytes.circom
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Divide-By-0 authored Jun 26, 2024
2 parents 919ab82 + 6e1b374 commit 29d5c87
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33 changes: 33 additions & 0 deletions packages/circuits/tests/splitBytesToWords.test.ts
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import { wasm as wasm_tester } from "circom_tester";
import path from "path";
import { bigIntToChunkedBytes, Uint8ArrayToCharArray } from "@zk-email/helpers/src/binary-format";


describe("SplitBytesToWords Helper unit test", () => {
jest.setTimeout(0.1 * 60 * 1000);
let circuit: any;

beforeAll(async () => {
circuit = await wasm_tester(
path.join(__dirname, "./test-circuits/splitBytesToWords-test.circom"),
{
recompile: true,
include: path.join(__dirname, "../../../node_modules"),
// output: path.join(__dirname, "./compiled-test-circuits"),
}
);

});

it("should split correctly according to bigIntToChunkedBytes function", async function () {
const bytes = new Uint8Array(256).map(() => Math.floor(Math.random() * 256));
const bytesBigInt = bytes.reduce((acc, val) => (acc << 8n) | BigInt(val), 0n);
const ts_split_to_words = bigIntToChunkedBytes(bytesBigInt, 121, 17);
const ts_split_to_words_bigint = ts_split_to_words.map((word) => BigInt(word));
const witness = await circuit.calculateWitness({
in: Uint8ArrayToCharArray(bytes)
});
await circuit.assertOut(witness, { out: ts_split_to_words_bigint });
});

});
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pragma circom 2.1.6;

include "../../utils/bytes.circom";

component main = SplitBytesToWords(256,121,17);

36 changes: 36 additions & 0 deletions packages/circuits/utils/bytes.circom
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Expand Up @@ -111,3 +111,39 @@ template DigitBytesToInt(n) {

out <== sums[n];
}


// NOTE: this circuit is unaudited and should not be used in production
/// @title SplitBytesToWords
/// @notice split an array of bytes into an array of words
/// @notice useful for casting a message or modulus before RSA verification
/// @param l: number of bytes in the input array
/// @param n: number of bits in a word
/// @param k: number of words
/// @input in: array of bytes
/// @output out: array of words
template SplitBytesToWords (l,n,k) {
signal input in[l];
signal output out[k];

component num2bits[l];
for (var i = 0 ; i < l ; i++){
num2bits[i] = Num2Bits(8);
num2bits[i].in <== in[i];
}
component bits2num[k];
for (var i = 0 ; i < k ; i++){
bits2num[i] = Bits2Num(n);
for(var j = 0 ; j < n ; j++){
if(i*n + j >= 8 * l){
bits2num[i].in[j] <== 0;
}
else{
bits2num[i].in[j] <== num2bits[l - (( i * n + j) \ 8) - 1].out[ ((i * n + j) % 8)];
}
}
}
for( var i = 0 ; i< k ; i++){
out[i] <== bits2num[i].out;
}
}

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