feat: preferable to have chacha take in bytes instead of bits.

[0xJepsen]

          I think it would be preferable to have this take in bytes instead of bits. But maybe its not a big deal at all.

Originally posted by @Autoparallel in #51 (comment)

Like mentioned it might not be a big deal. I think when we generate witvalues for this i would be happy to be involved. If it seems difficult then we can work on this.

[0xJepsen]

Added a helper for this here

web-prover-circuits/circuits/utils/array.circom

Lines 516 to 549 in cabfa34

	// // from little endian to 32 bit words
	// // example:
	// 0, 1, 0, 1, 0, 0, 0, 0, => 80
	// 0, 1, 0, 1, 0, 1, 0, 0, => 84
	// 0, 1, 0, 1, 0, 1, 0, 0, => 84
	// 0, 1, 0, 0, 1, 0, 0, 0, => 72
	// shoud be encoded as
	// 72, 84, 84, 80
	template fromLittleEndianToWords32() {
	signal input data[32];
	signal output words[4];
	component Bits2Num[4];
	for(var i = 3; i >= 0; i--) {
	Bits2Num[i] = Bits2Num(8);
	for(var j = 7; j >= 0; j--) {
	Bits2Num[i].in[7-j] <== data[i*8 + j];
	}
	words[3-i] <== Bits2Num[i].out;
	}
	}
	template fromWords32ToLittleEndian() {
	signal input words[4];
	signal output data[32];
	component Num2Bits[4];
	for(var i = 3; i >= 0; i--) {
	Num2Bits[i] = Num2Bits(8);
	Num2Bits[i].in <== words[3-i];
	for(var j = 7; j >= 0; j--) {
	data[i*8 + j] <== Num2Bits[i].out[7-j];
	}
	}
	}

and tests here

web-prover-circuits/circuits/test/utils/array.test.ts

Lines 467 to 503 in cabfa34

	describe("fromLittleEndianToWords32", () => {
	let circuit: WitnessTester<["data"], ["words"]>;
	it("fromLittleEndianToWords32", async () => {
	circuit = await circomkit.WitnessTester(`fromLittleEndianToWords32`, {
	file: "utils/array",
	template: "fromLittleEndianToWords32",
	});
	console.log("#constraints:", await circuit.getConstraintCount());
	let input = [
	0, 1, 0, 1, 0, 0, 0, 0, 0,
	1, 0, 1, 0, 1, 0, 0, 0, 1,
	0, 1, 0, 1, 0, 0, 0, 1, 0,
	0, 1, 0, 0, 0
	];
	await circuit.expectPass({data: input}, {words: [72, 84, 84, 80]})
	});
	});
	describe("fromWords32ToLittleEndian", () => {
	let circuit: WitnessTester<["words"], ["data"]>;
	it("fromWords32ToLittleEndian", async () => {
	circuit = await circomkit.WitnessTester(`fromWords32ToLittleEndian`, {
	file: "utils/array",
	template: "fromWords32ToLittleEndian",
	});
	console.log("#constraints:", await circuit.getConstraintCount());
	let input = [72, 84, 84, 80];
	await circuit.expectPass({words: input}, {data: [
	0, 1, 0, 1, 0, 0, 0, 0, 0,
	1, 0, 1, 0, 1, 0, 0, 0, 1,
	0, 1, 0, 1, 0, 0, 0, 1, 0,
	0, 1, 0, 0, 0
	]})
	});
	});

However i was experiencing an problem when making the switch. Probably not too much more work on top of this. The main complexity is that the 32 bit words are little endian encoded mean the byte order is reversed before changing to bits.