function hexStringToU8Array(hexString) {
if (hexString.length % 2 !== 0) {
throw new Error("Invalid hex string length");
}
const u8Array = new Uint8Array(hexString.length / 2);
for (let i = 0; i < hexString.length; i += 2) {
u8Array[i / 2] = parseInt(hexString.slice(i, i + 2), 16);
}
return u8Array;
}