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Simple JWT example for k6 load testing tool
import crypto from "k6/crypto";
import encoding from "k6/encoding";
const algToHash = {
HS256: "sha256",
HS384: "sha384",
HS512: "sha512"
function sign(data, hashAlg, secret) {
let hasher = crypto.createHMAC(hashAlg, secret);
// Some manual base64 rawurl encoding as `Hasher.digest(encodingType)`
// doesn't support that encoding type yet.
return hasher.digest("base64").replace(/\//g, "_").replace(/\+/g, "-").replace(/=/g, "");
function encode(payload, secret, algorithm) {
algorithm = algorithm || "HS256";
let header = encoding.b64encode(JSON.stringify({ typ: "JWT", alg: algorithm }), "rawurl");
payload = encoding.b64encode(JSON.stringify(payload), "rawurl");
let sig = sign(header + "." + payload, algToHash[algorithm], secret);
return [header, payload, sig].join(".");
function decode(token, secret, algorithm) {
let parts = token.split('.');
let header = JSON.parse(encoding.b64decode(parts[0], "rawurl"));
let payload = JSON.parse(encoding.b64decode(parts[1], "rawurl"));
algorithm = algorithm || algToHash[header.alg];
if (sign(parts[0] + "." + parts[1], algorithm, secret) != parts[2]) {
throw Error("JWT signature verification failed");
return payload;
export default function() {
let message = { key2: "value2" };
let token = encode(message, "secret");
console.log("encoded", token);
let payload = decode(token, "secret");
console.log("decoded", JSON.stringify(payload));
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