JWT EdDSA (Ed25519)

EdDSA (Edwards-curve Digital Signature Algorithm) using Ed25519 is the most modern JWT signing algorithm. It produces 64-byte signatures (same as ES256) and signs deterministically: no random nonce: which eliminates the entire class of ECDSA nonce-reuse attacks (including the 2010 PS3 private-key extraction). It is also the fastest JWT signing algorithm. Defined in RFC 8037.

Key facts and signature size

Property	EdDSA
Type	Asymmetric (Edwards-curve, Ed25519)
Key	256-bit Ed25519 key
Signature size	64 bytes (same as ES256)
Security	~128-bit; deterministic signing (no nonce)
Compatibility	Growing: jose, PyJWT ≥2.x, jjwt, go-jose; not jsonwebtoken

When to use

Use EdDSA for greenfield systems where your full library stack supports it: deterministic signing closes the ECDSA nonce risk, signatures are 64 bytes, and signing/verification are the fastest of any JWT algorithm. EdDSA is the strongest choice when you control the issuer and every verifier and can confirm support across the whole path.

When not to use

EdDSA support is not universal: jsonwebtoken (the most popular Node.js library) does not support it: use jose instead. Older deployments, FIPS-restricted environments, and some cloud-provider token-validation toolchains may not support EdDSA. If you integrate with third-party systems or identity providers that default to RS256, EdDSA may not be accepted. Always verify support across every library in your verification path before adopting it.

Code examples

Generate an Ed25519 key pair

          # OpenSSL 1.1.1+
openssl genpkey -algorithm ed25519 -out ed25519-private.pem
openssl pkey -pubout -in ed25519-private.pem -out ed25519-public.pem

// Node.js
const { generateKeyPairSync } = require("crypto");
const { privateKey, publicKey } = generateKeyPairSync("ed25519", {
  publicKeyEncoding: { type: "spki", format: "pem" },
  privateKeyEncoding: { type: "pkcs8", format: "pem" },
});
        

Sign and verify (Node.js: jose, not jsonwebtoken)

          import { SignJWT, jwtVerify, importPKCS8, importSPKI } from "jose";

const privateKey = await importPKCS8(edPrivateKeyPem, "EdDSA");
const publicKey = await importSPKI(edPublicKeyPem, "EdDSA");

const token = await new SignJWT({ sub: "user_123" })
  .setProtectedHeader({ alg: "EdDSA", kid: "ed25519-key-v1" })
  .setExpirationTime("15m")
  .setIssuer("https://auth.example.com")
  .setAudience("https://api.example.com")
  .sign(privateKey);

const { payload } = await jwtVerify(token, publicKey, {
  issuer: "https://auth.example.com",
  audience: "https://api.example.com",
});