Javascript Crypto.sign() 函数使用给定的私钥对消息进行签名

我需要用加密软件在信息上签名.NodeJS中的sign()函数以获取有效的JWT.

Dm2xriMD6riJagld4WCA6zWqtuWh40UzT/ZKO0pZgtHATOt0pGw90jG8BQHCE3EOjiCkFR2/gaW6JWi+3nZp8A==

我试图得到一个签名:

const getJWT = () => {
  const privateKey =
    "Dm2xriMD6riJagld4WCA6zWqtuWh40UzT/ZKO0pZgtHATOt0pGw90jG8BQHCE3EOjiCkFR2/gaW6JWi+3nZp8A==";
  const payload = {
    iss: "test",
    aud: "test.com",
    iat: 1650101178,
    exp: 1650101278,
    sub: "12345678-1234-1234-1234-123456789123"
  };
  const token = encode(payload, privateKey);
  return token
};

const encode = (payload, key) => {
  const header = {
    typ: "JWT",
    alg: "EdDSA"
  };
  const headerBase64URL = base64url(JSON.stringify(header));
  const payloadBase64URL = base64url(JSON.stringify(payload));
  const msg = Buffer.from(`${headerBase64URL}.${payloadBase64URL}`);
  const keyDecoded = Buffer.from(key, "base64");
  const signature = crypto.sign("Ed25519", msg, keyDecoded); //Here is the problem
  const signatureBase64url = base64url(Buffer.from(signature));
  return `${msg}.${signatureBase64url}`;
};

我收到了这个错误:

internal/crypto/sig.js:142
  return _signOneShot(keyData, keyFormat, keyType, keyPassphrase, data,
         ^

Error: error:0909006C:PEM routines:get_name:no start line

  library: 'PEM routines',
  function: 'get_name',
  reason: 'no start line',
  code: 'ERR_OSSL_PEM_NO_START_LINE'

如何将私钥调整为有效格式？