Decode IdToken using JJWT with RSA

Question

My customer sends to me a JWT, I need to validate this JWT using their public key. I am using Java and JJWT framework to validate this token. I know decode this token using HS256, but using RS256 I don't know.

their configurations is:

Editing here to improve my question. The jjwt example of parse that I am using:

        Claims String secret = "-----BEGIN CERTIFICATE-----myx5ckey-----END CERTIFICATE-----"
    byte[] dataBytes = Base64.getEncoder().encode(secret.getBytes());
    byte[] byteKey = Base64.getDecoder().decode(dataBytes);
    X509EncodedKeySpec X509publicKey = new X509EncodedKeySpec(byteKey);
    KeyFactory kf = KeyFactory.getInstance("RSA");

    PublicKey publicKey = kf.generatePublic(X509publicKey);

    Claims body = null;
    body = Jwts.parser().setSigningKey(publicKey.getEncoded())
            .parseClaimsJws(idToken)
            .getBody();


java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: invalid key format

    at sun.security.rsa.RSAKeyFactory.engineGeneratePublic(RSAKeyFactory.java:205)

How can I validate the received token using the JWKS informations that I show? (imagem above)

Answer 1

I solved my problem.

String secret2 = "myX5c";
        CertificateFactory cf = CertificateFactory.getInstance("X.509");
        Certificate certificate = cf.generateCertificate(new ByteArrayInputStream(DatatypeConverter.parseBase64Binary(secret2)));
        PublicKey publicKey = certificate.getPublicKey();


        Claims body = null;
        body = Jwts.parser().setSigningKey(publicKey)
                .parseClaimsJws(idToken)
                .getBody();

@KcDoD thanks for your tips.