nested json JWT nimbus-jose -jwt library

Question

I'm trying to create a nested json JWT following the example provided over here http://connect2id.com/products/nimbus-jose-jwt/examples/signed-and-encrypted-jwt

import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;

import com.nimbusds.jose.*;
import com.nimbusds.jose.crypto.*;
import com.nimbusds.jwt.*;


    // Generate 256-bit AES key for HMAC as well as encryption
    KeyGenerator keyGen = KeyGenerator.getInstance("AES");
    keyGen.init(256);
    SecretKey secretKey = keyGen.generateKey();

    // Create HMAC signer
    JWSSigner signer = new MACSigner(secretKey.getEncoded());

    // Prepare JWT with claims set
    JWTClaimsSet claimsSet = new JWTClaimsSet();
    claimsSet.setSubject("alice");
    claimsSet.setIssueTime(new Date());
    claimsSet.setIssuer("https://c2id.com");

    SignedJWT signedJWT = new SignedJWT(new JWSHeader(JWSAlgorithm.HS256), claimsSet);

    // Apply the HMAC
    signedJWT.sign(signer);

    // Create JWE object with signed JWT as payload
    JWEObject jweObject = new JWEObject(
        new JWEHeader.Builder(JWEAlgorithm.DIR, EncryptionMethod.A256GCM)
            .contentType("JWT") // required to signal nested JWT
            .build(),
        new Payload(signedJWT));

    // Perform encryption
    jweObject.encrypt(new DirectEncrypter(secretKey.getEncoded()));

    // Serialise to JWE compact form
    String jweString = jweObject.serialize();

The problem I'm having the resultant jweString is not coming correctly

eyJhbGc.
.6Ne
.tw8z

I'm getting 4 parts instead of 3 parts and there is one empty part

 eyJhbGc.
           .6Ne

Answer 1

The general format of a JWE has five parts, <Header>.<EncryptedKey>.<InitializationVector>.<Ciphertext>.<AuthenticationTag>. In some cases, like using direct encryption that is in the example, there is no encrypted key and that part is left empty. So you should be getting a JWE with five parts where one part is empty that looks something like, eyJjdHkiOiJKV1QiLCJlbmMiOiJBMjU2R0NNIiwiYWxnIjoiZGlyIn0..PVEd_V4E8qyppt6u.UOLp2qTNMw3iA9tyTEDHeJAdTczzI5uP4BkXHQSC6U73kywATBbvdWqz9nilsSWr1y-E1duTMvRL7hzDyyWPMZnpfnCWsjhzZtTnd22HODMWUpU.CoQq987RvHGIN5D6HhrjiQ