sun.security.mscapi.RSAPrivateKey cannot be cast to java.security.interfaces.RSAPrivateKey

I am trying to use Jose (https://bitbucket.org/b_c/jose4j/wiki/Home) to generate a signed JsonWebToken. I am running into a problem creating the RsaKeyPairs that I need to use in the signature of the token.

This is the code I am using to generate the public/private Keys and I need to turn this to String so I can store them in the database and then retrieve them.

WebKeyManager wkm = null;
Object obj;
EncryptionKey encKey = null;
RsaJsonWebKey rsaJsonWebKey = null;

try
{
     wkm = new WebKeyManager();
     int    keySize = 512;

     // Initialize KeyPairGenerator.

     SecureRandom random = SecureRandom.getInstanceStrong(); //cryptographically strong random number generator

    // Generate an RSA key pair, which will be used for signing and verification of the JWT, wrapped in a JWK               
    rsaJsonWebKey = RsaJwkGenerator.generateJwk(keySize, random.getProvider().getName(),random);

   // Give the JWK a Key ID (kid), which is just the polite thing to do
    rsaJsonWebKey.setKeyId(""+System.currentTimeMillis());

   String json = rsaJsonWebKey.toJson(OutputControlLevel.INCLUDE_PRIVATE);

} catch (Exception e) { e.printStackTrace(); }

The Problem I am Encountering is when I do rsaJsonWebKey.toJson(OutputControlLevel.INCLUDE_PRIVATE)

I get this error:

java.lang.ClassCastException: sun.security.mscapi.RSAPrivateKey cannot be cast to java.security.interfaces.RSAPrivateKey at org.jose4j.jwk.RsaJsonWebKey.getRsaPrivateKey(RsaJsonWebKey.java:123) at org.jose4j.jwk.RsaJsonWebKey.fillPrivateTypeSpecificParams(RsaJsonWebKey.java:135) at org.jose4j.jwk.PublicJsonWebKey.fillTypeSpecificParams(PublicJsonWebKey.java:122) at org.jose4j.jwk.JsonWebKey.toParams(JsonWebKey.java:166) at org.jose4j.jwk.JsonWebKey.toJson(JsonWebKey.java:178) I tried to debug the code in Jose and the error is in PublicJsonWebKey class this line:

protected void fillPrivateTypeSpecificParams(Map<String,Object> params) { RSAPrivateKey rsaPrivateKey = getRsaPrivateKey(); rsaPrivateKey is java.security.interfaces.RSAPrivateKey while getRsaPrivateKey() returns org.jose4j.jwk.RsaJsonWebKey

What am I doing wrong?

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