JWK jwk = jwkEntry.getValue();
if (jwk instanceof RSAKey) {
// build RSA encrypters and decrypters
RSAEncrypter encrypter = new RSAEncrypter(((RSAKey) jwk).toRSAPublicKey()); // there should always at least be the public key
encrypters.put(id, encrypter);
if (jwk.isPrivate()) { // we can decrypt!
RSADecrypter decrypter = new RSADecrypter(((RSAKey) jwk).toRSAPrivateKey());
decrypters.put(id, decrypter);