usingRSAPrivateKeyForDataEncryption.java

/*
 * By using the IKeyStoreService directly you can store symmetric keys or other secret data
 * in the system key store by using the put() method, which the current java.security.KeyStore implementation
 * does not allow (it can only store PrivateKey's). Such data is only encrypted 
 * by the key store master key, and even the system key store is hardware-backed, 
 * data is not protected by hardware in any way.
 * 
 * Accessing hidden services is not the only way to augment the system key store functionality.
 * Since the sign() operation implements a 'raw' signature operation (RSASP1 in RFC 3447), 
 * key store-managed (including hardware-backed) keys can be used to 
 * implement signature algorithms not natively supported by Android. 
 * You don't need to use the IKeyStoreService interface, because 
 * this operation is available through the standard JCE Cipher interface: 
*/

KeyStore ks = KeyStore.getInstance("AndroidKeyStore");
ks.load(null);
KeyStore.Entry keyEntry = keyStore.getEntry("key1", null);
RSAPrivteKey privKey = (RSAPrivateKey)  keyEntry.getPrivateKey();

Cipher c = Cipher.getInstance("RSA/ECB/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, i privateKey);
// suppose {in} as a symmetric key material which is going to be protected using rsa public key encryption
byte[] result = cipher.doFinal(in, o, in.length);