How to use Android keystore and BouncyCastle for Sign Operation Implementation using RSA-PSS

usingBouncyCastleForDigitalSignImplementation.java

/*
*	If you use this primitive to implement, for example, Bouncy Castle's 
*	AsymmetricBlockCipher interface, you can use any signature algorithm available in the 
*	Bouncy Castle lightweight API (we actually use Spongy Castle to stay compatible 
*	with Android 2.x without too much hastle). 
*	For example, if you want to use a more modern (and provably secure) 
*	signature algorithm than Android's default PKCS#1.5
*	implementation, such as RSA-PSS you can accomplish it with something 
*	like this (see sample project for AndroidRsaEngine):
*/

AndroidRsaEngine rsa = new AndroidRsaEngine("key1", true);

Digest digest = new SHA512Digest();
Digest mgf1digest = new SHA512Digest();
PSSSigner signer = new PSSSigner(rsa, digest, mgf1digest, 512 / 8);
RSAKeyParameters params = new RSAKeyParameters(false,
                    pubKey.getModulus(), pubKey.getPublicExponent());

signer.init(true, params);
signer.update(signedData, 0, signedData.length);
byte[] signature = signer.generateSignature();