import org.bouncycastle.openssl.PEMParser;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import java.io.StringReader;
import java.util.Base64;
import java.security.interfaces.RSAPublicKey;
import java.security.Signature;
import java.security.spec.PSSParameterSpec;
import java.security.spec.MGF1ParameterSpec;
import java.security.MessageDigest;

public class MyTest
{
    public static void main(String[] args) throws Exception
    {
        String plaintext = "zzz";
        String signature = "JwqW/Xhh1hFxP5pGJAKkdVM+6WZ5FtQuPdwlmDq+pmJXknIybW4f31w7lJiBvc2VL8fNXg1DllwuwyCnErKRSygDGwdzkHJ/chvrjUequhiqoPhgKe3vQCFvJdlbeUEkF2Ho2qK5xU0VI3ViS1htDuQXJvCHm30wO+zgW9kshCE=";

        String key = "-----BEGIN RSA PUBLIC KEY-----\n" +
"MIGJAoGBAM5iHBWEep6wz0o6PrD0MdmjuO2SJivi0Ik01eFZn3GuyEpUvMI1eLtH\n" +
"77wFORzI2eQTc2sGYWctEZk4k/Im91TFW0ahYyeB2m1XQ/cSY8RO9nyrWiGPJjzI\n" +
"FuePuh8dqWHT2hGDfD9CmMmz7Zb+fltmSZ3siF9XbWyUTnemQpOtAgMBAAE=\n" +
"-----END RSA PUBLIC KEY-----\n";

        // load the public key
        PEMParser pemParser = new PEMParser(new StringReader(key));
        JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
        SubjectPublicKeyInfo pub = SubjectPublicKeyInfo.getInstance(pemParser.readObject());
        RSAPublicKey publicKey = (RSAPublicKey) converter.getPublicKey(pub);

        // load the plaintext
        byte[] signatureBytes = Base64.getDecoder().decode(signature);

        // perform the actual signature verification
        Signature sig = Signature.getInstance("RSASSA-PSS");
        PSSParameterSpec pssParams = new PSSParameterSpec(
            "SHA-256",
            "MGF1",
            new MGF1ParameterSpec("SHA-1"),
            MessageDigest.getInstance("SHA-256").getDigestLength(),
            PSSParameterSpec.TRAILER_FIELD_BC
        );
        sig.setParameter(pssParams);

        sig.initVerify(publicKey);
        sig.update(plaintext.getBytes());
        System.out.println(sig.verify(signatureBytes) ? "good" : "bad");
    }
}