Create PublicKey object using public key generated from pre-Ruby 1.9.3 and SpongyCastle

gistfile1.java

import java.io.IOException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPublicKeySpec;

import org.spongycastle.asn1.ASN1InputStream;
import org.spongycastle.asn1.DERObject;
import org.spongycastle.asn1.x509.RSAPublicKeyStructure;
import org.spongycastle.util.encoders.Base64;

public class RSAUtil {
    static public PublicKey publicKey(String publicKeyString) {
        try {
            byte[] decodedPublicKey = Base64.decode(publicKeyString);
            ASN1InputStream in = new ASN1InputStream(decodedPublicKey);
            DERObject obj = in.readObject();
            RSAPublicKeyStructure keyStruct = RSAPublicKeyStructure.getInstance(obj);
            RSAPublicKeySpec keySpec = new RSAPublicKeySpec(keyStruct.getModulus(), keyStruct.getPublicExponent());
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            return keyFactory.generatePublic(keySpec);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (InvalidKeySpecException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}