Using ssh-keygen generated id_rsa to encrypt/decrypt text

TrySshKeyEncryptDecrypt.java

package app;

import com.sshtools.common.publickey.InvalidPassphraseException;
import com.sshtools.common.publickey.SshKeyUtils;
import com.sshtools.common.ssh.SshException;
import com.sshtools.common.ssh.components.SshKeyPair;
import com.sshtools.common.ssh.components.SshPrivateKey;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.NoSuchPaddingException;

public class TrySshKeyEncryptDecrypt {

    public static void main(String[] args)
        throws IOException, InvalidPassphraseException, SshException, NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, NoSuchProviderException {

        final Path idRsaFile;
        if (args.length > 0) {
            idRsaFile = Paths.get(args[0]);
        }
        else {
            idRsaFile = Paths.get(System.getProperty("user.home"), ".ssh", "id_rsa");
        }

        // throws InvalidPassphraseException is a passphrase was used on private key file
        final SshKeyPair keyPair = SshKeyUtils.getPrivateKey(idRsaFile.toFile(), null);
        System.out.printf("Loaded private key for fingerprint %s%n", keyPair.getPublicKey().getFingerprint());

        final String cipherText = encrypt(keyPair, "this is a test");
        System.out.println(cipherText);

        final String clearText = decrypt(keyPair, cipherText);
        System.out.println(clearText);
    }

    private static String decrypt(SshKeyPair keyPair, String cipherText)
        throws NoSuchPaddingException, NoSuchAlgorithmException, NoSuchProviderException, InvalidKeyException, IOException {
        final Cipher cipher = Cipher.getInstance("RSA/ECB/NoPadding", "BC");
        cipher.init(Cipher.DECRYPT_MODE, keyPair.getPrivateKey().getJCEPrivateKey());

        final ByteArrayInputStream bytesIn = new ByteArrayInputStream(
            Base64.getUrlDecoder().decode(cipherText)
        );
        final CipherInputStream cipherIn = new CipherInputStream(bytesIn, cipher);
        return new String(cipherIn.readAllBytes(), StandardCharsets.UTF_8);
    }

    private static String encrypt(SshKeyPair keyPair, String s)
        throws NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException, InvalidKeyException, IOException {
        final Cipher cipher = Cipher.getInstance("RSA/ECB/NoPadding", "BC");
        cipher.init(Cipher.ENCRYPT_MODE, keyPair.getPublicKey().getJCEPublicKey());

        final ByteArrayOutputStream bytesOut = new ByteArrayOutputStream();
        final CipherOutputStream cipherOut = new CipherOutputStream(bytesOut, cipher);
        cipherOut.write(s.getBytes(StandardCharsets.UTF_8));
        cipherOut.flush();
        cipherOut.close();

        return Base64.getUrlEncoder().encodeToString(bytesOut.toByteArray());
    }

}