RsaDecryptor.java

import org.springframework.stereotype.Component;

import javax.crypto.Cipher;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.security.KeyPair;
import java.util.Base64;

import static java.nio.charset.StandardCharsets.ISO_8859_1;

@Component
public class RsaDecryptor implements Decryptor {

    public static final String RSA = "RSA";

    private final KeyPair keyPair;

    public RsaDecryptor(KeyPair keyPair) {
        this.keyPair = keyPair;
    }

    @Override
    public InputStream decrypt(String encryptedText) {
        try {
            byte[] encryptedData = encryptedText.getBytes(ISO_8859_1);
            byte[] decodedData = Base64.getDecoder().decode(encryptedData);
            Cipher cipher = Cipher.getInstance(RsaDecryptor.RSA);
            cipher.init(Cipher.DECRYPT_MODE, keyPair.getPrivate());
            byte[] decryptedData = cipher.doFinal(decodedData);
            return new ByteArrayInputStream(decryptedData);
        } catch (Exception e) {
            throw new DecryptionException("Couldn't decrypt the text: " + encryptedText + ", cause: " + e.toString(), e);
        }
    }
}