Android RSA解密

目前项目有一个后台是使用RSA公钥加密，而后台给我的私钥是字符串， 请问如何把后台给的是要的字符串转换成PrivateKey

得看看是什么样的字符串啊。PrivateKey本身也会转化成字符串。文件的会分cer和pem还有key的。另外还要看语言，没有这些信息没办法转换的。

我贴一个demo，供参考：

 import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.NoSuchPaddingException;
import java.io.*;
import java.security.*;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;

public class PrivateKeyTest {

    /**
     * 根据私钥字符串生成私钥对象
     */
    private static void test1() throws InvalidKeySpecException, NoSuchAlgorithmException {
        byte[] bytes = "xxxx".getBytes();
        PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(bytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
    }

    /**
     * 1、随机生成一个秘钥对
     * 2、加密
     * 3、解密
     */
    private static void test2() throws NoSuchAlgorithmException, NoSuchPaddingException, IOException, InvalidKeyException {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(1024);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        String text = "abcdefghijklmn";

        // 加密
        Cipher encryptCipher = Cipher.getInstance("RSA");
        encryptCipher.init(Cipher.ENCRYPT_MODE, keyPair.getPrivate());
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        CipherOutputStream cipherOutputStream = new CipherOutputStream(byteArrayOutputStream, encryptCipher);
        DataOutputStream dataOutputStream = new DataOutputStream(cipherOutputStream);
        dataOutputStream.writeUTF(text);
        dataOutputStream.flush();
        dataOutputStream.close();
        byte[] cipherTextData = byteArrayOutputStream.toByteArray();

        // 解密
        Cipher decryptCipher = Cipher.getInstance("RSA");
        decryptCipher.init(Cipher.DECRYPT_MODE, keyPair.getPublic());
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(cipherTextData);
        CipherInputStream cipherInputStream = new CipherInputStream(byteArrayInputStream, decryptCipher);
        DataInputStream dataInputStream = new DataInputStream(cipherInputStream);
        String result = dataInputStream.readUTF();
        dataInputStream.close();
        System.out.println("result = " + result);
    }

    public static void main(String[] args) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, IOException {
        test2();
    }

}