Android：使用存储在文件中的公钥解密RSA文本

Question

我试了好几天都没有成功。

在StackOverflow中有很多类似的问题，甚至有两个问题与我的问题完全相同，但没有得到回答和解决：1）将PHP RSA公钥转换为Android公钥；2）Android：如何用RSA密钥解密openssl加密文件？

我看到了很多关于如何解密RSA文本的示例，如下所示：

public static byte[] decryptRSA( PublicKey key, byte[] text) throws Exception
      { 
          byte[] dectyptedText = null;

          Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
          cipher.init(Cipher.DECRYPT_MODE, key);
          dectyptedText = cipher.doFinal(text);
          return dectyptedText;
      }

    InputStream is = getResources().openRawResource(R.raw.public);
    DataInputStream dis = new DataInputStream(is);
    byte [] keyBytes = new byte [(int) is.available()];
    dis.readFully(keyBytes);
    dis.close();
    X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    return keyFactory.generatePublic(spec);

Answer 1

终于解决了！！！鼓声、号角声和美妙的交响乐！！！

public static byte[] decryptRSA(Context mContext, byte[] message) throws Exception { 

    // reads the public key stored in a file
    InputStream is = mContext.getResources().openRawResource(R.raw.sm_public);
    BufferedReader br = new BufferedReader(new InputStreamReader(is));
    List<String> lines = new ArrayList<String>();
    String line = null;
    while ((line = br.readLine()) != null)
        lines.add(line);

    // removes the first and last lines of the file (comments)
    if (lines.size() > 1 && lines.get(0).startsWith("-----") && lines.get(lines.size()-1).startsWith("-----")) {
        lines.remove(0);
        lines.remove(lines.size()-1);
    }

    // concats the remaining lines to a single String
    StringBuilder sb = new StringBuilder();
    for (String aLine: lines)
        sb.append(aLine);
    String keyString = sb.toString();
    Log.d("log", "keyString:"+keyString);

    // converts the String to a PublicKey instance
    byte[] keyBytes = Base64.decodeBase64(keyString.getBytes("utf-8"));
    X509EncodedKeySpec spec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PublicKey key = keyFactory.generatePublic(spec);

    // decrypts the message
    byte[] dectyptedText = null;
    Cipher cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.DECRYPT_MODE, key);
    dectyptedText = cipher.doFinal(Base64.decodeBase64(message));
    return dectyptedText;
}

解决方案是Base64不仅解码从文件中读取的公钥，而且解码加密的消息本身！

顺便说一下，我按照@Nikolay建议的方式从文件中读取公钥（又是tnx男）。