Flutter RSA加密、解密之我见一

1、需要公钥和私钥

公钥内容:

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC+XpiP5bcOmzgOHG0eRDVx41kP
ECiMCx14KduElU53kCyY02xETFC/KxF8mpFCEM9b8iTSAKjRbAs8CXQtSJIxv9d9
/a6OhXKg6WadljRmVoZZm9MD2MGixMGYN2W3noEkfUHeWUtghk8ohcAMdl4mwanm
+JBAkTEOsVlegk/27QIDAQAB
-----END PUBLIC KEY-----

私钥内容:

-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----

为了方便使用我们可以把他们放到两个不同文件中

2、导入依赖

encrypt: ^4.0.0

3、导入头文件

import 'package:flutter/services.dart' show rootBundle;
import 'package:encrypt/encrypt.dart';

4、代码实现一

加密实现:

  static Future<String> encodeString(String content) async{
    var publicKeyStr = await rootBundle.loadString('assets/data/rsa_public_key.pem');
    var publicKey = RSAKeyParser().parse(publicKeyStr);
    final encrypter = Encrypter(RSA(publicKey: publicKey));     
    return await encrypter.encrypt(content).base64.toUpperCase();
  }

解密实现:

  static Future<String> decodeString(String content) async{
    var publicKeyStr = await rootBundle.loadString('assets/data/rsa_private_key.pem');
    var publicKey =  RSAKeyParser().parse(publicKeyStr);
    final encrypter = Encrypter(RSA(publicKey: publicKey));     
    return await encrypter.decrypt(Encrypted.fromBase64(content));
  }

细心的朋友会发现当我们的当字符串长度超过117，这时候会报溢出。我们来继续完善我们的代码，也就是说字符串长度超过117就需要做分段加密 和分段解密。

5、代码实现二

分段加密实现:

  static Future<String> encodeString(String content) async{
    var publicKeyStr = await rootBundle.loadString('assets/data/rsa_public_key.pem');
    var publicKey = RSAKeyParser().parse(publicKeyStr);
    final encrypter = Encrypter(RSA(publicKey: publicKey));

    List<int> sourceBytes = utf8.encode(content);
    int inputLen = sourceBytes.length;
    int maxLen = 117;
    List<int> totalBytes = List();
    for (var i = 0; i < inputLen; i += maxLen) {
      int endLen = inputLen - i;
      List<int> item;
      if (endLen > maxLen) {
        item = sourceBytes.sublist(i, i + maxLen);
      }
      else {
        item = sourceBytes.sublist(i, i + endLen);
      }
      totalBytes.addAll(encrypter.encryptBytes(item).bytes);
    }
    return base64.encode(totalBytes);
//       return await encrypter.encrypt(content).base64.toUpperCase();
  }

分段解密实现:

  static Future<String> decodeString(String content) async{
    var publicKeyStr = await rootBundle.loadString('assets/data/rsa_private_key.pem');
    var publicKey =  RSAKeyParser().parse(publicKeyStr);
    final encrypter = Encrypter(RSA(publicKey: publicKey));

    Uint8List sourceBytes = base64.decode(content);
    int inputLen = sourceBytes.length;
    int maxLen = 128;
    List<int> totalBytes = List();
    for (var i = 0; i < inputLen; i += maxLen) {
      int endLen = inputLen - i;
      Uint8List item;
      if (endLen > maxLen) {
        item = sourceBytes.sublist(i, i + maxLen);
      } else {
        item = sourceBytes.sublist(i, i + endLen);
      }
      totalBytes.addAll(encrypter.decryptBytes(Encrypted(item)));
    }
    return utf8.decode(totalBytes);
//        return await encrypter.decrypt(Encrypted.fromBase64(content));
  }

6、代码调用

String encode = await MyEncrypt.encodeString(jsonString);
print("encode:$encode");
String decode = await MyEncrypt.decodeString(encode);
print("decode:$decode");

7、问题深究

现实中经常出现
上传数据：客户端使用公钥加密，服务端使用私钥解密；
下发数据: 服务端使用私钥加密，客户端使用公钥解密。
这时候我们需要怎么处理呢?答案在下一篇。

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Flutter RSA加密、解密之我见二