├── FileEnDecryptManager.java
└── README.md


/FileEnDecryptManager.java:
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  1 | import java.io.File;
  2 | import java.io.IOException;
  3 | import java.io.RandomAccessFile;
  4 | import java.nio.MappedByteBuffer;
  5 | import java.nio.channels.FileChannel;
  6 | 
  7 | /**
  8 |  * Created by IntelliJ IDEA.
  9 |  * Author:Eric
 10 |  * Date:2015/1/14
 11 |  * Desc:加密解密管理类
 12 |  * 加密算法 : 将文件的数据流的每个字节与加密解密key对应字符做异或运算.
 13 |  * 解密算法 : 已经加密的文件再执行一次对文件的数据流的每个字节与加密解密key对应字符做异或运算.
 14 |  * this method can decrypt or encrypt a large file in 100 milliseconds,just have a try and see
 15 |  */
 16 | public class FileEnDecryptManager {
 17 | 
 18 |     private String key = "abcdefg"; // 加密解密key(Encrypt or decrypt key)
 19 | 
 20 |     private FileEnDecryptManager() {
 21 |     }
 22 | 
 23 |     private static FileEnDecryptManager instance = null;
 24 | 
 25 |     public static FileEnDecryptManager getInstance() {
 26 |         synchronized (FileEnDecryptManager.class) {
 27 |             if (instance == null) {
 28 |                 instance = new FileEnDecryptManager();
 29 |             }
 30 |         }
 31 |         return instance;
 32 |     }
 33 | 
 34 |     /**
 35 |      * 加密入口(encrypt intrance)
 36 |      *
 37 |      * @param fileUrl 文件绝对路径
 38 |      * @return
 39 |      */
 40 |     public boolean doEncrypt(String fileUrl) {
 41 |         try {
 42 |             if (isDecrypted(fileUrl)) {
 43 |                 if (encrypt(fileUrl)) {
 44 |                     // 可在此处保存加密状态到数据库或文件(you can save state into db or file)
 45 |                     LogUtils.d("encrypt succeed");
 46 |                     return true;
 47 |                 } else {
 48 |                     LogUtils.d("encrypt failed");
 49 |                     return false;
 50 |                 }
 51 |             }
 52 |         } catch (IOException e) {
 53 |             e.printStackTrace();
 54 |         }
 55 |         return false;
 56 |     }
 57 | 
 58 |     private final int REVERSE_LENGTH = 28; // 加解密长度(Encryption length)
 59 | 
 60 |     /**
 61 |      * 加解密(Encrypt or deprypt method)
 62 |      *
 63 |      * @param strFile 源文件绝对路径
 64 |      * @return
 65 |      */
 66 |     private boolean encrypt(String strFile) {
 67 |         int len = REVERSE_LENGTH;
 68 |         try {
 69 |             File f = new File(strFile);
 70 |             if (f.exists()) {
 71 |                 RandomAccessFile raf = new RandomAccessFile(f, "rw");
 72 |                 long totalLen = raf.length();
 73 | 
 74 |                 if (totalLen < REVERSE_LENGTH)
 75 |                     len = (int) totalLen;
 76 | 
 77 |                 FileChannel channel = raf.getChannel();
 78 |                 MappedByteBuffer buffer = channel.map(
 79 |                         FileChannel.MapMode.READ_WRITE, 0, REVERSE_LENGTH);
 80 |                 byte tmp;
 81 |                 for (int i = 0; i < len; ++i) {
 82 |                     byte rawByte = buffer.get(i);
 83 |                     if (i <= key.length() - 1) {
 84 |                         tmp = (byte) (rawByte ^ key.charAt(i)); // 异或运算(XOR operation)
 85 |                     } else {
 86 |                         tmp = (byte) (rawByte ^ i);
 87 |                     }
 88 |                     buffer.put(i, tmp);
 89 |                 }
 90 |                 buffer.force();
 91 |                 buffer.clear();
 92 |                 channel.close();
 93 |                 raf.close();
 94 |                 return true;
 95 |             }
 96 |         } catch (Exception e) {
 97 |             e.printStackTrace();
 98 |         }
 99 |         return false;
100 |     }
101 | 
102 |     /**
103 |      * 解密入口(decrypt intrance)
104 |      *
105 |      * @param fileUrl 源文件绝对路径
106 |      */
107 |     public void doDecrypt(String fileUrl) {
108 |         try {
109 |             if (!isDecrypted(fileUrl)) {
110 |                 decrypt(fileUrl);
111 |             }
112 |         } catch (Exception e) {
113 |             e.printStackTrace();
114 |         }
115 |     }
116 | 
117 |     private void decrypt(String fileUrl) {
118 |         if (encrypt(fileUrl)) {
119 |             // 可在此处保存解密状态到数据库或文件(you can save state into db or file)
120 |             LogUtils.d("decrypt succeed");
121 |         }
122 |     }
123 | 
124 |     /**
125 |      * fileName 文件是否已经解密了(Whether file has been decrypted)
126 |      *
127 |      * @param filePath
128 |      * @return
129 |      * @throws IOException
130 |      */
131 |     private boolean isDecrypted(String filePath) throws IOException {
132 |         // 从数据库或者文件中取出此路径对应的状态(get state out from db or file)
133 |     }
134 | }
135 | 


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/README.md:
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1 | # Android-File-Encrypt
2 | Encrypt and decrypt files in android or java
3 | 
4 | #Encrypt
5 | FileEnDecryptManager.getInstance().doEncrypt(filePath);
6 | 
7 | #Decrypt
8 | FileEnDecryptManager.getInstance().doDecrypt(filePath);
9 | 


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