关于 Des加密（Android与ios 与后台java服务器之间的加密解密）

最近做了一个移动项目，是有服务器和客户端类型的项目，客户端是要登录才行的，登录的密码要用DES加密，服务器是用Java开发的，客户端要同时支持多平台（Android、iOS），在处理iOS的DES加密的时候遇到了一些问题，起初怎么调都调不成和Android端生成的密文相同。最终一个忽然的想法让我找到了问题的所在，现在将代码总结一下，以备自己以后查阅。

首先，Java端的DES加密的实现方式，代码如下：

1 public class DES {

 2     private static byte[] iv = { 1, 2, 3, 4, 5, 6, 7, 8 };

 3 

 4     public static String encryptDES(String encryptString, String encryptKey)

 5             throws Exception {

 6         IvParameterSpec zeroIv = new IvParameterSpec(iv);

 7         SecretKeySpec key = new SecretKeySpec(encryptKey.getBytes(), "DES");

 8         Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");

 9         cipher.init(Cipher.ENCRYPT_MODE, key, zeroIv);

10         byte[] encryptedData = cipher.doFinal(encryptString.getBytes());

11         return Base64.encode(encryptedData);

12     }

13 }

上述代码用到了一个Base64的编码类，其代码的实现方式如下：

1 public class Base64 {

 2     private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

 3             .toCharArray();

 4 

 5     

11     public static String encode(byte[] data) {

12         int start = 0;

13         int len = data.length;

14         StringBuffer buf = new StringBuffer(data.length * 3 / 2);

15 

16         int end = len - 3;

17         int i = start;

18         int n = 0;

19 

20         while (i <= end) {

21             int d = ((((int) data[i]) & 0x0ff) << 16)

22                     | ((((int) data[i + 1]) & 0x0ff) << 8)

23                     | (((int) data[i + 2]) & 0x0ff);

24 

25             buf.append(legalChars[(d >> 18) & 63]);

26             buf.append(legalChars[(d >> 12) & 63]);

27             buf.append(legalChars[(d >> 6) & 63]);

28             buf.append(legalChars[d & 63]);

29 

30             i += 3;

31 

32             if (n++ >= 14) {

33                 n = 0;

34                 buf.append(" ");

35             }

36         }

37 

38         if (i == start + len - 2) {

39             int d = ((((int) data[i]) & 0x0ff) << 16)

40                     | ((((int) data[i + 1]) & 255) << 8);

41 

42             buf.append(legalChars[(d >> 18) & 63]);

43             buf.append(legalChars[(d >> 12) & 63]);

44             buf.append(legalChars[(d >> 6) & 63]);

45             buf.append("=");

46         } else if (i == start + len - 1) {

47             int d = (((int) data[i]) & 0x0ff) << 16;

48 

49             buf.append(legalChars[(d >> 18) & 63]);

50             buf.append(legalChars[(d >> 12) & 63]);

51             buf.append("==");

52         }

53 

54         return buf.toString();

55     }

56 ｝

以上便是Java端的DES加密方法的全部实现过程。

我还编写了一个将byte的二进制转换成16进制的方法，以便调试的时候使用打印输出加密后的byte数组的内容，这个方法不是加密的部分，只是为调试而使用的：

1       

 5     public static String parseByte2HexStr(byte buf[]) {  

 6             StringBuffer sb = new StringBuffer();  

 7             for (int i = 0; i < buf.length; i++) {  

 8                     String hex = Integer.toHexString(buf[i] & 0xFF);  

 9                     if (hex.length() == 1) {  

10                             hex = '0' + hex;  

11                     }  

12                     sb.append(hex.toUpperCase());  

13             }  

14             return sb.toString();  

15     }

下面是Objective-c在iOS上实现的DES加密算法:

1 static Byte iv[] = {1,2,3,4,5,6,7,8};

 2 +(NSString *) encryptUseDES:(NSString *)plainText key:(NSString *)key

 3 {

 4     NSString *ciphertext = nil;

 5     const char *textBytes = [plainText UTF8String];

 6     NSUInteger dataLength = [plainText length];

 7     unsigned char buffer[1024];

 8     memset(buffer, 0, sizeof(char));

 9     size_t numBytesEncrypted = 0;

10     CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmDES,

11                                           kCCOptionPKCS7Padding,

12                                           [key UTF8String], kCCKeySizeDES,

13                                           iv,

14                                           textBytes, dataLength,

15                                           buffer, 1024,

16                                           &numBytesEncrypted);

17     if (cryptStatus == kCCSuccess) {

18         NSData *data = [NSData dataWithBytes:buffer length:(NSUInteger)numBytesEncrypted];

19         ciphertext = [data base64Encoding];

20     }

21     return ciphertext;

22 }

下面是一个关键的类：NSData的Category实现，关于Category的实现网上很多说明不再讲述。

1 static const char encodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

 2 - (NSString *)base64Encoding;

 3 {

 4     if (self.length == 0)

 5         return @"";

 6     

 7     char *characters = malloc(self.length*3/2);

 8     

 9     if (characters == NULL)

10         return @"";

11     

12     int end = self.length - 3;

13     int index = 0;

14     int charCount = 0;

15     int n = 0;

16     

17     while (index <= end) {

18         int d = (((int)(((char *)[self bytes])[index]) & 0x0ff) << 16) 

19         | (((int)(((char *)[self bytes])[index + 1]) & 0x0ff) << 8)

20         | ((int)(((char *)[self bytes])[index + 2]) & 0x0ff);

21         

22         characters[charCount++] = encodingTable[(d >> 18) & 63];

23         characters[charCount++] = encodingTable[(d >> 12) & 63];

24         characters[charCount++] = encodingTable[(d >> 6) & 63];

25         characters[charCount++] = encodingTable[d & 63];

26         

27         index += 3;

28         

29         if(n++ >= 14)

30         {

31             n = 0;

32             characters[charCount++] = ' ';

33         }

34     }

35     

36     if(index == self.length - 2)

37     {

38         int d = (((int)(((char *)[self bytes])[index]) & 0x0ff) << 16) 

39         | (((int)(((char *)[self bytes])[index + 1]) & 255) << 8);

40         characters[charCount++] = encodingTable[(d >> 18) & 63];

41         characters[charCount++] = encodingTable[(d >> 12) & 63];

42         characters[charCount++] = encodingTable[(d >> 6) & 63];

43         characters[charCount++] = '=';

44     }

45     else if(index == self.length - 1)

46     {

47         int d = ((int)(((char *)[self bytes])[index]) & 0x0ff) << 16;

48         characters[charCount++] = encodingTable[(d >> 18) & 63];

49         characters[charCount++] = encodingTable[(d >> 12) & 63];

50         characters[charCount++] = '=';

51         characters[charCount++] = '=';

52     }

53     NSString * rtnStr = [[NSString alloc] initWithBytesNoCopy:characters length:charCount encoding:NSUTF8StringEncoding freeWhenDone:YES];

54     return rtnStr;

55 }

这个方法和java端的那个Base64的encode方法基本上是一个算法，只是根据语言的特点不同有少许的改动。

下面也是Objective-c的一个二进制转换为16进制的方法，也是为了测试方便查看写的：

1 +(NSString *) parseByte2HexString:(Byte *) bytes

 2 {

 3     NSMutableString *hexStr = [[NSMutableString alloc]init];

 4     int i = 0;

 5     if(bytes)

 6     {

 7         while (bytes[i] != '\0') 

 8         {

 9             NSString *hexByte = [NSString stringWithFormat:@"%x",bytes[i] & 0xff];///16进制数
10             if([hexByte length]==1)

11                 [hexStr appendFormat:@"0%@", hexByte];

12             else 

13                 [hexStr appendFormat:@"%@", hexByte];

14             

15             i++;

16         }

17     }

18     NSLog(@"bytes 的16进制数为:%@",hexStr);

19     return hexStr;

20 }

21 

22 +(NSString *) parseByteArray2HexString:(Byte[]) bytes

23 {

24     NSMutableString *hexStr = [[NSMutableString alloc]init];

25     int i = 0;

26     if(bytes)

27     {

28         while (bytes[i] != '\0') 

29         {

30             NSString *hexByte = [NSString stringWithFormat:@"%x",bytes[i] & 0xff];///16进制数
31             if([hexByte length]==1)

32                 [hexStr appendFormat:@"0%@", hexByte];

33             else 

34                 [hexStr appendFormat:@"%@", hexByte];

35 

36             i++;

37         }

38     }

39     NSLog(@"bytes 的16进制数为:%@",hexStr);

40     return hexStr;

41 }

以上的加密方法所在的包是CommonCrypto/CommonCryptor.h。

以上便实现了Objective-c和Java下在相同的明文和密钥的情况下生成相同明文的算法。

Base64的算法可以用你们自己写的那个，不一定必须使用我提供的这个。解密的时候还要用Base64进行密文的转换。



我的解密算法如下：

1 　　private static byte[] iv = { 1, 2, 3, 4, 5, 6, 7, 8 };    

 2 　　public static String decryptDES(String decryptString, String decryptKey)

 3             throws Exception {

 4         byte[] byteMi = Base64.decode(decryptString);

 5         IvParameterSpec zeroIv = new IvParameterSpec(iv);

 6         SecretKeySpec key = new SecretKeySpec(decryptKey.getBytes(), "DES");

 7         Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");

 8         cipher.init(Cipher.DECRYPT_MODE, key, zeroIv);

 9         byte decryptedData[] = cipher.doFinal(byteMi);

10 

11         return new String(decryptedData);

12     }

Base64的decode方法如下：

1 　　public static byte[] decode(String s) {

 2 

 3         ByteArrayOutputStream bos = new ByteArrayOutputStream();

 4         try {

 5             decode(s, bos);

 6         } catch (IOException e) {

 7             throw new RuntimeException();

 8         }

 9         byte[] decodedBytes = bos.toByteArray();

10         try {

11             bos.close();

12             bos = null;

13         } catch (IOException ex) {

14             System.err.println("Error while decoding BASE64: " + ex.toString());

15         }

16         return decodedBytes;

17     }

18     private static void decode(String s, OutputStream os) throws IOException {

19         int i = 0;

20 

21         int len = s.length();

22 

23         while (true) {

24             while (i < len && s.charAt(i) <= ' ')

25                 i++;

26 

27             if (i == len)

28                 break;

29 

30             int tri = (decode(s.charAt(i)) << 18)

31                     + (decode(s.charAt(i + 1)) << 12)

32                     + (decode(s.charAt(i + 2)) << 6)

33                     + (decode(s.charAt(i + 3)));

34 

35             os.write((tri >> 16) & 255);

36             if (s.charAt(i + 2) == '=')

37                 break;

38             os.write((tri >> 8) & 255);

39             if (s.charAt(i + 3) == '=')

40                 break;

41             os.write(tri & 255);

42 

43             i += 4;

44         }

45     }

46     private static int decode(char c) {

47         if (c >= 'A' && c <= 'Z')

48             return ((int) c) - 65;

49         else if (c >= 'a' && c <= 'z')

50             return ((int) c) - 97 + 26;

51         else if (c >= '0' && c <= '9')

52             return ((int) c) - 48 + 26 + 26;

53         else

54             switch (c) {

55             case '+':

56                 return 62;

57             case '/':

58                 return 63;

59             case '=':

60                 return 0;

61             default:

62                 throw new RuntimeException("unexpected code: " + c);

63             }

64     }

以上便实现了DES加密后的密文的解密。

Java端的测试代码如下：

1     String plaintext = "abcd";

2     String ciphertext = DES.encryptDES(plaintext, "20120401");

3     System.out.println("明文：" + plaintext);

4     System.out.println("密钥：" + "20120401");

5     System.out.println("密文：" + ciphertext);

6     System.out.println("解密后：" + DES.decryptDES(ciphertext, "20120401"));

输出结果：

明文：abcd

密钥：20120401

密文：W7HR43/usys=

解密后：abcd

Objective-c端的测试代码如下：

1     NSString *plaintext = @"abcd";

2     NSString *ciphertext = [EncryptUtil encryptUseDES:plaintext key:@"20120401"];

3     NSLog(@"明文：%@",plaintext);

4     NSLog(@"秘钥：%@",@"20120401");

5     NSLog(@"密文：%@",ciphertext);

输出结果：

1 2012-04-05 12:00:47.348 TestEncrypt[806:f803] 明文：abcd

2 2012-04-05 12:00:47.350 TestEncrypt[806:f803] 秘钥：20120401

3 2012-04-05 12:00:47.350 TestEncrypt[806:f803] 密文：W7HR43/usys=