Objective-C 和 Java 下 DES加解密保持一致的方式

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：

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

public static String encryptDES(String encryptString, String encryptKey) throws Exception
{
IvParameterSpec zeroIv = new IvParameterSpec(iv);
SecretKeySpec key = new SecretKeySpec(encryptKey.getBytes(), "DES");
Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key, zeroIv);
byte[] encryptedData = cipher.doFinal(encryptString.getBytes());
return Base64.encode(encryptedData);
}
}

上述代码用到了一个Base64的编码类，其代码的实现方式如下：

public class Base64 {
private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

/**
* data[]进行编码
*
* @param data
* @return
*/
public static String encode(byte[] data) {
int start = 0;
int len = data.length;
StringBuffer buf = new StringBuffer(data.length * 3 / 2);

int end = len - 3;
int i = start;
int n = 0;

while (i <= end) {
int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 0x0ff) << 8) | (((int) data[i + 2]) & 0x0ff);

buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append(legalChars[(d >> 6) & 63]);
buf.append(legalChars[d & 63]);

i += 3;

if (n++ >= 14) {
n = 0;
buf.append(" ");
}
}

if (i == start + len - 2) {
int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 255) << 8);

buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append(legalChars[(d >> 6) & 63]);
buf.append("=");
}
else if (i == start + len - 1) {
int d = (((int) data[i]) & 0x0ff) << 16;

buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append("==");
}

return buf.toString();
}
}

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：

/**将二进制转换成16进制
* @param buf
* @return String
*/
public static String parseByte2HexStr(byte buf[])
{
StringBuffer sb = new StringBuffer();
for (int i = 0; i < buf.length; i++)
{
String hex = Integer.toHexString(buf[i] & 0xFF);
if (hex.length() == 1) {
hex = '0' + hex;
}
sb.append(hex.toUpperCase());
}
return sb.toString();
}

下面是Objective-c在iOS上实现的DES加密算法: 添加头文件#import

- (NSString *) encryptUseDES:(NSString *)plainText key:(NSString *)key
{
NSString *ciphertext = nil;
const char *textBytes = [plainText UTF8String];
NSUInteger dataLength = [plainText length];
unsigned char buffer[1024];
memset(buffer, 0, sizeof(char));
size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmDES,
kCCOptionPKCS7Padding,
[key UTF8String], kCCKeySizeDES,
iv,
textBytes, dataLength,
buffer, 1024,
&numBytesEncrypted);
if (cryptStatus == kCCSuccess) {
NSData *data = [NSData dataWithBytes:buffer length:(NSUInteger)numBytesEncrypted];

ciphertext = [data base64Encoding];
}
return ciphertext;
}

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。

static const char encodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
- (NSString *)base64Encoding;
{
if (self.length == 0)
return @"";

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

if (characters == NULL)
return @"";

int end = self.length - 3;
int index = 0;
int charCount = 0;
int n = 0;

while (index <= end) {
int d = (((int)(((char *)[self bytes])[index]) & 0x0ff) << 16)
| (((int)(((char *)[self bytes])[index + 1]) & 0x0ff) << 8)
| ((int)(((char *)[self bytes])[index + 2]) & 0x0ff);

characters[charCount++] = encodingTable[(d >> 18) & 63];
characters[charCount++] = encodingTable[(d >> 12) & 63];
characters[charCount++] = encodingTable[(d >> 6) & 63];
characters[charCount++] = encodingTable[d & 63];

index += 3;

if(n++ >= 14)
{
n = 0;
characters[charCount++] = ' ';
}
}

if(index == self.length - 2)
{
int d = (((int)(((char *)[self bytes])[index]) & 0x0ff) << 16)
| (((int)(((char *)[self bytes])[index + 1]) & 255) << 8);
characters[charCount++] = encodingTable[(d >> 18) & 63];
characters[charCount++] = encodingTable[(d >> 12) & 63];
characters[charCount++] = encodingTable[(d >> 6) & 63];
characters[charCount++] = '=';
}
else if(index == self.length - 1)
{
int d = ((int)(((char *)[self bytes])[index]) & 0x0ff) << 16;
characters[charCount++] = encodingTable[(d >> 18) & 63];
characters[charCount++] = encodingTable[(d >> 12) & 63];
characters[charCount++] = '=';
characters[charCount++] = '=';
}
NSString * rtnStr = [[NSString alloc] initWithBytesNoCopy:characters length:charCount encoding:NSUTF8StringEncoding freeWhenDone:YES];
return rtnStr;
}

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：

+(NSString *) parseByte2HexString:(Byte *) bytes
{
NSMutableString *hexStr = [[NSMutableString alloc]init];
int i = 0;
if(bytes)
{
while (bytes[i] != '\0')
{
NSString *hexByte = [NSString stringWithFormat:@"%x",bytes[i] & 0xff];///16进制数
if([hexByte length]==1)
[hexStr appendFormat:@"0%@", hexByte];
else
[hexStr appendFormat:@"%@", hexByte];

i++;
}
}
NSLog(@"bytes 的16进制数为:%@",hexStr);
return hexStr;
}

+(NSString *) parseByteArray2HexString:(Byte[]) bytes
{
NSMutableString *hexStr = [[NSMutableString alloc]init];
int i = 0;
if(bytes)
{
while (bytes[i] != '\0')
{
NSString *hexByte = [NSString stringWithFormat:@"%x",bytes[i] & 0xff];///16进制数
if([hexByte length]==1)
[hexStr appendFormat:@"0%@", hexByte];
else
[hexStr appendFormat:@"%@", hexByte];

i++;
}
}
NSLog(@"bytes 的16进制数为:%@",hexStr);
return hexStr;
}

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：

private static byte[] iv = { 1, 2, 3, 4, 5, 6, 7, 8 };
　public static String decryptDES(String decryptString, String decryptKey)
throws Exception {
byte[] byteMi = Base64.decode(decryptString);
IvParameterSpec zeroIv = new IvParameterSpec(iv);
SecretKeySpec key = new SecretKeySpec(decryptKey.getBytes(), "DES");
Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE, key, zeroIv);
byte decryptedData[] = cipher.doFinal(byteMi);

return new String(decryptedData);
}

Base64的decode方法如下：

public static byte[] decode(String s) {

ByteArrayOutputStream bos = new ByteArrayOutputStream();
try {
decode(s, bos);
} catch (IOException e) {
throw new RuntimeException();
}
byte[] decodedBytes = bos.toByteArray();
try {
bos.close();
bos = null;
} catch (IOException ex) {
System.err.println("Error while decoding BASE64: " + ex.toString());
}
return decodedBytes;
}
private static void decode(String s, OutputStream os) throws IOException {
int i = 0;

int len = s.length();

while (true) {
while (i < len && s.charAt(i) <= ' ')
i++;

if (i == len)
break;

int tri = (decode(s.charAt(i)) << 18)
+ (decode(s.charAt(i + 1)) << 12)
+ (decode(s.charAt(i + 2)) << 6)
+ (decode(s.charAt(i + 3)));

os.write((tri >> 16) & 255);
if (s.charAt(i + 2) == '=')
break;
os.write((tri >> 8) & 255);
if (s.charAt(i + 3) == '=')
break;
os.write(tri & 255);

i += 4;
}
}
private static int decode(char c) {
if (c >= 'A' && c <= 'Z')
return ((int) c) - 65;
else if (c >= 'a' && c <= 'z')
return ((int) c) - 97 + 26;
else if (c >= '0' && c <= '9')
return ((int) c) - 48 + 26 + 26;
else
switch (c) {
case '+':
return 62;
case '/':
return 63;
case '=':
return 0;
default:
throw new RuntimeException("unexpected code: " + c);
}
}

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：

String plaintext = "abcd";
String ciphertext = DES.encryptDES(plaintext, "20120401");
System.out.println("明文：" + plaintext);
System.out.println("密钥：" + "20120401");
System.out.println("密文：" + ciphertext);
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：

NSString *plaintext = @"abcd";
NSString *ciphertext = [EncryptUtil encryptUseDES:plaintext key:@"20120401"];
NSLog(@"明文：%@",plaintext);
NSLog(@"秘钥：%@",@"20120401");
NSLog(@"密文：%@",ciphertext);

输出结果：

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

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

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