DES加密算法

一、DES加密算法介绍

• 要求秘钥必须是8个字节，即64bit长度
• 因为秘钥是byte[8]，代表字符串也可以是非可见的字节，可以与Base64编码算法一起使用
• 加密、解密都需要通过字节数组作为数据和密钥进行处理

二、对称加密
DES 加密算法属于对称加密。
即利用制定的密钥，按照密码的长度截取数据，分成数据块，和密钥进行复杂的移位、算数运算或者数据处理等操作，形成只有特定的密码才能够解开的数据。加密与解密用的是同一个密钥

三、代码
1.使用DES加密，示例代码

//加密
+(NSString *) encryptUseDES2:(NSString *)plainText key:(NSString *)key{
    NSString *ciphertext = nil;
    const char *textBytes = [plainText UTF8String];
    size_t dataLength = [plainText length];
    //==================
    
    uint8_t *bufferPtr = NULL;
    size_t bufferPtrSize = 0;
    size_t movedBytes = 0;
    
    bufferPtrSize = (dataLength + kCCBlockSizeDES) & ~(kCCBlockSizeDES - 1);
    bufferPtr = malloc( bufferPtrSize * sizeof(uint8_t));
    memset((void *)bufferPtr, 0x0, bufferPtrSize);
    
    
    NSString *testString = key;
    NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];
    Byte *iv = (Byte *)[testData bytes];
    
    
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmDES,
                                          kCCOptionPKCS7Padding,
                                          [key UTF8String], kCCKeySizeDES,
                                          iv,
                                          textBytes, dataLength,
                                          (void *)bufferPtr, bufferPtrSize,
                                          &movedBytes);
    if (cryptStatus == kCCSuccess) {
        
        ciphertext= [XuDes parseByte2HexString:bufferPtr :(int)movedBytes];

    }
    ciphertext=[ciphertext uppercaseString];//字符变大写
    
    return ciphertext ;
}

2.使用DES进行解密计算

//解密
+(NSString *)decryptUseDES:(NSString *)cipherText key:(NSString *)key
{
    
    NSData* cipherData = [XuDes convertHexStrToData:[cipherText lowercaseString]];
    NSLog(@"++++++++///%@",cipherData);
    unsigned char buffer[1024];
    memset(buffer, 0, sizeof(char));
    size_t numBytesDecrypted = 0;
    NSString *testString = key;
    NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];
    Byte *iv = (Byte *)[testData bytes];
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmDES,
                                          kCCOptionPKCS7Padding,
                                          [key UTF8String],
                                          kCCKeySizeDES,
                                          iv,
                                          [cipherData bytes],
                                          [cipherData length],
                                          buffer,
                                          1024,
                                          &numBytesDecrypted);
    NSString* plainText = nil;
    if (cryptStatus == kCCSuccess) {
        NSData* data = [NSData dataWithBytes:buffer length:(NSUInteger)numBytesDecrypted];
        plainText = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    }
    return plainText;

}

加密解密中有两个方法调用，其实是为了16进制与data之间的转换。有些宝宝们的公司并未转换成16进制，而是需要跟base64共同加解密、方法使用，只需要将得出的plainText的值转换成base64即可。

加密时转成16进制

+(NSString *) parseByte2HexString:(Byte *) bytes  :(int)len{
    
    
    NSString *hexStr = @"";
    
    if(bytes)
    {
        for(int i=0;i

解密时转回data

+ (NSData *)convertHexStrToData:(NSString *)str {
    if (!str || [str length] == 0) {
        return nil;
    }
    
    NSMutableData *hexData = [[NSMutableData alloc] initWithCapacity:8];
    NSRange range;
    if ([str length] % 2 == 0) {
        range = NSMakeRange(0, 2);
    } else {
        range = NSMakeRange(0, 1);
    }
    for (NSInteger i = range.location; i < [str length]; i += 2) {
        unsigned int anInt;
        NSString *hexCharStr = [str substringWithRange:range];
        NSScanner *scanner = [[NSScanner alloc] initWithString:hexCharStr];
        
        [scanner scanHexInt:&anInt];
        NSData *entity = [[NSData alloc] initWithBytes:&anInt length:1];
        [hexData appendData:entity];
        
        range.location += range.length;
        range.length = 2;
    }
    
    NSLog(@"hexdata: %@", hexData);
    return hexData;
}