//用法 加密转base 64

NSString *str = [self base64StringFromText:@"qingjoin" withKey:@"key"];

//转base 64 解密

 NSString *stred = [self textFromBase64String:str withKey:@"key"];

//文本先进行DES加密。然后再转成base64

+ (NSString *)base64StringFromText:(NSString *)text withKey:(NSString*)key

{

    if (text && ![text isEqualToString:@""]) {

        //取项目的bundleIdentifier作为KEY

        //NSString *key = [[NSBundle mainBundle] bundleIdentifier];

        NSData *data = [text dataUsingEncoding:NSUTF8StringEncoding];

        //IOS 自带DES加密 Begin

        data = [self DESEncrypt:data WithKey:key];

        //IOS 自带DES加密 End

        return [self base64EncodedStringFrom:data];

    }

    else {

        return @"";

    }

}

//先把base64转为文本。然后再DES解密

+ (NSString *)textFromBase64String:(NSString *)base64 withKey:(NSString*)key

{

    if (base64 && ![base64 isEqualToString:@""]) {

        //取项目的bundleIdentifier作为KEY

        //NSString *key = [[NSBundle mainBundle] bundleIdentifier];

        NSData *data = [self dataWithBase64EncodedString:base64];

        //IOS 自带DES解密 Begin

        data = [self DESDecrypt:data WithKey:key];

        //IOS 自带DES加密 End

        return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

    }

    else {

        return @"";

    }

}

/******************************************************************************

 函数名称 : + (NSData *)DESEncrypt:(NSData *)data WithKey:(NSString *)key

 函数描述 : 文本数据进行DES加密

 输入参数 : (NSData *)data

 (NSString *)key

 输出参数 : N/A

 返回参数 : (NSData *)

 备注信息 : 此函数不可用于过长文本

 ******************************************************************************/

+ (NSData *)DESEncrypt:(NSData *)data WithKey:(NSString *)key

{

    char keyPtr[kCCKeySizeAES256+];

    bzero(keyPtr, sizeof(keyPtr));

    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [data length];

    size_t bufferSize = dataLength + kCCBlockSizeAES128;

    void *buffer = malloc(bufferSize);

    size_t numBytesEncrypted = ;

    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmDES,

                                          kCCOptionPKCS7Padding | kCCOptionECBMode,

                                          keyPtr, kCCBlockSizeDES,

                                          NULL,

                                          [data bytes], dataLength,

                                          buffer, bufferSize,

                                          &numBytesEncrypted);

    if (cryptStatus == kCCSuccess) {

        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];

    }

    free(buffer);

    return nil;

}

/******************************************************************************

 函数名称 : + (NSData *)DESEncrypt:(NSData *)data WithKey:(NSString *)key

 函数描述 : 文本数据进行DES解密

 输入参数 : (NSData *)data

 (NSString *)key

 输出参数 : N/A

 返回参数 : (NSData *)

 备注信息 : 此函数不可用于过长文本

 ******************************************************************************/

+ (NSData *)DESDecrypt:(NSData *)data WithKey:(NSString *)key

{

    char keyPtr[kCCKeySizeAES256+];

    bzero(keyPtr, sizeof(keyPtr));

    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [data length];

    size_t bufferSize = dataLength + kCCBlockSizeAES128;

    void *buffer = malloc(bufferSize);

    size_t numBytesDecrypted = ;

    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmDES,

                                          kCCOptionPKCS7Padding | kCCOptionECBMode,

                                          keyPtr, kCCBlockSizeDES,

                                          NULL,

                                          [data bytes], dataLength,

                                          buffer, bufferSize,

                                          &numBytesDecrypted);

    if (cryptStatus == kCCSuccess) {

        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];

    }

    free(buffer);

    return nil;

}

/******************************************************************************

 函数名称 : + (NSData *)dataWithBase64EncodedString:(NSString *)string

 函数描述 : base64格式字符串转换为文本数据

 输入参数 : (NSString *)string

 输出参数 : N/A

 返回参数 : (NSData *)

 备注信息 :

 ******************************************************************************/

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

+ (NSData *)dataWithBase64EncodedString:(NSString *)string

{

    if (string == nil)

        [NSException raise:NSInvalidArgumentException format:nil];

    if ([string length] == )

        return [NSData data];

    static char *decodingTable = NULL;

    if (decodingTable == NULL)

    {

        decodingTable = malloc();

        if (decodingTable == NULL)

            return nil;

        memset(decodingTable, CHAR_MAX, );

        NSUInteger i;

        for (i = ; i < ; i++)

            decodingTable[(short)encodingTable[i]] = i;

    }

    const char *characters = [string cStringUsingEncoding:NSASCIIStringEncoding];

    if (characters == NULL)     //  Not an ASCII string!

        return nil;

    char *bytes = malloc((([string length] + ) / ) * );

    if (bytes == NULL)

        return nil;

    NSUInteger length = ;

    NSUInteger i = ;

    while (YES)

    {

        char buffer[];

        short bufferLength;

        for (bufferLength = ; bufferLength < ; i++)

        {

            if (characters[i] == '\0')

                break;

            if (isspace(characters[i]) || characters[i] == '=')

                continue;

            buffer[bufferLength] = decodingTable[(short)characters[i]];

            if (buffer[bufferLength++] == CHAR_MAX)      //  Illegal character!

            {

                free(bytes);

                return nil;

            }

        }

        if (bufferLength == )

            break;

        if (bufferLength == )      //  At least two characters are needed to produce one byte!

        {

            free(bytes);

            return nil;

        }

        //  Decode the characters in the buffer to bytes.

        bytes[length++] = (buffer[] << ) | (buffer[] >> );

        if (bufferLength > )

            bytes[length++] = (buffer[] << ) | (buffer[] >> );

        if (bufferLength > )

            bytes[length++] = (buffer[] << ) | buffer[];

    }

    bytes = realloc(bytes, length);

    return [NSData dataWithBytesNoCopy:bytes length:length];

}

/******************************************************************************

 函数名称 : + (NSString *)base64EncodedStringFrom:(NSData *)data

 函数描述 : 文本数据转换为base64格式字符串

 输入参数 : (NSData *)data

 输出参数 : N/A

 返回参数 : (NSString *)

 备注信息 :

 ******************************************************************************/

+ (NSString *)base64EncodedStringFrom:(NSData *)data

{

    if ([data length] == )

        return @"";

    char *characters = malloc((([data length] + ) / ) * );

    if (characters == NULL)

        return nil;

    NSUInteger length = ;

    NSUInteger i = ;

    while (i < [data length])

    {

        char buffer[] = {,,};

        short bufferLength = ;

        while (bufferLength <  && i < [data length])

            buffer[bufferLength++] = ((char *)[data bytes])[i++];

        //  Encode the bytes in the buffer to four characters, including padding "=" characters if necessary.

        characters[length++] = encodingTable[(buffer[] & 0xFC) >> ];

        characters[length++] = encodingTable[((buffer[] & 0x03) << ) | ((buffer[] & 0xF0) >> )];

        if (bufferLength > )

            characters[length++] = encodingTable[((buffer[] & 0x0F) << ) | ((buffer[] & 0xC0) >> )];

        else characters[length++] = '=';

        if (bufferLength > )

            characters[length++] = encodingTable[buffer[] & 0x3F];

        else characters[length++] = '=';

    }

    return [[NSString alloc] initWithBytesNoCopy:characters length:length encoding:NSASCIIStringEncoding freeWhenDone:YES];

}