md5

- (NSString *)md5 {
    const char *cStr = [self UTF8String];
    unsigned char result[16] = {0};
    CC_MD5(cStr, strlen(cStr), result);
    return [NSString stringWithFormat:
            @"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
            result[0], result[1], result[2], result[3],
            result[4], result[5], result[6], result[7],
            result[8], result[9], result[10], result[11],
            result[12], result[13], result[14], result[15]
            ];
}