由于公司需求，需要把获取到的UUID十六进制的字符串，转为byte数组，然后在进行base64加密。

一、UUID的生成

UUID最好通过SSKeyChain存到钥匙串中

//获取uuid
+(NSString *)getDeviceId{
    NSString * currentDeviceUUIDStr = [SSKeyChain passwordForService:UUID account:@"installationId"];
    if (currentDeviceUUIDStr == nil || [currentDeviceUUIDStr isEqualToString:@""]){
        NSUUID * currentDeviceUUID  = [UIDevice currentDevice].identifierForVendor;
        currentDeviceUUIDStr = currentDeviceUUID.UUIDString;
        currentDeviceUUIDStr = [currentDeviceUUIDStr stringByReplacingOccurrencesOfString:@"-" withString:@""];
        currentDeviceUUIDStr = [currentDeviceUUIDStr lowercaseString];
        [SSKeyChain setPassword: [WebHelper stringToByte:currentDeviceUUIDStr] forService:UUID account:@"installationId"];
    }
    NSLog(@"installationId+++++%@",currentDeviceUUIDStr);
    return currentDeviceUUIDStr;
}

二、十六进制的字符串转为byte数组

//从字符串中取字节数组,然后再用base64进行转换
+(NSString*)stringToByte:(NSString*)string {
    NSString *hexString=[[string uppercaseString] stringByReplacingOccurrencesOfString:@" " withString:@""];
    if ([hexString length]%2!=0) {
        return nil;
    }
    Byte bytes[16] = {0};
    int j=0;
    for(int i=0;i<[hexString length];i++) {
        int int_ch;
        unichar hex_char1 = [hexString characterAtIndex:i]; ////两位16进制数中的第一位(高位*16)
        int int_ch1;
        if(hex_char1 >= '0' && hex_char1 <='9')
            int_ch1 = (hex_char1-48)*16;   //// 0 的Ascll - 48
        else if(hex_char1 >= 'A' && hex_char1 <='F')
            int_ch1 = (hex_char1-55)*16; //// A 的Ascll - 65
        else
            return nil;
        i++;

        unichar hex_char2 = [hexString characterAtIndex:i]; ///两位16进制数中的第二位(低位)
        int int_ch2;
        if(hex_char2 >= '0' && hex_char2 <='9')
            int_ch2 = (hex_char2-48); //// 0 的Ascll - 48
        else if(hex_char2 >= 'A' && hex_char2 <='F')
            int_ch2 = hex_char2-55; //// A 的Ascll - 65
        else
            return nil;

        int_ch = int_ch1+int_ch2;  ///将转化后的数放入Byte数组里
        NSLog(@"int_ch=%d",int_ch);
        bytes[j] = int_ch;  ///将转化后的数放入Byte数组里
        j++;

    }
//进行base64加密
    NSData *byteData = [[NSData alloc] initWithBytes:bytes length:16];

    NSData *base64Data = [byteData base64EncodedDataWithOptions:0];

    NSString *baseString = [[NSString alloc]initWithData:base64Data encoding:NSUTF8StringEncoding];

    NSLog(@"++++++++++++base64+++++%@",baseString);
    //base64去除多余的字符

    return [WebHelper takeOutBaseCode:baseString];
}

三、对获取到base64字符串做处理

//base64编码中的+改为-，/改为_,==去掉

+ (NSString *)takeOutBaseCode:(NSString *)baseString {
    // + 号改为-号
    NSString *firstString = [baseString stringByReplacingOccurrencesOfString:@"+" withString:@"-"];
    //  /改为下划线
    NSString *secondString = [firstString stringByReplacingOccurrencesOfString:@"/" withString:@"_"];
    //去掉==
    NSCharacterSet *set = [NSCharacterSet characterSetWithCharactersInString:@"="];
    NSString *trimmedString = [secondString stringByTrimmingCharactersInSet:set];

    NSLog(@"+++移除特殊字符之后%@",trimmedString);
    return trimmedString;
}