Hello,
Did all the step by step until the command:
node main.js
I can see the public key
open a new terminal
Now connect the USB Core in raspberry and put the core in DFU mode flashing yellow color
cd core_keys
spark keys save INPUT_CORE_ID_HERE
but I receive this error message:
Apparently I didn’t find a DFU divice? util said dfu-util 0.5
dfu-util does currently only support DFU version 1.0
where is the problem?
Sounds like you might be on Ubuntu?
Your DFU-util version is too long. Can you try on some other machine instead to save the keys? 
I don’t have other machine, have another way to solve this problem?
You can try to upgrade DFU-util then?
Or might be related to this:
I change the dfu-util version to 0.8 and don’t work yet.
1.) What OS are you on?
2.) How did you install the DFU-util driver?
3.) Is the core in DFU-mode (blinking yellow)?
raspberry raspian
STEPS TO INSTALL DFU
wget http://dfu-util.sourceforge.net/releases/dfu-util-0.8.tar.gz
tar -zxvf dfu-util-0.8.tar.gz dfu-util-0.8
cd dfu-util-0.8/
./autogen.sh
./configure
make
sudo make install
My core is blinking yellow
Libusb 1.0 installed
What does dfu-util -V say?
Try sudo dfu-util -l
dfu-util 0.8
I found part of solution , now dfu-util -l show
but if I insert:
spark keys save MYcodeid
receive message dfu-util cant find core
try sudo spark keys save core_id
You need to replace core_id with id if you know what it is… or you can use some temporary name but not recommended since the file needs to be named with the core_id to work with the local 
ok I made it insert the correct core id but receive error message, can’t find core
Use this command instead: sudo dfu-util -d 1d50:607f -a 1 -s 0x00002000: 612 -U core_id.der
and
openssl rsa -in core_id.der -inform DER -outform PEM -pubout -out core_id.pub.pem
the 2 command works, but what they make?
It is the same as spark keys save core_id but i don’t want to waste time figuring out what’s wrong with your setup.
Basically,
1.) grab the core private key from the external flash
2.) Convert to a public key using openssl.
3.) Done!
So now my spark core is in my local cloud?
You probably need to play around with the default core + 
setup first and have a better understanding of how everything comes together!
This might also be useful for you find out what’s wrong:
thank you,
I made this tutorial is all working, Now I need test if your 2 commands turn my core into local cloud.
You need to copy the file to the core_keys directory basically… and test…
I have more questions,
where can I find local token,
and what is the format of string $url = “https://api.spark.io/v1/devices/$deviceID/led/?access_token=$dispositivo”; to local cloud?