client device ID

[DanBarclay]

Find out the ID of the device on which the client is running?
Situation :
When the client is working with the application, he left the program for a short time and must re-enter the username and password when re-logging in. 
The idea: 
To remember the ID of the device on which the client is working and, if the device ID has not changed when re-logging in, restore authorization without a LOGIN-PASSWORD request

Question: How do I find out the ID of the device on which the client is running?

Almost impossible to ID a physical machine.   I've needed to do that in the past and used cookies.   

ID the "machine" by laying down a unique cookie, then you can check for that ID cookie in the future.  If you need to tie it to a physical machine, create an authorization process to run on that machine to create the cookie initially, then don't allow update/change.   Obviously you'll need to encrypt the cookie contents, but it will work.  SORT OF work.  The problem is that each browser on a machine has its own "cookie space', so there is a "machine" per browser.

Oh, and it is a cookie.  So can be fragile if cookies get nuked.   Not foolproof, but useful.

Dan