Yubico Forum

The JEDEC JESD 218A endurance specification for flash memory states that if flash power off storage temperature is at 25 degrees C then data retention is 101 weeks (2 years). This is one of the reasons why unpowered flash memory isn't usually a good long-term data storage medium.

I assume that Yubikeys are using flash internally to store the key's state.

So my question is, if I make a backup Yubikey and store it in a safe place just in case I'll need it someday, if that "some day" is several years down the road, will it still work?

Ink on a piece of paper has be known to last for millenia, that could be an alternative

You can note down or print the CSV file.

I understand that I can store the configuration on other media.

Flash unpowered data retention time is a function of the flash temperature when the data was written and the unpowered storage temperature. It's also a function of whether the device is designed for Enterprise use or not. The JEDEC JESD 218A endurance specification for flash memory has a tables on page 24. A lot of these things can make the data retention times vary by more than a factor of two.

I am concerned about needing a backup key quickly in an emergency at a remote location and finding the backup key is dead. In a non-emergency, configuring a new key at HQ to mimic an old one in the field isn't a problem, just an inconvenience. This isn't a criticism of Yubikey, as any security key will have similar issues because they all are going to use flash if they are reconfigurable. I'm just trying to work out procedures to put in place now in order to not get caught out down the road.

This question really got me to thinking as I DO assume that my "backup" Yubikey -- locked away and generally unused in a safe -- WILL function if ever needed.

If this is a potential "problem" ... would periodically using the "backup" key serve keep it sufficiently charged/refreshed?

I too would like a definitive answer to this post as well.
I have a backup Yubikey stored away in case it is ever needed.

How long before it may loose data.

Cheers!

The stated NVM retention is 25 years at +25 degrees C, so I believe this should not be a reason to consider a backup key