How Yubikey works with GPG?

Question

please help me to understand how yubikey works with GPG.

I have a key, and i moved it to yubikey. But before that i made a backup my .gnupg folder.

After that, i removed yubikey to use it on another PC.

On the PC i removed .gnupg folder and restored .gnupg folder and restored .gnupg folder from backup.

So, i expect that i have the same keys on my PC and on yubikey.

But if i encrypt something with yubikey, like gpg -e -r 'mykey' 123.txt

I can't decrypt it on my PC with the same key.

It says:

gpg: encrypted with RSA key, ID 3435KSLDKJFLKSJF234
gpg: decryption failed: No secret key"

But i have secret key. What happens?

Answer 1

Yubikey stores the private keys and thus the operations executed on Yubikey are sign and decrypt. (The public keys can also be found on the Yubikey card - because each OpenPGP private key contains a copy of the public key)

When you move a key to Yubikey - the private key is removed (actually only a stub remains) from GnuPG keys folder and it resides only on the Yubikey card. The only way to decrypt now is by using the Yubikey card.