Encryption keys
Backing up data is usually a good thing e.g. in case you lose your files. But backing up encryption keys is different. There is a balance to be found between keeping the keyfile in as few places as possible and keeping copies of it. Go too far one way, and you might be unable to access your encrypted files. Go too far the other way, and the encryption key could be compromised. The OpenPGP smart card can store your encryption keys in a secure manner and it works with the GnuPG cryptographic software suite.