Keysafe securely backs up a gpg secret key or other short secret to the cloud. But not yet. Today's alpha release only supports storing the data locally, and I still need to finish tuning the argon2 hash difficulties with modern hardware. Other than that, I'm fairly happy with how it's turned out.
Keysafe is written in Haskell, and many of the data types in it keep track of the estimated CPU time needed to create, decrypt, and brute-force them. Running that through a AWS SPOT pricing cost model lets keysafe estimate how much an attacker would need to spend to crack your password.
(Above is for the password "makesad spindle stick")
If you'd like to be an early adopter, install it like this:
sudo apt-get install haskell-stack libreadline-dev libargon2-0-dev zenity stack install keysafe
~/.local/bin/keysafe --backup --store-local to back up a gpg key
I still need to tune the argon2 hash difficulty, and I need benchmark data to do so. If you have a top of the line laptop or server class machine that's less than a year old, send me a benchmark:
~/.local/bin/keysafe --benchmark | mail email@example.com -s benchmark
Bonus announcement: http://hackage.haskell.org/package/zxcvbn-c/ is my quick Haskell interface to the C version of the zxcvbn password strength estimation library.
PS: Past 50% of my goal on Patreon!