I'm trying to find a way to decrypt an encrypted file on a 'virgin' EC2-instance. These EC-instances I use (Ubuntu Lucid) only hold my AWS-created public ssh-key. If can use this to decrypt a file, I can feed it encrypted files (for example a bash-script holding a password to my subversion-repository).
So, my question, can I use my ssh-key to encrypt/decrypt a file?
The file:
echo 'This is a sekret' >/tmp/msg.txt
Export public key (in case you don't have it/lose it):
openssl rsa -in ~/private.pem -out /tmp/public.pub -outform PEM -pubout
Encrypt file with public key (anyone can have this key):
openssl rsautl -encrypt -inkey /tmp/public.pub -pubin -in /tmp/msg.txt -out /tmp/file.enc
Decrypt the file with private key (only you should have the private key):
openssl rsautl -decrypt -inkey ~/private.pem -in /tmp/file.enc -out /tmp/decrypted.txt
The decoded message:
cat /tmp/decrypted.txt
You can use a public key to encrypt a file but you will need the corresponding private key to decrypt it. So, yes, you should be able to use your ssh-key to encrypt/decrypt a file, as long as you have access to both the public and private key.
If you just want to encrypt/decrypt using your ssh keys, ssh-vault could be useful, more info here: http://ssh-vault.com/about/
