Using SSH public key to encrypt a file or string

encrypt.txt

# Recently I had to send a password to someone over Skype. Since that's obviously not a good idea, I asked for 
# the person's public SSH RSA key, and used it to encrypt the password itself.


# Convert the public key into PEM format
ssh-keygen -f path/to/id_rsa.pub -e -m pem > ~/id_rsa.pub.pem

# Using the public pem file to encrypt a string
echo "sometext" | openssl rsautl -encrypt -pubin -inkey ~/id_rsa.pub.pem > ~/encrypted.txt

# Or a file
cat ~/some_file.txt | openssl rsautl -encrypt -pubin -inkey ~/id_rsa.pub.pem > ~/encrypted.txt

# To decrypt, you'll need the private key
cat ~/encrypted.txt | openssl rsautl -decrypt -inkey path/to/id_rsa > ~/decrypted.txt

Thank you for this!
I made a bash script to put this all together and easily encrypt/decrypt files with ssh key: https://github.com/S2-/sshencdec

@phrfpeixoto

I tried doing the above steps but i was unable to load the public key to encrypt.

i tried finding solution on stack overflow but couldn't do much help.
here is the snap.
i also tried changing the encoding to different encodings and tried all possible encodings.
but it didn't load.
please help

@phrfpeixoto

I tried doing the above steps but i was unable to load the public key to encrypt.

i tried finding solution on stack overflow but couldn't do much help.
here is the snap.
i also tried changing the encoding to different encodings and tried all possible encodings.
but it didn't load.
please help

Did your private key is OPENSSH instead of RSA? if yes, the above command will not work. I'm still finding other method instead of convert it to RSA using putty

@phrfpeixoto

I tried doing the above steps but i was unable to load the public key to encrypt.

i tried finding solution on stack overflow but couldn't do much help.
here is the snap.
i also tried changing the encoding to different encodings and tried all possible encodings.
but it didn't load.
please help

I'm very sorry I missed this. It's almost 1y old. Let me know if you still need help.

@phrfpeixoto
I tried doing the above steps but i was unable to load the public key to encrypt.
i tried finding solution on stack overflow but couldn't do much help.
here is the snap.
i also tried changing the encoding to different encodings and tried all possible encodings.
but it didn't load.
please help

Did your private key is OPENSSH instead of RSA? if yes, the above command will not work. I'm still finding other method instead of convert it to RSA using putty

My keys are RSA. Works without issues.

I've just tried this with fresh keys generated with ssh-keygen and when trying to encrypt the string I get a unable to load public key error.

I've just tried this with fresh keys generated with ssh-keygen and when trying to encrypt the string I get a unable to load public key error.

Me too. it doens't work

Can you please share the error message you got?

I got "unable to load the public key" at step "Using the public pem file to encrypt a string"
even tho the id_rsa.pub.pem file got created

Are you sure you are using RSA keys? How did you generate those?

I executed
ssh-keygen -f path/to/id_rsa.pub -e -m pem > ~/id_rsa.pub.pem
with id_rsa.pub having been generated with
ssh-keygen -t rsa -b 4096 -C "[email protected]"

Okay, for anyone facing unable to load public key error:

• Open your private key by text editor (vi, nano, etc..., vi ~/.ssh/id_rsa) and confirm your key is in OPENSSH key format
• Convert OpenSSH back to PEM (Command below will OVERWRITE original key). This command will ask you enter old password to decrypt old key and new password to encrypt new PEM key

ssh-keygen -p -m PEM -f ~/.ssh/id_rsa

then you can execute OP commands.

If you want to create new key in PEM format, execute below commands:

ssh-keygen -m PEM -t rsa -b 4096 -C "[email protected]"

use this to convert your existing key to pem

ssh-keygen -f ~/.ssh/id_rsa.pub -e -m PKCS8 > id_rsa.pem.pub

and all works

use this to convert your existing key to pem

ssh-keygen -f ~/.ssh/id_rsa.pub -e -m PKCS8 > id_rsa.pem.pub

and all works

This worked for me.