How to encrypt and decrypt a string with ssh key pair?

Question

SSH

What would the commands for encrypting and decrypting a string with an SSH key pair look like? Interested in exactly how to apply openssl to the input string.

Answer 1

Create a key in PEM format (or convert the current public key to PEM format)
We send the public key to a friend who encrypts the message.txt file with it:
Sends EncryptedMessage.txt to you, and you decrypt it with your private key:

openssl rsautl -decrypt -inkey id_rsa -in EncryptedMessage.txt -out DecryptedMessage.txt

Answer 2

superuser.com/questions/576506/how-to-use-ssh-rsa-...
Isn't it?