I've created public and private keys using PuttyGen then the public key was used to encrypt a message. I am now trying to decrypt such message using the private key with the following command:
echo [my encrypted message] | openssl enc -d -base64 -A | openssl rsautl -decrypt -inkey ~/.ssh/private.ppk
but I get the error:
unable to load Private Key
6870300:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:707:Expecting: ANY PRIVATE KEY
The private key looks like this (actual key omitted):
PuTTY-User-Key-File-2: ssh-rsa
Encryption: none
Comment: rsa-key-20170724
Public-Lines: 6
[...]
Private-Lines: 14
[...]
Private-MAC: [...]
What's wrong?