You have probably forgotten your ssh key passphrase. But you have a hunch what it might be. The simple way to check it, is to use ssh-keygen with -y argument which read private key file and print public key :

witr@witr-pc:~$ ssh-keygen -y Enter file in which the key is (/home/witr/.ssh/id_rsa): /tmp/my_private_ssh_key Enter passphrase:

If you input the correct passphrase, it will show you the associated public key. Otherwise, it will display

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