Deleted authorized_keys from EC2 but still have PPK file and I’m connected

I am not sure about how to get ssh-keygen to create a key using a specific encyprption algorithm.

You could generate your key using OpenSSL directly.

# create 1024 bit rsa and encrypt with des3 
#    make sure you set your umask or chmod this so that it is 0600, 
#    or else ssh will refuse to use it.
openssl genrsa -des3 -out .ssh/id_rsa 1024
# export an ssh public key
ssh-keygen -y -f .ssh/id_rsa > .ssh/id_rsa.pub

You could also convert the cipher of an existing key after the fact using OpenSSL.

openssl rsa -in id_rsa -out newkey_id_rsa -des3

See: genrsa(1), rsa(1), and ssh-keygen(1) for a list of the various options.

According this issue report on the CentOS web site, this is caused by an upstream "feature" in SELinux; if SELinux is enforcing, it will prevent the server from using pubkey authentication. There is no indication that this behavior will change in the near future. To see if this problem applies to you, type sestatus and see if it reports "Current mode" as enforcing.

I know of two workarounds.

• You can set SELinux to permissive mode. Type setenforce 0 to change the policy immediately, and then open /etc/selinux/config and make sure SELINUX=permissive.

• Restore the file to the correct security context:

  restorecon -R -v ~$USER/.ssh