From wiliGear wiki

Dropbear Public Key Authentication

Abstract

SSH, or secure shell, is a protocol that allows remote logins to a machine. It uses encrypted connections and can use public key authentication instead of plain passwords.

Public key authentication can use DSS and RSA keys and works with keys generated by the popular OpenSSH package. Putting your public key from OpenSSH into the file .ssh/authorized_keys should be enough to let you login from the machine where you keep the corresponding private key. Please note that the permissions on the .ssh directory must not include group or other write permission, otherwise dropbear will refuse public key authentication.

Configuration examples

Generate key pair

Using OpenSSH client on Linux create the public and private key pair:

ssh-keygen -t dsa

Next copy the public key with '~/.ssh/id_dsa.pub' to '/tmp' on wili-box device using sftp or scp. If wili-box has scp enabled:

scp ~/.ssh/id_dsa.pub admin@192.168.2.66:/tmp

You can also copy & paste the public key into wili-box. The public key is in text.

Create authorized_keys

On wili-box device create '.ssh' folder in '/etc/persistent':

mkdir /etc/persistent/.ssh
chmod 0700 /etc/persistent/.ssh

Add the public key to the authorized_keys file on wili-box:

cat /tmp/id_*.pub >> /etc/persistent/.ssh/authorized_keys
chmod 0600 /etc/persistent/.ssh/authorized_keys

Connecting to wili-box with Public Key

If everything configured right, ssh will not ask for a password:

ssh admin@192.168.2.66

Known limitations

Dropbear cannot use private keys in OpenSSH format. You can use the dropbearconvert program to convert an OpenSSH format key for use by dbclient or you can use dropbearkey to create a new key.