Create an SSH2 private key on the client machine, if one doesn't already exist, and install it by appending a line to ~/.ssh2/identification:

$ mkdir -p ~/.ssh2                                       If it doesn't already exist
$ chmod 700 ~/.ssh2
$ cd ~/.ssh2
$ ssh-keygen2                                            Creates id_dsa_1024_a
$ echo "IdKey id_dsa_1024_a" >> identification     (Appending)

Copy its public key to the OpenSSH server machine:

$ scp2 id_dsa_1024_a.pub remoteuser@remotehost:.ssh/

Log into the OpenSSH server host and use OpenSSH's ssh-keygen to import the public key, creating an OpenSSH format key: [Recipe 6.6]

$ ssh2 -l remoteuser remotehost
Password: ********

remotehost$ cd ~/.ssh
remotehost$ ssh-keygen -i > imported-ssh2-key.pub
Enter file in which the key is (/home/smith/.ssh/id_rsa): id_dsa_1024_a.pub

Install the new public key by appending a line to ~/.ssh/authorized_keys:

remotehost$ cat imported-ssh2-key.pub >> authorized_keys   (Appending)

Log out and log back in using the new key:

remotehost$ exit
$ ssh2 -l remoteuser remotehost