In Debian 7 it seems like ssh doesn't accept ed25519 keys.support for ECDSA was not added until end of 2013, but wheezy is olderHow do I enable this in Debian 7? 
Enable ed25519 in Debian wheezy
debian;ssh;encryption
There are updated openssh client and server packages in Wheezy Backports.According to the changelog, the backported version can work with ED25519 keys:openssh (1:6.6p1-4~bpo70+1) wheezy-backports; urgency=lowRebuild for wheezy-backports.-- Colin Watson   Wed, 30 Apr 2014 09:59:29  +0100[...]openssh (1:6.5p1-1) unstable; urgency=medium[...]Generate ED25519 host keys on fresh installations.  Upgraders who  wish  to add such host keys should manually add 'HostKey  /etc/ssh/ssh_host_ed25519_key' to /etc/ssh/sshd_config and run  'ssh-keygen -q -f /etc/ssh/ssh_host_ed25519_key -N  -t ed25519'.-- Colin Watson   Mon, 10 Feb 2014 14:58:26  +0000To install wheezy-backports packages, follow the instructions.  In short, you need to add the following line to your /etc/apt/sources.list:deb http://http.debian.net/debian wheezy-backports mainIt would be wise to carefully read the backports site before making use of the repo.