Key authent doesn't work with open ssh 6.6

[iuga2000]

I use AndFtp to connect on my synology NAS with RSA key. Synology updated recently openssh to V6.6 in last firmware (DSM 5.1). Since this upgrade, I can't connect with AndFtp , I have a message "algorithm negotiation failed" on scp protocol. It works with sftp but not with scp. I tried to regenerate a new key pair and use it, but I have the same message.

Others clients like connectbot continues to work.

Thank you for your help

[support]

Some feedback from another user about possible cause:

Just wanted to pass along an issue I encountered this morning. The
latest update to openssh on one of my Debian hosts made AndFTP unable
to connect via ssh/scp. Long story made short, the KEX algorithm
AndFTP uses appears to be no longer supported by the default openssh
config. Going back and adding diffie-hellman-group-exchange-sha1 to
the list of allowed algos got things working again. I imagine some
users won't have the ability to modify their servers, though. The new
list of default-supported algos is:
curve25519-sha256@libssh.org,
ecdh-sha2-nistp256,
ecdh-sha2-nistp384,
ecdh-sha2-nistp521,
diffie-hellman-group-exchange-sha256,
diffie-hellman-group14-sha1

[iuga2000]

Thank you for this information
I can modify my server config.
Do you know the name of the config file to change to add the right algorithm ?

[support]

AndFTP 4.2 adds support for DH-SHA256 so there is not need to modify your SSH server configuration anymore.