FileZilla public key not working (Successfully loaded 0 key pairs from file)

Question

I currently have troubles logging in with a public key using FileZilla. Neither the root user, not an other user accept the key.

Now the strange thing is when using putty it is working without any troubles.

I do not have the slightest idea what the problem might be.

Things I checked:

• Connection to the server:
  The server does receive the authentication attempt
• The key is located in ~/.ssh/authorized_keys
• The file permissions are correct (700 for ~/.ssh and 600 for ~/.ssh/authorized_keys)
• Using the same key with PuTTY. This is working!
• Password login over SFTP is working as well
• Trying a new key: Not working as well (PuTTY is accepting it without problems)

Logs:

PuTTY:

Event Log: Writing new session log (SSH packets mode) to file: PuTTY.log
Event Log: Looking up host "x.x.x.x"
Event Log: Connecting to x.x.x.x port 22
Event Log: Server version: SSH-2.0-OpenSSH_6.0p1 Debian-4+deb7u2
Event Log: Using SSH protocol version 2
Event Log: We claim version: SSH-2.0-PuTTY_Release_0.63_(file_config_0.6.1)
Event Log: Doing Diffie-Hellman group exchange
Event Log: Doing Diffie-Hellman key exchange with hash SHA-256
Event Log: Host key fingerprint is:
Event Log: ssh-rsa 2048 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
Event Log: Initialised AES-256 SDCTR client->server encryption
Event Log: Initialised HMAC-SHA-256 client->server MAC algorithm
Event Log: Initialised AES-256 SDCTR server->client encryption
Event Log: Initialised HMAC-SHA-256 server->client MAC algorithm
Event Log: Reading private key file "C:\Program Files (x86)\Putty\PBS - Verknüpfungen\root.key.ppk"
Event Log: Offered public key
Event Log: Offer of public key accepted
Event Log: Sent public key signature
Event Log: Access granted
Event Log: Opening session as main channel
Event Log: Opened main channel
Event Log: Requesting X11 forwarding
Event Log: X11 forwarding enabled
Event Log: Allocated pty (ospeed 38400bps, ispeed 38400bps)
Event Log: Started a shell/command

FileZilla:

Status: Connecting to x.x.x.x...
Response:   fzSftp started, protocol_version=2
Command:    keyfile "C:\Program Files (x86)\Putty\PBS - Verknüpfungen\root.key.ppk"
Command:    open "[email protected]" 22
Trace:  Looking up host "x.x.x.x"
Trace:  Connecting to x.x.x.x port 22
Trace:  We claim version: SSH-2.0-PuTTY_Local:_Mar_29_2015_12:25:15
Trace:  Server version: SSH-2.0-OpenSSH_6.0p1 Debian-4+deb7u2
Trace:  We believe remote version has SSH-2 channel request bug
Trace:  Using SSH protocol version 2
Trace:  Doing ECDH key exchange with hash SHA-256
Trace:  Host key fingerprint is:
Trace:  ecdsa-sha2-nistp256 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
Trace:  Initialised AES-256 SDCTR client->server encryption
Trace:  Initialised HMAC-SHA-256 client->server MAC algorithm
Trace:  Initialised AES-256 SDCTR server->client encryption
Trace:  Initialised HMAC-SHA-256 server->client MAC algorithm
Trace:  Successfully loaded 0 key pairs from file
Error:  Connection attempt interrupted by user

(The last message is caused by me pressing cancel after being asked for the password)

Answer 1

It's probably the umlaut in the path. The interface between FileZilla and the internal psftp process is not Unicode-enabled.

When I tried a path with diacritics, psftp didn't load the key either:

Trace:  Successfully loaded 0 key pairs from file

When I removed the diacritics, it worked:

Trace:  Successfully loaded 1 key pair from file
Trace:  Offered public key from "C:\path\key.ppk"