Subject: Key exchange failed. the server key was rejected by the client
Date: 2015-10-08 21:51:57
From: Mark Sanchez
Source: key-exchange-failed-server-key-rejected-client
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	We have downloaded the trial Ultimate SFTP .NET component and have tried to connect to an FTP server we maintain following the basic instructions here: http://www.componentpro.com/doc/sftp/Authenticating-to-an-SFTP-server.htm

	Our project was built in VS 2012 with .NET FW 4.5

	The error we get is "Key exchange failed. the server key was rejected by the client", which happens immediatley after calling the "connect" method.

	For a comparison test, we tried connecting  to the same server uisng WinSCP and were immediately successful.

	We have found some differences in our FTP server logs, which I have bolded (Pardon any mistakes, I had to type this manually):

	SFTP:

	Algorithm negotiation complete: Proceeding with key exchange

	Kex: 'diffie-hellman-group-exchange-sha256' Host Key: 'ssh-rsa' C2S : 'aes256-ctr, hmac-md5, none' S2C : 'aes256-ctr, hmac-md5,none'

	DH Key sizes: Server Public '1024', Private '1023', Client Public '1024'

	Closing connection: An existing connection was forcibly closed by the remote host.

	WinSCP:

	Algorithm negotiation complete: Proceeding with key exchange

	Kex: 'diffie-hellman-group-exchange-sha256' Host Key: 'ssh-rsa' C2S : 'aes256-ctr, hmac-sha2-256, none' S2C : 'aes256-ctr, hmac-sha2,none'

	DH Key sizes: Server Public '4096', Private '4095', Client Public '4096'

	Authenticating password for user: xxx

	Do you see anything in the above log output that might be obvious on your end? I have tried usign the "SetEncryptionAlgorithms" method with all supported algos but got the same message, although the values for the "Key sizes" did change.

	TIA

	Mark Sanchez

	SPEC Services, Inc.

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