We use the ftp2 library moving files to from a secure server. Due to a pci scan we had to turn off 3des ciphers and customers started calling. Put them back in and they were fine. Our dll is dated march 2014. Is there a way to force ftp2 to a higher cipher ?
Your first step should be to upgrade to the current release (your current unlock code will work with it). http://www.chilkatsoft.com/downloads.asp
Download .net components or .net core ? I am guessing .net components.
With SSL/TLS, it is the server that chooses the cipher suite. The client tells the server which cipher suites it implements, and then the server, if one is acceptable, makes the choice. If all of your servers would never choose 3DES, then really there's nothing you need to do.
You could, however, set the SslAllowedCiphers property = "best-practices". See the online reference documentation. This would prevent RC4, DES, or 3DES from ever being used.
(You would not choose ".NET Core". If you were using .NET Core, then you would know it.)