file encrytion and decryption in VB .NET

I think that the key used for encryption is going to be a problem. Please see the answer from Eric Lippert at asymetric-cryptography-example-in-c-sharp for reasons. You don't want the key to be hard-coded into the program. If the data transfer needs to comply with FIPS 140-2, you might want to have a look at http://csrc.nist.gov/publications/fips/fips140-2/fips1402annexa.pdf.

I do not know if simply transmitting the file using SSL will be sufficient - you can research that - but if so then that would make your program much easier to write. You might want to set the client-permission on the SFTP (or whatever) server to only allow writing.

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Andrew