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Guaranteed Transmission Protocols For Windows?
Michael writes "Part of our business at my work involves transferring mission critical files across a 2 mbit microwave connection, into a government-run telecommunications center with a very dodgy internal network and then finally to our own server inside the center. The computers at both ends run Windows. What sort of protocols or tools are available to me that will guarantee to get the data transferred across better than a straight Windows file system copy? Since before I started working here, they've been using FTP to upload the files, but many times the copied files are a few kilobytes smaller than the originals."
Using modern encryption like SSH does guarantee that things *have to add up* since keeping what you start with a secret
When you first wrote this it went against what (little) I knew about encryption. I'm very weak on the math, but I know that some encryption algorithms use a rotor model, meaning that they're just a software implementation of the rotor encryption machines used during WW II (Enigma being the most famous.) So it just doesn't make sense that a transmission error would screw up the process.
I still can't say that no encryption algorithm will choke if there's a transmission error, but I now know for a fact that 3DES (the encryption SSH uses by default) won't. And yes, 3DES is a rotor algorithm.
I decided to get my hands dirty with the DES software on Linux. (3DES is just DES with bigger keys.) Took a text file, encrypted, changed a single bit, decrypted. That one-bit change turned 10 bytes into garbage! Rest of the file was fine.
SSH has an option to use Blowfish instead of 3DES. Don't understand that algorithm well enough to say how it would handle transmission errors, and don't have time to set up a test.