General :: Unconvert Text File From Binary Format

I've got a rather large CSV file (~700MB) which I know to consist of lines of 27-character alpha-numeric hashes; no commas or anything fancy. Somehow, during its migration from Windows to Linux (via winSCP and then a few regular SCPs), it has converted into some kind of binary format I am unfamiliar with.If I open the file in vi, everything appears fine, and it says [converted] at the bottom, although I know it's not a line endings issue (and dos2unix doesn't help). If I 'head' the file, it looks proper except for a " at the beginning of the first line. If I open up the file in nano, however, I see the at the start and then "^@" before every character (even newlines and EoF).

If I try to re-save or copy the file (say via: head file.csv > short.txt), this special encoding is preserved. I copied the first ten lines out of vi (which displays it properly) into my Windows clipboard via my SSH client, then pasted it into a new text file, test.txt. This file is visually identical when opened in vi (and similar through 'head', minus the ), although it's roughly half of the filesize. I have no idea what format this once-text file got converted to (it's notoriously hard to search the internet for symbols), but surely there must be some way to convert it back.