I'm unsure if your script has similar functionality or if yours does something more. I'm very new to scripting and kind of new to Greyhack. Been playing off and on for a while, through several major patches.
Your post is a bit old so it's entirely possible that your problem was solved via newer in game methods.
Here is the script that I was able to build to concatenate an entire file of passwords. Similar to the first time you're shown passwords, you need to place your username and passwords in a single line in a text file. I did not code any error catches but if the format is followed it places everything into a map and you can decode the entire file instead of one at a time. Unsure of the code syntax.
[code]
pc = get_shell.host_computer
filetodecode = home_dir + "[directory for the file to decode]"
content = pc.File(filetodecode).get_content
content = content.split("\n")
passwordlist = {}
for each in content
	sliceto = each.indexOf(":")
	user = slice(each, 0, sliceto)
	encodedpass = slice(each, sliceto+1)
	decipheredall = include_lib("/lib/crypto.so").decipher(encodedpass)
	passwordlist[user] = str(decipheredall)
end for
print passwordlist
[/code]