Slight correction: compressing data doesn’t add entropy, it reduces redundancy. Salt is used to add entropy; it’s basically some random numbers added into mix. Reducing redundancy is important, though. Redundancy introduces patterns and predictability into the system, which is exactly what encryption schemes want to avoid.
That’s slightly more plausible, since phone numbers are at least somewhat hierarchical. It’s plausible that one might get the area code but not the exchange, or the area code and exchange but not the last four digits.
FTR, Windows NT4 passwords [classic password encryption, not the new stuff] being cracked by l0phtcrack [sp?] back in the mid-late '90s would sometimes display one password at a time 'til the whole thing cracked.
That being said, no sane individual would be using an encryption scheme like that in an intelligence application, etc…
There is no relation between cracking a code one digit at a time and reality. None. It’s nothing more than a plot device to add tension and it drives me (a software engineer) nuts.
The War Games example is especially galling. A supposedly super computer is cracking a code digit by digit and it takes something like half a minute (it’s been a while since I last saw it) to determine the last digit! It has 10 choices and it can’t figure it out! Bah!
I will go dunk my head in ice water.
Of course, for another take on it, there’s a scene in Real Genius where the heroes are trying to crack a Department of Defense password. They’ve manually entered
AAAAAA
AAAAAB
AAAAAC
AAAAAD
AAAAAE
AAAAAF
and still haven’t cracked it yet, leading one of them to comment “Man, these guys are paranoid!”.
The launch code had both numerals and letters in it, so Joshua may have had up to 36 things to try for each digit. Much harder!
But really, your point stands of course.
ISTR tyhat there was a line about the codes constantly changing. So Joshua not only has to find the right code, but the right code at the right moment.
TV Tropes calls this the Password Slot Machine. It’s also used in the video game Uplink to crack passwords.
My personal guess would be that it’s based on safes with a turn knob. You watch/listen for the first number to modify the inner mechanism, then start working on the second number, then the third, until all the tumblers have fallen and the door unlocks. This process of unlocking digits one at a time was accurate for a mechanical process, but on-screen it was updated to digital without accounting for how one would hack a real digital system. The meme was already set, so they stuck with it.
Interestingly, that site notes that some early password protection systems could be cracked that way :
Of course, today you couldn’t even touch a Word password that way, but in the 70s, when Wargames was filmed ? Who knows.
Hmm, ok, I’ll go dunk my head in luke-warm water.
See I always took it as the display on the control panel was being well controlled by the hackers to show the results of the hacking. They had an AI running that was trying to decode the password and it could decode each part of the password one by one.
That indeed may have been the case (I forget that detail about the movie), but if so, a partially cracked password would be useless when the code changed and you’d have to start all over again.
And if the code changed, “JOSHUA” wouldn’t work anymore, would it?
Nitpick: Joshua was the password, not the person doing the cracking or data entry. And the computer was the WOPR.
Thank you for asking this. I watched 24 on Monday and scoffed at it, but was told that whatever it’s based on, it’s more than I know about it and I should just be quiet. So, now I know more about it.
Yes, it’s a storytelling device to ratchet up tension. There is an alternative but it isn’t as sexy.
“Haven’t you cracked that code yet?”
“Mr. Boss, there’s three hundred trillion combinations!”
“How many have you tried?”
“Six.”
>but in the 70s Wargames was filmed ? Who knows.
Actually Wargames was filmed in 1983. DES was in use then; DES has been around since the 70s. Even by the 1970s cryptography was well past the point of simple attacks like this.
Perhaps a slight hijack, but I have seen similar activity in movies where they were trying to trace a phone number - it would show up one digit at a time but then the bad guy would hang up and they’d only have half a number.
Actually, I’ve always thought that the whole “you have to keep them on the line for so long” thing was pretty stupid as well. Is there anything real about this?
I stand corrected - but in my defense, c’mon, they still had put-the-actual-phone-on-the-mike modems back then ! And my parents, who went to engineering school in the 70s, still talk about how they used friggin’ punch cards in their computer classes. PUNCH CARDS ! That’s like, sooo Cobol 
When I was a kid, we would open poorly made bicycle cable locks this way (the kind with four rotating rings). All you had to do was yank on the cable and watch how many of the four rings shifted in position, due to the poor tolerances. Just a process of elimination.
IIRC, this was all about each digit representing a branch in the circuit, meaning that one might have to call some telephone dude in Atlanta and ask him to go through a bunch of switchgear in the back room finding the active one, and then he would call some fellow in Albuquerque, and so on.
I’m certain it didn’t work exactly that way, but I remember one of those cold case programs where they interviewed a detective who described a process like this. They even had one of the phone dudes on, describing how he would go into the back room and look for … something … and then contact the next switching station.
And now hopefully someone who knows what they are talking about will spell it out properly.
>I stand corrected - but in my defense, c’mon, they still had put-the-actual-phone-on-the-mike modems back then !
Heck, when I was a kid in the 80s we owned a 300 baud modem. We bought the one that goes straight into the phone line but I remember seeing the phone coupler models still available at the time. Why not? They worked. 300 baud gave you a lot of leeway in the noise department. For a lot of people with a single ma bell phone it made sense.
Later on, say when 1200 baud was king, the coupler came back in style when the laptop was born. I remember seeing that TRS80 laptop Radio Shack was selling with a coupler.
Old ideas work. In a few years kids will be shocked that we all ran XP as local administrator in the age of trojans and viruses. Or that many people still use dial up.