We've done a few videos on passwords cracking passwords choosing good passwords
and I've had had a few requests both by email, and you know Twitter and on in the comments about a
choosing a password mechanism called
Dice where so I thought we'd look at this and think what's the pros and cons of this of this quite interesting system for choosing
Passwords so here's my nice unbiased casino dice that I got just for this occasion
I was quite excited apparently this-
 this dice is not biased towards rolling a six
Which actually would just mean my performance in games goes down.
When we spoke about passwords last time my hypothetical password mechanism was something like four random words with a bit of
Symbolic symbols added in maybe randomly in the middle of a word now
I chose that because I felt it was a a nice compromise between having to type something in that's really, really long or
And having something that's not too hard to remember
But also quite hard to break. Now diceware is in some sense quite similar to this scheme
But it's perhaps more mathematically defined exactly how hard it is to break. Which is why people like it?
Because I think the question comes down to in my scheme if I pick four random words
How random are Bo's worse truly if an attacker wanted to brute forth my password?
Then and they know for example that I'm using four words appended together
Then what they're going to want to do is try and work out the list of all the words
I might have used. Now, I try and throw them off a bit by using slightly odd words, but I'm a bit weird but
For the majority people let's imagine that everyone in the country
where everyone in the world is using this password scheme lots of people are going to pick really easy words you know back to the
correct horse battery staple thing
Xkcd alluded to this and we'll talk about that in a minute, but didn't necessarily answer every question
but it did get a good message across the entropy or the
Number of possible words that you've chosen is gonna differ from person to person right if one of my words
I pick is database is that because I've picked that right out at random
Or is it because it says "databases" on this book up here, and I accidentally saw it in the corner of my eye
Don't pan to the bit with no books on it
Yeah, I'm just looking at your collection of cubes 
-All solved!
That's how I roll, so what dice where does the website was established in 1995 by a guy called Weinhold from the United States
What it is is a way of using dice to ensure that
The words you're picking are actually random rather than just what you think is random and that way we have a very nicely defined
Should we say mathematical difficulty for group forcing that password?
So this is the diceware list, but I guess it's a kind of compromise between the number of dice
You just have to roll incessantly to come up with passwords and being fairly quick
but there are
7776
Words on this which is all the different combinations of five dice rolls, right? Now
So that's why I've got my nice unbiased dice
We don't wanna be accidentally biasing me towards the end of this document for example so as an example we roll the dice
It's a five. Each of these has five numbers from one to six in front of the word
Which tells you which words are going to pick. So these are the fours, I'm on to the five, says
There's the start of the fives there, then roll the dice again
It's a six, so I'm now on to the five-sixes which is here and then again
five six four
five
One five six four five one is the word
tapir
Whereas in the animal with the snout so that's the first word of my password so let me write that down
This could take a little while this is where you need to use all of your video editing skills tapir right. Let's do this again
Okay
1 3 2 1 3
If you've done this a lot of times, maybe it'd be faster 1 3 2 1 3 there. We are back up nice
5 1 3 3
What is it 1 5 1 3 3 1
How many times have you got to do this? Good question. "Rand", interesting. "R-A-N-D"
Ah, South African currency? Yeah, and also short for random, which is what we're doing now
5 2 4 6 2 RW interesting read/write, yeah, so not all of these are full words
That's one of the thing that's quite about this 3
6 having been in 2 3 exciting three six four
two
two
three six
four two two
They're guaranteed to be unbiased I think but then I got them cheaply off the internet, so I don't actually know
Okay, so let's let's stop. Let's stop there. I've done. I've got five words right now. Is this pasta really good
Well the first thing to notice
But what you don't want to do when you're picking a password is record it on video and show it on the internet
So I probably won't put this as my actual password
But there will be a few people that try nonetheless.
We've rolled the dice five times per word, we find the word and then we put spaces in between it and that's our passphrase, right?
So that is literally our password then for whatever purpose we want.
Why is this better than what I was doing? W ell, it's different, mostly. There's a few questions
we've got, right? The first is "But is this a reasonable password in terms of strength?"
Also, "How practical is it to type in?" right" It took a little while to generate
But if you're doing it a couple of times for the front end of a password manager, maybe that's not such a big deal
One thing that's worth noting is that this isn't all the words in the English language. This is this is a carefully chosen
7700 words, but a knife is short so most of the words are fewer than five characters
There's a few really short ones the idea being that even if you've got a five word or six word passphrase
It's never going to get that long you should get quite quickly typing it in
but the real benefit of this system is that these are actually random as opposed to what I've perceived to be random because
I thought of a word in my head
Which might have been a word that I happen to see on the side of a bus this morning in the previous videos we talked
about brute forcing about not you knowing what any of the characters were and how we make it easier for the attacker by using a
Dictionary of known words yeah, so this is literally providing dictionary right yeah
That's the drawback in some sense and the strength so we know exactly what words could appear in my passphrase
But even so we still can't break it because I've used too many of them so in some password schemes like
Ones where I pick words at random from a dictionary in my own brain
I'm working under the assumption, but that's secure because no else knows how it works
No one can reverse-engineer that process. That might be true, it might not be true. It depends how well you know me.
This, the process is extremely open everyone knows what the password list was
Everyone knows what my password is going to be like
But they still can't break it because it's 2 to the 64 operations
Which is too much what we don't want is security through obscurity right if I use it if I only use a 500 word dictionary
Right, that's fine as long as I keep that dictionary secret if I doesn't seem like a very good idea because then that dictionary might
Accidentally come out, and then it would be incredibly easy to break my password
So what is the strength of his password well each of these words has come from?
7776 right so we can assume that the attacker knows, but I'm using this password scheme, so they know my password is five words
separated by spaces which adds nothing because they know what the spaces are
out of a possible
7776 so the strength of this password is actually 7 7 7 6
To the 5 so another way of looking at it isn't how many bits of entropy?
Does this password have but a lot of the time?
That's how we view passwords each of these words is 12 point 9 bits so 12 point 9
times by 5 words is
64 point 5 bits which is pretty good actually that means that on average an attacker is going to have to do
about 2 - 63 - - just under 64 operations to guess your password in brute-force
That's quite a lot of operations particularly given
They're going to have to perform some hash to do this. The nice thing about this password scheme is
we know exactly how secure it is, right? As opposed to we're guessing that
the words aren't just words I know and someone can social engineer those words
and also if we want it to be more secure we can just add another word
Or another word as computational power goes up
We just add more words and we can probably remember a few words
Or if they get really long write them down and put it in our wallet. Don't lose it. I'm guessing as well
You could potentially vary the whole spaces thing right?
Yeah, so the space - the spaces thing is not hugely important the reason
it's there is because sometimes you might accidentally join two words together and them
Actually be a different word on here in which case your search has gone down to four words, right? Ao if you're being careful
That these are all actually different words, and they don't concatenate to make another word
You don't need the spaces or you could use a different character
You could also do what I did and use fewer words and
Put a random character in, right? Now on the website
He has plenty of ways of loading dice and also choosing random characters because again
when I pick a symbol
It's often
You know a star or an ampersand or an underscore
Those aren't all the characters that exist so it's a really interesting twist on picking passwords
This came about you know a few years ago now
where maybe a fork out a four word password was reasonable now in some sense you can't imagine that
Seven or eight or nine word passwords are that feasible for the majority of users that there has to be some usability
Considerations, but on the other hand five's not too bad
Or as I say four
But they make an unexpected alteration like an adding of a random symbol at a random position not between the words and that will
Significantly increase the amount of time it would take to break. You can get too carried away like with passive security
I have, and so half the time I can't login because I get my password wrong and so I've been - but
The thing you also you have to remember is that
This is way beyond a normal
Brute-force attack by someone who's just happens to have found your password hash on pastebin, right?
This is when we when we're talking about five or six word passwords where we're talking about nation state level
And you've got to really wonder whether they really care about your individual password
You might still want to secure it against them anyway. That's that's for you to decide but
They may just visit you instead
We'll put a link to the website in the description as well
So you can have a look through. He's considered almost every possible angle for this so when do you add symbols
How many words is enough for the level of security you want? It's a really good interesting
Look into password security
So I recommend you have a look
