Jammed keysafe. Grrr.....

[dennis]

The post you replied to, as in the quote you have included, states "with a 4 digit dial type" you get 10000 codes and you can use each digit more than once on them.

[The Medway Handyman]

Keysafe say 1024.

[The Medway Handyman]

And that most elderly people use their year of birth as the code.

[Dave Liquorice]

English comprehension is not a strong point is it?

What is so hard about:

"The dial type was only mentioned to get the maximum number of permutations from 4 digits."

and:

"The rest of the probabilty post is about push button like the push button key safe mentioned at the start of the thread."

[mike]

Ah, yes:

I assume this is how they've arrived at that figure:

If there are ten buttons and each can be in one of two states ("on" or "off "), then 2 raised to the power 10 would give 1024 (and that would explain w hy the new 12-button safe has 4096 combos: 2 raised to the power 12). But it fails to point out that multiple combinations will open the safe.

And I don't see why their methodology is right and mine is wrong.

But if they are right and there are only 1024 possible combos --- and there are 24 codes that will work --- the probability of guessing one of the cod es is even higher.

[John Williamson]

Damn! I thought that would be a nice secure number to use.... (Only joking.)

[dennis]

Do i really need to repeat whole posts you have made to prove you are wr >> With a 4-digit dial-type key safe, there is a total of 10x10x10x10 = >> 10000 possible combinations of which only one will work. > > It's simpler than that: any whole number between 0000 and 9999. So, yes, > 10000.

*Maximum* of 10000 but you are forgetting that you can only use each digit once and that the digits can be entered in any order so 1234 is the same as 2134 or 2314 or 2341, etc, etc...

I'm not sure that the odds of entering the working code are 1 : 210 from the other post. I'm not a statastion or probabilty expert but have a sneaky feeling there is even more to it than meets the eye.

......... End quote

Now where exactly does it say its anything other than a four digit dial type and why do you think it can't use all the digits fro zero to nine on any dial and that the order doesn't matter?

If anyone can't comprehend its you. Stop wriggling.

End of it!

[The Medway Handyman]

As I may have mentioned before, my daughter is a paramedic in London. Whenever they get a "grey lady down" call, if they haven't been given the code, they ask a neighbour how old the person is & try the year of birth. Apparently in works in 8 out of 10 cases :-)

[The Medway Handyman]

That's cheating!

As others have said, worn buttons are a dead give away. Also 1,3,7,9 which are the four corners and, on electronic ones 1,4,4,7 - 2,5,5,8

-and 3669 (straight down, with centre repeated).

[The Medway Handyman]

until I could get over and instal a permanent one. It's this one:

stiff as it was new.

push in and the keys are stuck inside it.

increasingly confused, 97-year old relative spots them and lets them in (or not).

wretched thing is on loan to Social Services from another department and they're reluctant to do anything that might damage it in case they're not lent any more.

newsgroup but does anyone have any ideas I might try to get the swine working again. I know the code.

someone with a temperature to whom the police sent round a social worker with a megaphone to try and talk it down.

AAMOI, about 3 years ago I applied to be the approved installer for Keysafe in the ME postcodes. I still am AFAIK.

Filled in numerous forms, sent copies of my PLI & CRB + a photo. Got a certificate & identity badge back & waited for the jobs to roll in.

I'm still waiting. Not one single job in 3 years.

Mind you, at £48 a pop I'm not surprised.

[Vir Campestris]

Let me work it backwards. There's a 4/10 chance of the first button you press being one of the combination ones, then 3/9, then 2/8, then 1/7.

So your chance of getting it right is (4*3*2*1)/(10*9*7*8). That's 1 in 210.

Andy

[SteveW]

I've not yet reached that age (or that sex!), but no-one would have any chance of guessing a link to my PIN of choice for alarms, access, etc. - when I first needed one, I used the digits of an electronic component that I was experimenting with at the time!

SteveW

[SteveW]

it open last night... so they have put the keys back in on the basis that it's probably just a bit stiff. Oh, jeez...

theory) but one number just wouldn't depress.

of O-Level probability:

possible combinations of which only one will work. So probability of entering working code by chance is 1 in 10000.

sequence, the total number of possible combinations is 10x9x8x7 = 5040, and (because the digits can be entered in any sequence) the total number of working codes is 4x3x2x1 = 24, so 24 codes in a total of 5040 or probability of entering working code by chance is 1 in 210.

First button, 4 in 10 chance, second button 3 in 9 chance, etc.

1 / (4/10 x 3/9 x 2/8 x 1/7) = 210.

SteveW

[mike]

Having thought about this some more, I've concluded that the numbers on the push-button safe are a red herring as far as probability goes.

On the dial safe, you have four dials and each of those dials can be in any of ten positions (0-9). Additionally, the four dials must be in the one programmed sequence. Imagine laying out four suits of cards (minus the pi cture cards) and being able to choose any combination of one from each suit e, left to right.

Now on the push-button safe, each button (or dial) only has two possible po sitions, on or off. It's like one suit of cards and the only combination c hoice you have is face up or face down. That's far fewer combinations. Be cause the numbers don't come into play, one face up card is the same as any other face up card.

So I think Keysafe's calculation of total permutations is correct, and mine is wrong because it assumes a sequence that isn't there.

Does that make sense?

With regard to possible opening combinations, I think both you and I have a gain assumed a sequence that isn't there. There's no 4x3x2x1 because there isn't a *sequence* of four numbers. There are ten buttons, each with a bi nary choice.

So the chances of you getting the first button right is 1 in 2, the chances of getting the second right is also 1 in 2 and so on. This works out as 1 /(2 to the power 10) with is 1/1024 which means there is only one combinati on that will work --- and that is to get all four right (but the order that you push them in doesn't matter).

Again, think of a suit of cards, 6 face up, 4 face down. It doesn't matter which order you turn them in as long as you get the same four face up.

Plausible? Correct? Or a load of old cobblers?

[Bob Eager]

I used to use one that was the last four digits of a long defunct phone number that meant a lot to me....

[Bob Eager]

I asked a tame mathematician today and she said it was 210 straight away.

[dennis]

I always set a five or six digit code to beat the ones that think they only have four digit codes. It works.

The one described is a cheap (less than £20) key safe (unless you pay the £48 SSP some people charge), there are better ones about for about £45.

My local authority no longer fits the type in the photo and hasn't for a few years.

[Dave Liquorice]

The "numbers" do come into play as once you have used a "number" from one of your four stacks of cards you can't use it from any of the remaining stack(s).

50:50 where does that come from? You have ten buttons and any four buttons could be correct so isn't that 4 from 10? (1:2.5), next choice is 3 from 9 (1:3), then 2 from 8 (1:4) and finally 1 from 7 (1:7)? 2.5 x 3 x 4 x 7 = 210

Curiously 2.5 x 2.5 x 2.5 x 2.5 = 39.0625 which is odd but possibly not surprising as odds and probabilties are not particularly intuative.

[Bob Eager]

The optimum would appear to be a 5 digit code - the odds go to 1 in 252. With a six digit code they go back to 1 in 210.

[The Medway Handyman]

There is a very old gambling scam called the Six Card Swindle.

Two picture cards and four spot cards are face down & mixed up. Both players place £1 into the pot & the punter turns over any two cards.

You explain to him that even though its 2-1 in his favour, you will play even money.

If one or both are picture cards, he loses & you take the pot.

If both are spot cards, he wins the pot.

Played as a 'freeze out' bet. You both start with £10 & play till one of you runs out of money - it will be the punter.

I have earned loads of free beer on this :-)