Comments on: Keep your iPhone secure by keeping it clean

By: Garrick Chow, senior trainer and evangelist

Garrick Chow, senior trainer and evangelist — Tue, 09 Mar 2010 23:56:11 +0000

Hi LX Developer,

You are absolutely correct! It’s 1 in 36. My mistake was thinking that there would still be four choices for which digit was repeated when it is only three choices. My other mistake was majoring in English instead of Math in college. Thanks for the catch!

It’s interesting to me that having a 3 digit code is still more secure than having a four digit code. But I guess it makes sense since having three smudges instead of four gives you less info to work with.

By: LX Developer

LX Developer — Tue, 09 Mar 2010 22:04:03 +0000

In your footnote, wouldn’t the odds of guessing the PIN with three smudges be 1 in 36? Let’s say the smudges were on the numbers 1, 2, and 3. If the 1 were repeated, the combinations would be 4!/2! = 12. There would be an additional 12 combinations if the 2 were repeated and 12 if the 3 were repeated for a total of 36.

By: UK Web Designer

UK Web Designer — Thu, 11 Feb 2010 11:56:04 +0000

WOW !! I just tried this with an unsuspecting colleague – first I asked if I could look his iPhone over – as it was locked he tapped in his PIN – which I didn’t see – once I had the phone in my hands I said I’d guess his PIN – say 4 prints and said what I thought was his four digits ! He looked surprised but said he was not telling – so I said OK lock it again and I’ll try – it took me 9 goes !!! Needless to say my colleague nearly dropped to the floor !!! (I did tell him how I guessed WOooooWWWW !!

By: Cristina

Cristina — Fri, 05 Feb 2010 17:48:52 +0000

Wow! That’s an eye opener! Good think I am always wiping my screen clean. I can’t stand those smudges.

By: Laurie

Laurie — Thu, 04 Feb 2010 18:16:55 +0000

I don’t know what this person has on their fingers? Grease from eating french fries all the time. Anyway, I pass-code protect my iPhone and there are no finger prints on the screen.