My Grandma sent me a text recently, even though she struggles to type what she means accurately (she accidently taps the keys more times than she needs to):

$\hskip2in$enter image description here

She used to be a code-breaker back in WW2, so she's always enciphering things, I suspect she may be sending me a code of some kind to crack...

What should I send back to her?


Hi Melkor!
Just got my new mobile & it's gr8!
Could you help me find what computer i should get?


(Not part of the puzzle)

I have tried to make this cipher as original as I can, so have fun and good luck! Brute-forcing this cipher will not work, this is a new cipher idea, and the clues in the puzzle will help you understand it.


Grandma's new phone looks like this

enter image description here

  • $\begingroup$ Does Cb refers to her name here, also please mention what war are you referring to? $\endgroup$
    – ABcDexter
    Feb 4, 2017 at 15:57
  • $\begingroup$ Cb stands for code breaker, which I have already stated in the clue. As for the war, it was WW2. $\endgroup$
    – Melkor
    Feb 4, 2017 at 19:12
  • 1
    $\begingroup$ >! Looks like it's a playfair cipher (en.wikipedia.org/wiki/Playfair_cipher). >! The key is figuring out what the key should be. >! I tried "grandma melkor" but got garbage. $\endgroup$ Feb 5, 2017 at 6:26
  • $\begingroup$ @bill kidder no the cipher is more creative, you will not need to brute force it. $\endgroup$
    – Melkor
    Feb 5, 2017 at 8:53
  • $\begingroup$ My memory is failing so I may be wrong, but I didn't think my old Nokia phone was able to send text messages. (Maybe it's just that I didn't know anyone else with a phone which could receive text messages, so I just used the phone as a phone.) Just googled - it did handle SMS - must have just been me not knowing anyone to send a message to. $\endgroup$
    – YowE3K
    Feb 5, 2017 at 19:27

1 Answer 1


The word is

COLOSSUS - a set of computers developed by British codebreakers in 1943-1945.

enter image description here

since she

taps the keys more times than she ought to, the number sequence arising from the Nokia key matrix is $67, 79, 76, 79, 83, 83, 85, 83$ and this represents in ASCII COLOSSUS.

  • 1
    $\begingroup$ Well Done solving! $\endgroup$
    – Melkor
    Feb 5, 2017 at 19:21

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