« Extended crib | Main | last chance for 7B »
December 06, 2005
A reader writes .....
"Harry, is the following matrix correct?
12 5 11
26 20 15
4 3 10"
Apart from the question of whether this is the encryption or decryption matrix I will say that the first two entries in the top row and the last one in the bottom row are correct. Hope that helps some of you.
Posted by Harry at December 6, 2005 04:53 PM
Comments
If you wish to leave a comment please act responsibly. No personal or innapropriate comments should be made. Concerns about a comment should be emailed directly to us here. Hints about the challenges may be blocked or held back at our discretion. We reserve the right to refuse to publish comments without entering into a discussion about why, and to censor comments as we see fit. Please be patient if it takes a while for your comments to be approved.
Dangit, almost had it! Doubt we'll make the deadline now... and so close to beating Martyn! Just sooooooooooooooooooo close! *shakes fist*
Still, we got some rather ugly numbers. What were other people multiplying up by? We had to multiply up by 376 to make any sense of stuff, and even then that only applied to the crib COMRADESW - the rest was gibberish.
Posted by: Vicky Bird at December 7, 2005 03:17 PM
i actually dont think im going to complete this one, too much of a coursework buildup!!!! ahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
[Bad luck. By which of course I mean good luck with the coursework. Harry]
Posted by: martyn compton at December 7, 2005 09:35 AM
thank you harry so much for that information on how to decrypt the matrix. i have now (finally) sent in my entry. thank you so much to all the kind and helpful people over these past couple of weeks and i'm sorry harry or anyone else that i waqs constantly pestering and asking questions. =)
Posted by: laura at December 6, 2005 11:53 PM
alex's program brought me back to the dark ages where i used to program in VB6
of course, ive moved onto greener pastures now; ruby and python :P
chidders
Posted by: chidders at December 6, 2005 10:55 PM
Insane, what table? A mod 26 multiplication one?
Posted by: Ruth at December 6, 2005 10:52 PM
Don't bother trying to find the decryption matrix by inverting the encryption matrix.
Just brute force the equations you get,
e.g. in Visual Basic (there are supposed to be indents, but HTML doesn't allow more than one space at a time, and I don't know if tabs are allowed either):
' To find the top row of the decoding matrix
' |a b c|
' |d e f|
' |g h i|
Dim a As Integer, b As Integer, c As Integer
For a = 0 To 25
For b = 0 To 25
For c = 0 To 25
If ((18 * a + 18 * b + 14 * c) Mod 26) = 2 Then
If ((3 * a + 19 * b + 20 * c) Mod 26) = 17 Then
If ((16 * a + 14 * b + 4 * c) Mod 26) = 18 Then
' Save a, b and c
' There are only 4 different solutions
EndIf
EndIf
EndIf
Next c
Next b
Next a
' And so on for d, e, f, g, h and i
Posted by: Alex at December 6, 2005 10:41 PM
ummm....
i seem to have done everything right, but the table is now giving me completly random numbers
wot is going wrong?
Posted by: Insane (FHS) at December 6, 2005 09:27 PM
how do i invert a matrix/find a decryption matrix from a working coding matrix
as in, i have the correct matrix to code it, but need to work out the matrix to decode it!
[Great! see my remarks on another post this evening. Harry]
Posted by: Insane (FHS) at December 6, 2005 09:17 PM
Help just more confused i cant seem to get any equations!
Posted by: freaks at December 6, 2005 08:49 PM
harry, i think i have perfected my matrix. yet i still cannot inverse it. i need urgent help. why is no one else writing? have they all finished? i am so useless at maths. i am a year 10, but i bet some year 9s or younger have already cracked this one, i feel dumb...
No you are not dumb. To invert the matrix you need to do the following:
The inverse of the matrix
a b c
d e f
g h i
is
km kn ko
kp kq kr
ks kt ku
where the entries are given by
m = (ei-hf), n=(fg-di) o=(dh-ge)
p=(ch-bi) q=(ai-gc) r=(bg-ah)
s=(bf-ec) t=(cd-af) u=(ae-bd)
and k is the number you need to multiply k' by to get 1 mod 26 where
k'=a(ei-hf)-b(di-gf)+c(dh-eg)
unless I have made a mistake of course! Harry]
Posted by: laura at December 6, 2005 08:17 PM
can u give us the rest of the crib pleeease
Posted by: freaks at December 6, 2005 08:00 PM
Oh... I got 4 3 10 for the last row as well! What can i do? i mean it fits in 6 ohter equations!I don have much time left. Help, please?
[Ah, I see. I hadn't noticed that ssome of you may be multiplying the vector on the left so you get the transpose of the matrix I worked with. That means my last comment was misleading, and 4 3 10 does work. Harry]
Posted by: Sam at December 6, 2005 07:31 PM
so 4 ans 3 is not correct?
Posted by: Sam at December 6, 2005 07:09 PM
Harry, a question.
Does the 8B cipher involve anything that is not explicitly contained in this list?
Cryptology
History, Maths, Science etc.
Rotor
Scrambler
Wheel
Mechanism (inc. Ratchets etc.)
Electricity
Keyboard + Input
Printer + Output
Lamps
Connections
Contacts
Plugboard
Switches + Levers ...
Notches
Rotor advance blocking pins
Reflector
Rings
English
A-Z + Numbers
Any other symbols/markings/indicators
Clock/Counter
I suppose this is only useful if you say no! Oh, the possibilities.
[Luck? Harry]
Posted by: Jason at December 6, 2005 05:49 PM