Official help for 8b
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This topic contains 191 replies, has 48 voices, and was last updated by Anonymous 3 years, 9 months ago.

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04 Jan 18 at 1:51 pm #34104
Anonymous@Cristina sorry for not replying, yes those numbers look correct.
04 Jan 18 at 3:01 pm #34106
AnonymousThanks Joan, I think I’m reversing wrong
Does anyone here have any tips for programming it on excel or word?04 Jan 18 at 3:02 pm #34108
Anonymous@cristina Remember that the matrix that you have is the ENCRYPTION matrix. To decrypt, you will need the inverse matrix of the encryption matrix.
04 Jan 18 at 3:03 pm #34109
AnonymousThat feeling when today is the last deadline and you have still got no idea on how to solve this…
04 Jan 18 at 8:02 pm #34121
AnonymousI don’t get this!!!!!!
04 Jan 18 at 8:02 pm #34122
AnonymousPlease help someone I need to complete it now
04 Jan 18 at 8:03 pm #34123
Anonymous@Lineage Noir thanks so much, I forgot, but what do you mean inverse matrix?
Thanks04 Jan 18 at 8:04 pm #34124
AnonymousWait so, you reverse each word, then you do Hill Cipher with matrices I posted before but reversed?
If yes, it doesn’t seem to work.04 Jan 18 at 9:50 pm #34133
AnonymousI’ve done everything above, reversed each word’s lettering and tried decoding it with a Hill cipher with inversed matrices. However, I get a load of rubbish back with the occasional word in it. Any clues as to what I’m doing wrong?
04 Jan 18 at 9:52 pm #34132
AnonymousText Mechanic is a very useful tool for what you suggest, and other things.
04 Jan 18 at 11:05 pm #34144
Anonymous@cristina The encryption is done by multiplying the encoding or key matrix by series of characters (or the numbers 025 representing them) Modulo 26.
Intuitively we should be able to decrypt the ciphertext dividing by the key matrix. However, matrix division is not possible, so we use an inverse matrix.
With numbers consider multiplying a number by its reciprocal 2 x ½ =1. With a matrix, when we multiply by its inverse, we get the identity matrix I. (Think of this as the matrix equivalent of 1. It is a square matrix full of zeros except the top left to bottom right diagonal which are all 1s).
Matrices in mathematics are usually on the curriculum of “A” level maths and Further Pure maths, so don’t beat yourself up if you haven’t got to grip with them (yet), congratulate yourself on the progress that you have made and maybe try one of the nonmatrix approaches.
Good luck. Tempus fugit!
05 Jan 18 at 1:47 am #34139
AnonymousCristina I don’t know if your having trouble with reversing of the words, or with the hill cipheriness.
For the reversing, I would suggest having each word on a seperate line in excel (replacing spaces with paragraph marks in word should do this)
The I would use the mid function, but instead of going 1, 2, 3, 4, go 15, 14, 13, 12… (you’ll get a few #VALUE! cells when pasted back into word, but a quick replace should get rid of these)I would then create a new spreadsheet for the hill cipher solving.
Use MID and VLOOKUP to write the cipher out in numbers (A=0, Z=25), 12 to a rowThen you’ll want to do the cipher text number – previous plaintext number. (sorry if thats not clear it’s weird to explain)
Finally use MOD(cell, 26) to convert your deciphered numbers to numbers between 025.Use VLOOKUP to convert back to AZ.
Hopefully I didn’t confuse you even more :/
05 Jan 18 at 12:15 pm #34150
AnonymousThanks so much guys, got higher than before but not 100.

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