Avril Coghlan <[email protected]> writes:
> Dear all,
>
> I'm trying to figure out how to make a multiplicative cipher in SAGE.
> For example, to make a multiplicative cipher:
> M_9{m} = 9 x_{26} m
> and to use it to encipher the text 'HAPPYNEWYEAR', I tried typing:
>
> A = AffineCryptosystem(AlphabeticStrings())
> P = A.encoding("HAPPYNEWYEAR"); P
> a, b = (9, 0)
> C = A.enciphering(a, b, P); C
>
> I get back:
> LAFFINKQIKAX
>
> However, I think I should get back:
> TINNQVSYQSIF
> assuming A=1, B=2, C=3, D=4.... Y=25, Z=26
Well, it's zero-based, actually. So A=0, B=2, ... Z=25. You can test
this as follows:
sage: A = AffineCryptosystem(AlphabeticStrings())
sage: A.enciphering(1, 0, A.encoding('abcd'))
ABCD
sage: A.enciphering(3, 0, A.encoding('abcd'))
ADGJ
As you can see, A remains unchanged when the offset is 0, whereas B (1)
becomes D (3) when multiplying by 3.
Hope that helps.
-Keshav
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