Switched output

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Switched output

calccrypto 29 Nov 2009 18:50

im writing another encryption algorithm, and it involves expanding the key.

to make the decryption keys, the encryption keys are made first, and then edited
on the computer, i labeled the keys 0-51, rather than 1-52,so every index is 1 less than the indexes shown below

s49*  s50#  s51#  s52*  s47  s48
s43*  s45#  s44#  s46*  s41  s42
s37*  s39#  s38#  s39*  s35  s36
s31*  s33#  s32#  s34*  s29  s30
s25*  s27#  s26#  s28*  s23  s24
s19*  s21#  s20#  s22*  s17  s18
s13*  s15#  s14#  s16*  s11  s12
s7*   s9#   s8#   s10*  s5   s6
s1*   s2#   s3#   s4*

sXX* = multiplicative inverse of sXX modulus ((2^16)+1)
sXX# = additive inverse of sXX modulus (2^16)

for x in range(8):
    key += [invmod(temp[48-6*x]),
            two_comp(temp[50-6*x]),  # i know these 2 are switched, but for some reason, 
            two_comp(temp[49-6*x]),  # they give the right outputs for the others
            invmod(temp[51-6*x]),
            temp[46-6*x],
            temp[47-6*x]
            ]
key += [invmod(temp[0]),two_comp(temp[1]),two_comp(temp[2]),invmod(temp[3])]
 
# invmod is multiplicative inverse
# two_comp is additive inverse

---

This is what im getting:

0011 2233 4455 6677 8899 aabb
ccdd eeff 6688 aacc ef11 3355
7799 bbdd fe00 2244 99de 2266
aaef 3377 bbfc 0044 88cd 1155
cd55 de66 ef77 f800 8911 9a22
ab33 bc44 cdde eff0 0112 2334
4556 6778 899a abbc e002 2446
688a acce f113 3557 799b bddf
8cd1 1559 9de2 266a

---

This is the correct output

0011 4455 2233 6677 8899 aabb
ccdd eeff 6688 aacc ef11 3355
7799 bbdd fe00 2244 99de 2266
aaef 3377 bbfc 0044 88cd 1155
cd55 de66 ef77 f800 8911 9a22
ab33 bc44 cdde eff0 0112 2334
4556 6778 899a abbc e002 2446
688a acce f113 3557 799b bddf
8cd1 1559 9de2 266a

Can anyone tell me why this is happening?

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Last edited on 03 Dec 2009 02:10 by calccrypto Show more

Re: Switched output

Matthias1992 02 Dec 2009 20:32

Hmm I think you mean why there are some outputs swapped? O well yea, I just read the title…hehe pretty self-explainatory.
so s49* should be

[
invmod(49)
]

?

well anyway, I am am not an expert on encryption but I do think the s47 till s6 might screw up some things…
Well thats not much of a solution…can you figure out which "s" 4455 and 8899 are? Also I rather quickly noticed that 2233 and 4455 and 8899 are numbers with repetition in them, perhaps that causes a problem. One last question: is this python? It looks like it….

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Re: Switched output

calccrypto 03 Dec 2009 02:18

oh. the first line is repetitive because the key was "00112233445566778899aabbccddeeff", and its just expanded twice (once for the encryption key, and then changed into the decryption keys)

and what do you mean it might s47-s6 might screw up? is it because the key might be edited by the previous index? nope. it takes the encryption key and finds its 'opposites' (in sets of 16 bits)

and yes, this is python

---

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