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Reversing Shift-XOR operation
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Topic: Reversing Shift-XOR operation (Read 313 times)
DARKER
[SCF]
Administrator
Senior Member
Posts: 336
Reversing Shift-XOR operation
«
on:
October 20, 2015, 07:20:21 AM »
Minule som nieco podobne potreboval, mozno sa to niekomu hodi. Ako vypocitat povodnu hodnotu na ktoru bol pouzity SHR a XOR
https://krypt05.blogspot.in/2015/10/reversing-shift-xor-operation.html
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pr0p4g4nd4
[SCF]
Senior Member
Posts: 429
Re: Reversing Shift-XOR operation
«
Reply #1 on:
October 20, 2015, 08:09:42 AM »
az sa mi nechce verit, ze niektomu by nebolo jasne, ze ako je v tom linku shr s hodnotou 10, to je len delenie hodnotou 1024 a xor je len viacmenej scitavanie.
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Aký je rozdiel medzi mladým a starým chlapom?
Mladému behá piča po rozume, starému po byte...
Kto robí je robot, kto koktá je.. koktavý!
DARKER
[SCF]
Administrator
Senior Member
Posts: 336
Re: Reversing Shift-XOR operation
«
Reply #2 on:
October 20, 2015, 08:33:28 AM »
No nie celkom, nezabudaj ze pri SHR sa ti stracaju byty
Priklad SHR(10110011010011111100010010011111, 10)
1011001101001111110001 > 0010011111 - 0010011111 je stratene
0000000000 > 1011001101001111110001 - 0000000000 sa prida na zaciatok
teda napriklad 2 rozne cisla budu mat ten isty vysledok
1011001101001111110001-0010011111 = 0000000000-1011001101001111110001
1011001101001111110001-1111111111 = 0000000000-1011001101001111110001
cize 2^10 cisel bude mat ten isty vysledok (1024 hodnot)
jedina sanca je je tych 10 bytov vybrtutovat... XOR je jasny tam vies zistit povodnu hodnotu ...
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pr0p4g4nd4
[SCF]
Senior Member
Posts: 429
Re: Reversing Shift-XOR operation
«
Reply #3 on:
October 20, 2015, 09:00:53 AM »
samozrejme, ze som reagoval na ten konkretny priklad v clanku, tam je to presne tak ako pisem. v pripade, ze sa shr-uje nejake nie konstantne cislo, tak sa cast informacie strati (resp moze stratit).
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Aký je rozdiel medzi mladým a starým chlapom?
Mladému behá piča po rozume, starému po byte...
Kto robí je robot, kto koktá je.. koktavý!
Kockatá hlava
Junior Member
Posts: 134
n00b
Re: Reversing Shift-XOR operation
«
Reply #4 on:
October 20, 2015, 11:25:22 AM »
DARKERe, zalozil sis blog? Vsichni ted teda cekame dalsi zajimavy clanky!
EDIT: hmm, nevypada to, ze to ses ty, tak nic...
«
Last Edit: October 20, 2015, 11:34:04 AM by MazeGen
»
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DARKER
[SCF]
Administrator
Senior Member
Posts: 336
Re: Reversing Shift-XOR operation
«
Reply #5 on:
October 20, 2015, 11:40:04 AM »
Nie, nie :-) ziadny blog, iba zuajimavy clanok z netu :-) Ale obcas si vravim ze by nebolo zle sa obcas podelit so skusenostami :-) Mozno vam sem hodim nabuduce skusenosti so Z3 SMT Solver
https://github.com/Z3Prover/z3
- veeelmi dobra vec na riesenie niektorych problemov v RE.
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Kockatá hlava
Junior Member
Posts: 134
n00b
Re: Reversing Shift-XOR operation
«
Reply #6 on:
October 20, 2015, 09:17:22 PM »
Uz jsem rikal RubberDuckovi a dalsim, ze to v CZ/SK s publikovanim okolo RE a asm dost skomira, takze co se tyce me, rad si prectu vsechno, co napises. Treba ty solvery jsou hodne zajimava vec.
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Reversing Shift-XOR operation