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cracking OTP

Name: Anonymous 2013-05-15 11:43

Suppose two english language messages A and B are encrypted with the same one time pad P: X=A^P and Y=B^P.

Then X^Y=(A^P)^(B^P)=A^B so we can try to guess which words are in A and B and xor it with that to see if we get a word back to chip away at decoding the cyphertext.

The difficulty is that the words overlap, they don't line up easily. For example the messages might be like this:

---- ---------- --- ----- -------- -------- -------
-- ------ ------- ---- ---- --- ------ -------- ---

Name: Anonymous 2013-05-15 11:48

fine!

Name: Anonymous 2013-05-15 12:30

Isn't this why they're called `one time pads'?

Name: Anonymous 2013-05-15 15:36

stop playing with computers and go FUCK real women

Name: Anonymous 2013-05-15 17:13

>>4
but computers are fun

Name: Anonymous 2013-05-15 17:17

>>4
my computer isn't a girl you bastard

he's a real man's man

Name: Anonymous 2013-05-15 17:38



    [b][o][u]
    [sup]A[sup]T[sup]ORI[/sub][/sub][/sub][/sub][/sub]
    [/u][/o][/b]

Name: Anonymous 2013-05-15 17:45

>>7
go practice saged in a thread on page 600 or so.

Name: Anonymous 2013-05-15 18:10

>>8


fuckyounerd

Name: Anonymous 2013-05-15 20:57

It's all in the ASCII

Name: Anonymous 2013-05-15 21:04

..otherwise you could crack two pads that encrypted the same message =)

Name: Anonymous 2013-05-15 21:21

>>4
die heteronormative scum

Name: Anonymous 2013-05-15 21:49

>>1
What if it's not English?

>>10
What if it's not ASCII?

>>12
What if it's not normative?

Name: Anonymous 2013-05-15 21:56

Why would you use a one time pad more than once, you one-man, special needs daycare?

Name: Anonymous 2013-05-15 22:07

>>14
Why does your sentence, flower pot, it's very comfy?

Name: Anonymous 2013-05-15 22:16

>>15
Has there been ever a think like as far to?

Name: Anonymous 2013-05-15 22:22

>>13 not sure...

>>10 actually i still think this might even work...
If we forget about truly random numbers... and just expect a simple prng and two random seeds, then it should reduce to simply having a long enough message to crack ^^ tadaa
for example, two 8-bit lsfr (lfsr?) will repeat every 255 bits, and there will be 255*254 pairs of seeds..
then you just need to match the sequence =D

Name: Anonymous 2013-05-15 22:39

What's your OTP, /prog/? Mine is Cirno\Agni Cirno. The contest of fire and ice, I just love it!

Name: Anonymous 2013-05-15 23:14

...well, having a long enough message + resources to compute enough prng streams.. lfsr's are good because each seed is basically just the same sequence with a different offset...
and the attack gets better if the lfsrs aren't of the same size =)

Name: Anonymous 2013-05-15 23:17

>>17-19
op here, thank you man

but could you please remove the emoticons, they make your message look unprofessional

Name: Anonymous 2013-05-15 23:19

>>18
There are millions of Tohos and you pick fucking Cirno out of all those?

I think this thing of "Cirno" being posted everywhere is just an elaborate troll from Re/g//g/it.

Name: Anonymous 2013-05-15 23:29

>>21
Cirno's awesome, fuck you! She's cute and sweet (sometimes), yet she can beat the shit out of the other fairies and kinda hold her own against Marisa for a little while.

Name: Anonymous 2013-05-16 0:58

aww... i was just happy cos i was breaking two pads at once ^^

Name: Anonymous 2013-05-16 1:01

...and it's a proper OTP break rather than a reused pad

Name: Anonymous 2013-05-16 1:48

>>20
I am the fucking OP, you just [b]FUQIN ANGERED[/o] me by claiming to be me. If you keep doing this I'll PGP sign my messages.

Name: Cudder !MhMRSATORI!fR8duoqGZdD/iE5 2013-05-16 2:23

The other type of OTP is easy to crack... http://www.mcu-crack.com/en/services_code_extraction.html

Name: Anonymous 2013-05-16 3:11

i wanna fuck ur brains out

Name: Anonymous 2013-05-16 5:30

Copyright Shanghai Vegan Research 2003.

Name: Cudder !MhMRSATORI!fR8duoqGZdD/iE5 2013-05-16 6:29

>>28
I have not asked if they don't eat meat.

Name: Anonymous 2013-05-16 6:39

>>1
i guess if they didn't encrypt the spaces it would be a bit more difficult..
but the overlap should probably be more of a help than an obstacle? (also helps if you know how long each word is... but probably not that lucky)
maybe just run like a letter-pair/byte lookup (~26*256*2? bytes) over the strings looking for words from a dictionary

Name: Anonymous 2013-05-16 6:45

so the first A^B might be 0, and have ooh, all pairs so
a/a
b/b
...
z/z
(both first letters are the same)

i guess you'd probably really want to look for the most limited pairs first and try to work backwards

Name: Anonymous 2013-05-16 8:21

>>15
You're also a one-man special needs daycare. b2/g/ leller

Name: Anonymous 2013-05-16 9:07

>>32
Go back to English 101, please.

Name: Anonymous 2013-05-16 10:20

>>33
please, please.

Even though it is a textboard, one must mind their manners and tone of voice.

Name: Anonymous 2013-05-16 10:26

>>34
LLLLLLLLLLLLLLLEEEEEEEEEEEEEELLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
>EGIN WIN GROSKI

Name: Anonymous 2013-05-16 10:34

>>33
I have nothing to prove to you, anglophonic piece of shit I fucking hate you.

Name: Anonymous 2013-05-16 10:49

>>36
Good, good, let the burrhurt flow through, let in envelope you, let darkness shroud your heart, allow the darkness to become your salvation. Only then can you become a true avenger.

Name: Anonymous 2013-05-16 10:51

>>37
back to /g/ anglo cunnard ASFSFAGSGDAFGAHAFKAFHALAFAFASHAFLGHAGASAGHASSDJFAFHAFHAG I FUCKING HATE YOU

Name: Anonymous 2013-05-16 11:08

>>36-38
I'm going to cumard in yo'ure anuses.

Name: Anonymous 2013-05-16 11:18

>>38
Good little brother. Sustain the rage. You are now on a path the rest of you can't follow. Feel the butthurt running through your very veins. You are an avenger.

Name: Anonymous 2013-05-16 11:22

>>40
10/10 best new /prog/rider

Name: Anonymous 2013-05-16 11:52

AAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHHHHHHRRRRRRRRRRRHHHHHHHHHHHHHH
LE ENCULER FAIR!!!
LE ENCULER FAIR!!!!
LE CONNARD ANGLO LE ENCULER FAIR I FUCKING HATE YOU AGDFS GFD GDFAGDSFSDFSDD DIE IN A FUCKING FIRE CONNARDENCULER FAIR

Name: Anonymous 2013-05-16 13:57

>>42
So it begins. Just as I once did little brother, you to have long since closed your eyes. Your only goal now lurks in the darkness.

Don't change these.
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