What algorithm and key is this message?

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What algorithm and key is this message?

Post by ghostheadx2 on Tue May 19, 2015 1:50 pm
([msg=88116]see What algorithm and key is this message?[/msg])

So, here is a message that I need to decrypt:

Code: Select all
dkn yjdkqcluydlqb tqwn lf leeiyxnyiybqjdqozqj

endf rnd wqmb dq hjflbnff
dq wnonyd dkn kjbf
wlw dknz fnbw in wyjrkdncf mknb l yfxnw oqc fqbf
zqjcn dkn fywwnfd hjbtk l npnc ind
hjd zqj tyb hnd hnoqcn mncn dkcqjrk
ilfdnc lee iyxn y iyb qjd qo zqj

dcybgjle yf y oqcnfd
hjd qb olcn mldklb
qbtn zqj olbw zqjc tnbdnc
zqj ycn fjcn dq mlb
zqjcn y fvlbnenff vyen vydkndlt eqd
ybw zqj kypnbd rqd y tejn
fqinkqm lee iyxn y iyb qjd qo zqj

li bnpnc rqbby tydtk iz hcnydk
fyz rqqwhzn dq dkqfn mkq xbnm in
hqz myf l y oqqe lb ftkqqe oqc tjddlbr rzi
dklf rjzf rqd ni ftycnw dq wnydk
kqvn kn wqnfbd fnn clrkd dkcqjrk in
bqm l cnyeez mlfk dkyd l xbnm kqm dq fmli

hn y iyb
mn ijfd hn fmlod yf y tqjcflbr clpnc
hn y iyb
mldk yee dkn oqctn qo y rcnyd dzvkqqb
hn y iyb
mldk yee dkn fdcnbrdk qo y cyrlbr olcn
izfdnclqjf yf dkn wycx flwn qo dkn iqqb

dlin lf cytlbr dqmycw jf dlee dkn kjbf ycclpn
knnw iz npncz qcwnc ybw zqj ilrkd fjcplpn
zqjcn jbfjldnw oqc dkn cyrn qo myc
fq vytx jv rq kqin zqjcn dkcqjrk
kqm tqjew l iyxn y iyb qjd qo zqj

hn y iyb
mn ijfd hn fmlod yf y tqjcflbr clpnc
hn y iyb
mldk yee dkn oqctn qo y rcnyd dzvkqqb
hn y iyb
mldk yee dkn fdcnbrdk qo y cyrlbr olcn
izfdnclqjf yf dkn wycx flwn qo dkn iqqb

hn y iyb
mn ijfd hn fmlod yf y tqjcflbr clpnc
hn y iyb
mldk yee dkn oqctn qo y rcnyd dzvkqqb
hn y iyb
mldk yee dkn fdcnbrdk qo y cyrlbr olcn
izfdnclqjf yf dkn wycx flwn qo dkn iqqb


I need to know what key and algorithm this message is in. Don't tell me the message. Also, I need to know what is the difference between base64 and hexa? Thanks.
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Re: What algorithm and key is this message?

Post by Turn on Tue May 19, 2015 1:53 pm
([msg=88117]see Re: What algorithm and key is this message?[/msg])

At a quick glance, this looks like a substitution cipher to me. That means the replacements can be completely arbitrary and you need to do frequency analysis.

-- Tue May 19, 2015 1:54 pm --

I've solved this cipher in less than 2 minutes, it is in fact a substitution cipher.
For verification think of Mulan
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<cen> .lua print ('Tsyn 9.47.-u 3 12 5')
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Re: What algorithm and key is this message?

Post by ghostheadx2 on Tue May 19, 2015 2:43 pm
([msg=88120]see Re: What algorithm and key is this message?[/msg])

I don't get the Mulan clue. Nonetheless, I'm having a lot of trouble deciphering it. Lol. I found this guide through google:

http://www.dummies.com/how-to/content/cryptography-101-basic-solving-techniques-for-subs.html

I think I'm going to find another guide myself, because this is taking forever. Could you give me a more understandable hint? Here's some of what I got when Googling it:

http://www.dummies.com/how-to/content/c ... -subs.html

http://www.ti89.com/cryptotut/substitution.htm

The first link I posted went into decryption, but a lot of the results I got were like the second one where it just described what the substitution cipher was and how to code it. I'm thinking of writing down the number of occurrences of each four, three, and two letter word, in a word doc, and trying to use that. In fact, I think imma do that right now. Is that a good strategy?
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Re: What algorithm and key is this message?

Post by pretentious on Wed May 20, 2015 5:43 am
([msg=88122]see Re: What algorithm and key is this message?[/msg])

ghostheadx2 wrote:The first link I posted went into decryption, but a lot of the results I got were like the second one where it just described what the substitution cipher was and how to code it. I'm thinking of writing down the number of occurrences of each four, three, and two letter word, in a word doc, and trying to use that. In fact, I think imma do that right now. Is that a good strategy?

I guess so. There are sites that will perform simple frequency attacks for you, I think. It's actually not as simple as you think, playing with brture force substitution.
I wrote a script that would display the frequency of characters from input while testing if a challenge was vulnerable
Code: Select all
#include<stdio.h>
int frequency[127] = {0};
int main()
{
   int in;
   while((in = getc(stdin)) != -1)
   {
      frequency[in] ++;
   }
    int x;
    int y;
    for(y = 500; y >=0; y --)
    {
            for(x = 32;x < 127; x ++)
        {
            if(frequency[x] == y)
                printf("%c -> %d\n", x, frequency[x]);
        }
    }
   return 0;
}

It's relivitely easy to figure out the most common letters but without having a lot of text, there is a fair bit of guess work.
Goatboy wrote:Oh, that's simple. All you need to do is dedicate many years of your life to studying security.

IF you feel like exchanging ASCII arrays, let me know ;)
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Re: What algorithm and key is this message?

Post by ghostheadx2 on Thu May 21, 2015 9:33 pm
([msg=88144]see Re: What algorithm and key is this message?[/msg])

What language is that code you wrote in?
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Re: What algorithm and key is this message?

Post by Turn on Fri May 22, 2015 1:07 pm
([msg=88151]see Re: What algorithm and key is this message?[/msg])

I'm pretty sure that's C syntax.
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<cen> .lua print ('Tsyn 9.47.-u 3 12 5')
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Re: What algorithm and key is this message?

Post by cyberdrain on Mon May 25, 2015 3:06 pm
([msg=88185]see Re: What algorithm and key is this message?[/msg])

Turn wrote:I'm pretty sure that's C syntax.

The function int main() would take an unlimited amount of arguments in C, it should be int main(void). Then again, e.g. C++ doesn't require the return 0; at the end. I'd say it's a valid question by ghostheadx2.
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