Math::XOR problem

kuratkull has asked for the wisdom of the Perl Monks concerning the following question:

Hello, I am trying to solve the problem: http://projecteuler.net/index.php?section=problems&id=59

The task is to decrypt ASCII text using brute force. The password is 3 characters long, all lower caps.

So the code I have here will print out a small portion of the text using brute force of all versions of [a..w][a..w][a..w]. But I am having a problem here:

until ($numcount==24) {
$pass = @list[$count3].@list[$count2].@list[$count1]; #a combination o
+f three letters
$foo = "@s[$numcount]"; #a ASCII character to try to decrypt
$karp = xor_buf($foo,$pass); # put these together using the XOR module
push @lister,$karp;
$numcount++;
}
[download]

The line where I use the XOR module to combine the two strings isn't working. For example, $pass = abc; but the code output doesn't change when the last letter changes, so the output will be the same when $pass=abd or $pass=abx. But if the first or second letter change, the output changes too. I tested and saw that for some reason, the XOR module doesn't read the last letter, only the two first ones, but when I try a simple version only with strings, it works.

NB! The code is using "while" because it worked even less with "foreach" loops(it only read the first letter).

Any help is immencely appreciated :) Thanks.

Output sample:

0M@O@KKHM@ILBHAHIHILABCLANLJKKCLNLANMOHJHNKHHM@BLMAM@BLMHIAKIMHHNKKH -
+- zyy
0M@O@KKHM@ILBHAHIHILABCLANLJKKCLNLANMOHJHNKHHM@BLMAM@BLMHIAKIMHHNKKH -
+- zyz
0MCOCKHHMCIOBHBHJHILBBCLBNOJKHCLMLBNMOHIHMKHKMCBOMBMCBOMKIBKJMKHMKHH -
+- zza
0MCOCKHHMCIOBHBHJHILBBCLBNOJKHCLMLBNMOHIHMKHKMCBOMBMCBOMKIBKJMKHMKHH -
+- zzb
[download]

Full code:

#!/usr/bin/perl

use Math::XOR;

#$outfile = "output.txt";
#open(HANDLE, ">>$outfile");

@list = (a..z);
$count1 = 0;
$count2 = 0;
$count3 = 0;
@s=(79,59,12,2,79,35,8,28,20,2,3,68,8,9,68,45,0,12,9,67,68,4,7,5,23,27
+,1,21,79,85,78,79,85,71,38,10,71,27,12,2,79,6,2,8,13,9);

until ($count3==26) {

until ($count2==26) {

until ($count1==26) {

until ($numcount==40) {
$pass = @list[$count3].@list[$count2].@list[$count1];
$foo = "@s[$numcount]";
$karp = xor_buf($foo, $pass);
push @lister,$karp;
$numcount++;
}
print @lister," -- $pass\n";
@lister = 0;
$numcount=0;
$count1++;
}
$count1=0;
$count2++;
}
$count2=0;
$count3++;
}
[download]

Comment on Math::XOR problem Select or Download Code

Replies are listed 'Best First'.
Re: Math::XOR problem by ikegami (Patriarch) on Apr 07, 2007 at 22:17 UTC
Your link is somewhat broken. It only works if you have an account on that site. I don't know Math::XOR, and I don't really see the need for it when Perl has a string xor operator. `# Assumes ASCII. $string1 = "@@@@@"; $string2 = "ABCDE"; $xored = $string1 ^ $string2; print($xored eq "\x01\x02\x03\x04\x05" ? "ok\n" : "not ok\n");` [download] In practice: (Added) `my $repeats = (length($cipher_text) / length($pass)) + 1; my $pass_stream = substr($pass x $repeats, 0, length($cipher_text)); my $plain_text = $cipher_text ^ $pass_stream;` [download] Also, I'm not sure why you aren't using a foreach loop. `foreach my $c1 ('a'..'z') { foreach my $c2 ('a'..'z') { foreach my $c3 ('a'..'z') { my $pass = $c1 . $c2 . $c3; ... }}}` [download] Finally, `@list[$count1]` should be `$list[$count1]`. Use `$` when you want a scalar (single element). Use `@` when you want a list (multiple elements).	[reply] [d/l] [select]
Re^2: Math::XOR problem by ww (Archbishop) on Apr 08, 2007 at 01:13 UTC
...and speaking (? piling on ?) re ikegami's note re the link, kuratkull: Could you tell us, please, what the dickens "all lower caps" means, because what's echoing through my minds is that "lower (case) CAPITALS" is an oxymoron of the first order. "Small Caps" is a legit (ie, "meaningful") phrase, but isn't relevant in any way to your question (It's a designation for a font style with letters that look like conventional capital - upper case - letters, but are less tall). However, "small caps" is NOT a character-set in the meaning of your question.	[reply]
Re^3: Math::XOR problem by pKai (Priest) on Apr 08, 2007 at 13:01 UTC
The phrase in the problem description was "lower case characters". I don't see the rationale in drolling over a first time poster (assumed non-native in English, judging by his profile) in this way.	[reply]
Re^2: Math::XOR problem by kuratkull (Acolyte) on Apr 07, 2007 at 23:40 UTC
Thank you mate for helping, this helped me a lot and this helped me closer to completing my task :) I implemented your method, and then instantly googled it, so now im familiar with it; I just couldn't find an implemented operator for dealing with XOR, sorry, I new :) PS! I didn't use the foreach loop: `NB! The code is using "while" because it worked even less with "foreach" loops(it only read the first letter).` Thanks! `#!/usr/bin/perl #$outfile = "output.txt"; #open(HANDLE, ">>$outfile"); @s=(79,59,12,2,79,35,8,28,20,2,3,68,8,9,68,45,0,12,9,67,68,4,7,5,23,27 +,1); foreach my $c1 ('a'..'z') { foreach my $c2 ('a'..'z') { foreach my $c3 ('a'..'z') { until ($numcount==27) { $pass = $c1.$c2.$c3; $foo = $s[$numcount]; $string1 = "$foo"; $string2 = "$pass"; $xored = $string1^$string2; $numcount++; push @lister,$xored; } print @lister, " - $foo - $pass\n"; @lister = 0; $numcount=0; } } }` [download]	[reply] [d/l] [select]
Re: Math::XOR problem by jwkrahn (Abbot) on Apr 07, 2007 at 23:32 UTC
This seems to work pretty well: #!/usr/bin/perl use warnings; use strict; my $msg = join '', map chr, ( 79, 59, 12, 2, 79, 35, 8, 28, 20, 2, 3, 68, 8, 9, 68, 45, 0 +, 12, 9, 67, 68, 4, 7, 5, 23, 27, 1, 21, 79, 85, 78, 79, 85, 71, 38, 10, 71, 27, 12, 2, 79, 6 +, 2, 8, 13, 9, 1, 13, 9, 8, 68, 19, 7, 1, 71, 56, 11, 21, 11, 68, 6, 3, 22, 2, 14, 0, 30 +, 79, 1, 31, 6, 23, 19, 10, 0, 73, 79, 44, 2, 79, 19, 6, 28, 68, 16, 6, 16, 15, 79, 35, 8, 11 +, 72, 71, 14, 10, 3, 79, 12, 2, 79, 19, 6, 28, 68, 32, 0, 0, 73, 79, 86, 71, 39, 1, 71, 24, 5 +, 20, 79, 13, 9, 79, 16, 15, 10, 68, 5, 10, 3, 14, 1, 10, 14, 1, 3, 71, 24, 13, 19, 7, 68, 32 +, 0, 0, 73, 79, 87, 71, 39, 1, 71, 12, 22, 2, 14, 16, 2, 11, 68, 2, 25, 1, 21, 22, 16, 15, 6 +, 10, 0, 79, 16, 15, 10, 22, 2, 79, 13, 20, 65, 68, 41, 0, 16, 15, 6, 10, 0, 79, 1, 31, 6, 23 +, 19, 28, 68, 19, 7, 5, 19, 79, 12, 2, 79, 0, 14, 11, 10, 64, 27, 68, 10, 14, 15, 2, 65, 68, 83 +, 79, 40, 14, 9, 1, 71, 6, 16, 20, 10, 8, 1, 79, 19, 6, 28, 68, 14, 1, 68, 15, 6, 9, 75, 79 +, 5, 9, 11, 68, 19, 7, 13, 20, 79, 8, 14, 9, 1, 71, 8, 13, 17, 10, 23, 71, 3, 13, 0, 7, 16 +, 71, 27, 11, 71, 10, 18, 2, 29, 29, 8, 1, 1, 73, 79, 81, 71, 59, 12, 2, 79, 8, 14, 8, 12, 19 +, 79, 23, 15, 6, 10, 2, 28, 68, 19, 7, 22, 8, 26, 3, 15, 79, 16, 15, 10, 68, 3, 14, 22, 12, 1 +, 1, 20, 28, 72, 71, 14, 10, 3, 79, 16, 15, 10, 68, 3, 14, 22, 12, 1, 1, 20, 28, 68, 4, 14, 10 +, 71, 1, 1, 17, 10, 22, 71, 10, 28, 19, 6, 10, 0, 26, 13, 20, 7, 68, 14, 27, 74, 71, 89, 68, 32 +, 0, 0, 71, 28, 1, 9, 27, 68, 45, 0, 12, 9, 79, 16, 15, 10, 68, 37, 14, 20, 19, 6, 23, 19, 79 +, 83, 71, 27, 11, 71, 27, 1, 11, 3, 68, 2, 25, 1, 21, 22, 11, 9, 10, 68, 6, 13, 11, 18, 27, 68 +, 19, 7, 1, 71, 3, 13, 0, 7, 16, 71, 28, 11, 71, 27, 12, 6, 27, 68, 2, 25, 1, 21, 22, 11, 9 +, 10, 68, 10, 6, 3, 15, 27, 68, 5, 10, 8, 14, 10, 18, 2, 79, 6, 2, 12, 5, 18, 28, 1, 71, 0 +, 2, 71, 7, 13, 20, 79, 16, 2, 28, 16, 14, 2, 11, 9, 22, 74, 71, 87, 68, 45, 0, 12, 9, 79, 12 +, 14, 2, 23, 2, 3, 2, 71, 24, 5, 20, 79, 10, 8, 27, 68, 19, 7, 1, 71, 3, 13, 0, 7, 16, 92 +, 79, 12, 2, 79, 19, 6, 28, 68, 8, 1, 8, 30, 79, 5, 71, 24, 13, 19, 1, 1, 20, 28, 68, 19, 0 +, 68, 19, 7, 1, 71, 3, 13, 0, 7, 16, 73, 79, 93, 71, 59, 12, 2, 79, 11, 9, 10, 68, 16, 7, 11 +, 71, 6, 23, 71, 27, 12, 2, 79, 16, 21, 26, 1, 71, 3, 13, 0, 7, 16, 75, 79, 19, 15, 0, 68, 0 +, 6, 18, 2, 28, 68, 11, 6, 3, 15, 27, 68, 19, 0, 68, 2, 25, 1, 21, 22, 11, 9, 10, 72, 71, 24 +, 5, 20, 79, 3, 8, 6, 10, 0, 79, 16, 8, 79, 7, 8, 2, 1, 71, 6, 10, 19, 0, 68, 19, 7, 1 +, 71, 24, 11, 21, 3, 0, 73, 79, 85, 87, 79, 38, 18, 27, 68, 6, 3, 16, 15, 0, 17, 0, 7, 68, 19 +, 7, 1, 71, 24, 11, 21, 3, 0, 71, 24, 5, 20, 79, 9, 6, 11, 1, 71, 27, 12, 21, 0, 17, 0, 7 +, 68, 15, 6, 9, 75, 79, 16, 15, 10, 68, 16, 0, 22, 11, 11, 68, 3, 6, 0, 9, 72, 16, 71, 29, 1 +, 4, 0, 3, 9, 6, 30, 2, 79, 12, 14, 2, 68, 16, 7, 1, 9, 79, 12, 2, 79, 7, 6, 2, 1, 73 +, 79, 85, 86, 79, 33, 17, 10, 10, 71, 6, 10, 71, 7, 13, 20, 79, 11, 16, 1, 68, 11, 14, 10, 3, 79 +, 5, 9, 11, 68, 6, 2, 11, 9, 8, 68, 15, 6, 23, 71, 0, 19, 9, 79, 20, 2, 0, 20, 11, 10, 72 +, 71, 7, 1, 71, 24, 5, 20, 79, 10, 8, 27, 68, 6, 12, 7, 2, 31, 16, 2, 11, 74, 71, 94, 86, 71 +, 45, 17, 19, 79, 16, 8, 79, 5, 11, 3, 68, 16, 7, 11, 71, 13, 1, 11, 6, 1, 17, 10, 0, 71, 7 +, 13, 10, 79, 5, 9, 11, 68, 6, 12, 7, 2, 31, 16, 2, 11, 68, 15, 6, 9, 75, 79, 12, 2, 79, 3 +, 6, 25, 1, 71, 27, 12, 2, 79, 22, 14, 8, 12, 19, 79, 16, 8, 79, 6, 2, 12, 11, 10, 10, 68, 4 +, 7, 13, 11, 11, 22, 2, 1, 68, 8, 9, 68, 32, 0, 0, 73, 79, 85, 84, 79, 48, 15, 10, 29, 71, 14 +, 22, 2, 79, 22, 2, 13, 11, 21, 1, 69, 71, 59, 12, 14, 28, 68, 14, 28, 68, 9, 0, 16, 71, 14, 68 +, 23, 7, 29, 20, 6, 7, 6, 3, 68, 5, 6, 22, 19, 7, 68, 21, 10, 23, 18, 3, 16, 14, 1, 3, 71 +, 9, 22, 8, 2, 68, 15, 26, 9, 6, 1, 68, 23, 14, 23, 20, 6, 11, 9, 79, 11, 21, 79, 20, 11, 14 +, 10, 75, 79, 16, 15, 6, 23, 71, 29, 1, 5, 6, 22, 19, 7, 68, 4, 0, 9, 2, 28, 68, 1, 29, 11 +, 10, 79, 35, 8, 11, 74, 86, 91, 68, 52, 0, 68, 19, 7, 1, 71, 56, 11, 21, 11, 68, 5, 10, 7, 6 +, 2, 1, 71, 7, 17, 10, 14, 10, 71, 14, 10, 3, 79, 8, 14, 25, 1, 3, 79, 12, 2, 29, 1, 71, 0 +, 10, 71, 10, 5, 21, 27, 12, 71, 14, 9, 8, 1, 3, 71, 26, 23, 73, 79, 44, 2, 79, 19, 6, 28, 68 +, 1, 26, 8, 11, 79, 11, 1, 79, 17, 9, 9, 5, 14, 3, 13, 9, 8, 68, 11, 0, 18, 2, 79, 5, 9 +, 11, 68, 1, 14, 13, 19, 7, 2, 18, 3, 10, 2, 28, 23, 73, 79, 37, 9, 11, 68, 16, 10, 68, 15, 14 +, 18, 2, 79, 23, 2, 10, 10, 71, 7, 13, 20, 79, 3, 11, 0, 22, 30, 67, 68, 19, 7, 1, 71, 8, 8 +, 8, 29, 29, 71, 0, 2, 71, 27, 12, 2, 79, 11, 9, 3, 29, 71, 60, 11, 9, 79, 11, 1, 79, 16, 15 +, 10, 68, 33, 14, 16, 15, 10, 22, 73 ); for my $key ( 'aaa' .. 'zzz' ) { my $plain = $msg ^ substr $key x length $msg, 0, length $msg; my @words = split ' ', $plain; # some heuristics to weed out bad plain text next if @words > length( $msg ) / 3 or @words < length( $msg ) / 8 +; next if $plain =~ /[^[:print:]]/; next if grep( /\b\W+\b/, @words ) > @words / 10; print "Key: $key\n$plain\n\n"; } __END__ [download]	[reply] [d/l]
Re^2: Math::XOR problem by pKai (Priest) on Apr 08, 2007 at 09:39 UTC
TIMTOWTDI: `my $msg = pack('C'.@s, @s);` [download] Or even `'C*'` as template.	[reply] [d/l] [select]
Re^2: Math::XOR problem by kuratkull (Acolyte) on Apr 09, 2007 at 14:36 UTC
:D Thanks mate, this is wonderful; though I will keep digging through my own crappy code to see what i did differently and incorrectly. Thank you again!	[reply]


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