Trying to learn something about obfuscation

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

I'll admit that I am probably getting way ahead of myself, but I have been looking at some of the obfuscation and some of it is just driving me crazy. Would someone please give me some hints as to how the following code could print out JaPh? I understand how it is printing, just do not see where the letters are coming from.

die$;!~y//.-~/c.$;.([$^=~/./g]&~$").$&.($;&{}).$/
[download]

Kerry
"Yet what are all such gaieties to me
Whose thoughts are full of indices and surds?"
quotes the Lama

Comment on Trying to learn something about obfuscation Download Code

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Re: Trying to learn something about obfuscation by gmax (Abbot) on Feb 06, 2003 at 20:19 UTC
In addition to the other explanations, have a look at these nodes, which give some useful tricks about obfuscation and de-obfuscation. Writing highly obfuscated code in Perl Deobfuscation for fun and profit Re: camel code (SPOILERS!) SPOILER! (Guildenstern)Re: How to (ab)use substr Structured obfuscation Yet another structured obfuscation (podmaster: de-obfu) Re: Elusive monks _ _ _ _ (_\|\| \| \|(_\|>< _\|	[reply]
Re: Trying to learn something about obfuscation by rob_au (Abbot) on Feb 06, 2003 at 18:55 UTC
In addition to the direction provided by Mr. Muskrat above, I would also point you to assistance which the perl compiler itself can provide when deciphering obfuscated code. For example, using the `Deparse` backend, a parsed version of the code can be generated which is invariably much more readable: `rob@kathmandu:~$ perl -MO=Deparse -e 'die$;!~y//.-~/c.$;.([$^=~/./g]&~ +$").$&.($;&{}).$/' die !($; =~ tr//.-~/c) . $; . ([$^ =~ /./g] & ~$") . $& . ($; & {}) . +$/; -e syntax OK` [download] Note though that some code can be written to deliberately not be able to be parsed in this manner. The joy of obfuscation. `perl -le 'print+unpack("N",pack("B32","00000000000000000000001000101011"))'`	[reply] [d/l] [select]
Re: Trying to learn something about obfuscation by Mr. Muskrat (Canon) on Feb 06, 2003 at 18:42 UTC
Start by breaking it down. Remember that `y///` is the same as `tr///`. Looking at perlvar we see that `$;` is `$SUBSCRIPT_SEPARATOR`, `$^` is `$FORMAT_TOP_NAME`, `$"` is `$LIST_SEPARATOR`, `$&` is `$MATCH` and `$/` is `$INPUT_RECORD_SEPARATOR`. So what do we have now? `use English; die $SUBSCRIPT_SEPARATOR!~tr//.-~/c.$SUBSCRIPT_SEPARATOR. ([$FORMAT_TOP_NAME=~/./g]&~$LIST_SEPARATOR). $MATCH.($SUBSCRIPT_SEPARATOR&{}).$INPUT_RECORD_SEPARATOR` [download] That should as clear as mud :)	[reply] [d/l] [select]


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