http://qs321.pair.com?node_id=910532


in reply to Private Data Communication Protocol Encryption

Okay, I've figured out what was going on there. Sheesh, that was confusing.

First off, the easy (one line!) fix:

$plaintext = substr($input . ("\x00" x $ciphertextsize), 0, $ciphertex +tsize);

The private data communication protocol is designed to send one 64-bit number, not a variable-length string.

That being said, the code above and the web page it links to both have a subtle error in the protocol. Well, "error" is maybe too strong a word - a subtle quirk, maybe? Both the prefilled values on the webpage and the constants in the code look like byte strings encoded in hex.

That is, it's natural to think that $encryptionkey = 'c488fdd0d81f'; defines a six byte encryption key.

It doesn't. It defines a twelve byte encryption key, where all the bytes used happen to be in the range 48-57 or 96-101.

If you're trying to develop perl code to create test AdX RTB responses (that is the point of this, right?), you'll need to do a few things differently:

Hope this helps. I do wish they'd add perl and python implementations to the sample site; it could have saved you some unneeded frustration.

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@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/; map{y/X_/\n /;print}map{pop@$_}@/for@/