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To: python-list@python.org
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject: Re: Pure Python Data Mangling or Encrypting
Date: Sat, 27 Jun 2015 10:39:13 -0400
Organization: IISS Elusive Unicorn
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On Sat, 27 Jun 2015 13:38:46 +1000, Steven D'Aprano <steve@pearwood.info>
declaimed the following:


>
>Sometimes you say the user is supposed to encrypt the data themselves:
>
>    While the data senders are supposed to encrypt data, that's not
>    guaranteed
>
>
>Now you say that the application encrypts the data, except that the user can
>turn that option off.
>
	<SNIP>
>
>Great to hear it! Just make sure your application always encrypts the
>uploaded files, and you protect both the sender of the files and the
>receiver.
>

	Just an aside: I'm still not clear on just where this application
resides!

	Some posts make it seem like it is all on the storage server, with
nothing running on the sender (a web page file submittal page, for
example).

	If the "application" consists of both client side and server side
programs, with some defined protocol (proprietary to minimize the odds of
someone spoofing as a client) between them, then yes -- just do the AES
encryption in the client before sending... The server never needs to know
the key [the client installation will need a key, preferably generated
locally, and saved so the file can be decrypted later]. If the files will
be retrievable by others than the originator, a public key system (PGP/GPG)
might need to replace the AES encryption.

	For the web-page submittal scheme -- as far as I'm concerned it is too
late to bother encrypting the received file. The only excuse would be that
the server machine itself is insecure and anyone could log-in and peruse
the file system looking at stuff. For this I wouldn't even consider using
the file system to store these snippets... Use a database and store them as
BLOB data, along with suitable information for keying on the content
(submitter ID, submitter filename), make sure the database storage and the
DBMS run as some limited privilege process, and have all access SQL pass
through a limited user account.

-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/