Re: [Dev-C++] Simple encryption/obfuscation

[David M. <ci...@ya...>]

By definition of your problem anyone who know your algorithm is going
to be able to decrypt the file. Essentially a hacker has all the info
they need if they get their hands on the algorithm and the file that
has both the e-mail and the encrypted data. 

Including a bit of randomness is not going to be easy to do as you
have to somehow rember that random value for you to decrypt it every
time. 

Possibly hide the encrypted data in a file with some other data. And
maybe store the e-mail seperate from the encrypted data. Make it
harder for a hacker to get the data they want, this assumes that a
potential hacker already knows the algorithm.

Hope This Helps
David McKen

--- Ed Cottrell <em...@to...> wrote:
> Hello all,
> 
> I need help on an algorithm. I need to accept username/password
> combinations
> on the client side of a client-server app, store those on the
> client side,
> and "decrypt" them again without user input, using only the stored
> strings.
> Think the "remember my password" function in MS Outlook, IE, etc.
> 
> Ideally, I would like to do this:
> On first run:
> 1) Accept email address
> 2) Accept username & password pairs
> 3) "Encrypt" username/password pairs with email address + some
> machine-dependent data as a key
> 4) Write these encrypted pairs and the email address to a text file
> 
> On future runs:
> 1) Read the encrypted pairs
> 2) "Decrypt" them
> 3) Do stuff.
> 
> The best idea I have now is some block-and-bit chunking and
> shifting - break
> the string to encrypt into variable-length chunks, shuffle,
> reassemble, bit
> rotate, repeat. The "decrypt" would simply reverse the process. My
> concern
> is that anybody who knows the algorithm will be able to reverse it
> quite
> easily, given access to the text file.
> 
> Any help is appreciated!
> 
> -Ed
> 
> 
> 
> 
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=====
Signed 
David Mcken

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