encryption/decryption help

[drs]

Hi, I need to send secure data over an insecure network. To that end, I am
needing to encrypt serialized data and then decrypt it. Is there a builtin
way to do this in Python? MD5, SHA, etc encrypt, but I am not seeing a way
to get back my data. Encryption is totally new to me, so any pointers of
what to read up on would be appreciated.

As a side note, I understand that I could use https, but this would involve
changing things that I may not be at liberty to change -- though if this
turns out to be the best solution, then I'll find a way to use it.

Thanks

[Paul Rubin]

Re: encryption/decryption help

"drs" <drs@remove-to-send-mail-ecpsoftware.com > writes:[color=blue]
> Hi, I need to send secure data over an insecure network. To that end, I am
> needing to encrypt serialized data and then decrypt it. Is there a builtin
> way to do this in Python? MD5, SHA, etc encrypt, but I am not seeing a way
> to get back my data.[/color]

No, Python doesn't include any reversible encryption functions, because
of regulatory obstacles in some countries. Here's a function based
on SHA:

http://www.nightsong.com/phr/crypto/p3.py

It's not ideal and it's nonstandard, but it's written in pure Python
and still has reasonable performance and should have ok security.

It works on 32-bit processors but a simple fix is needed to make it
work on 64-bit processors. I'll put that in when I get a chance.
[color=blue]
> Encryption is totally new to me, so any pointers of what to read up
> on would be appreciated.[/color]

Rule #1 is that there are a lot of subtle mistakes that can kill you.
Try to use standard solutions when you can, instead of doing anything ad-hoc.

The standard reference about crypto implementation is "Applied
Cryptography" by Bruce Schneier. That's got all kinds of stuff about
algorithms and protocols. You could also look at "Practical
Cryptography" by Bruce Schneier and Niels Ferguson. That is more
about what kinds of precautions you should take when implementing
crypto. I disagree with some of what it says, but it's a start.

Also, anyone implementing any type of security system (crypto or not)
should read "Security Engineering" by Ross Anderson.
[color=blue]
> As a side note, I understand that I could use https, but this would involve
> changing things that I may not be at liberty to change -- though if this
> turns out to be the best solution, then I'll find a way to use it.[/color]

Using https is almost certainly a better solution than rolling up
something yourself. Do it if the option is available to you.

[Kartic]

Re: encryption/decryption help

Hi,

Can you use ssh tunneling? You will not be changing anything except add
an extra ssh layer to tunnel your data through. There is how-to at

http://www.ccs.neu.edu/groups/systems/howto/howto-sshtunnel.html

(or you can google for tunneling)

Please note you can not use MD5 as it is not reversible.
Thanks,
--Kartic

[Daniel Bowett]

Re: encryption/decryption help

MD5 and SHA are by their very nature one way encryption. You cannot
decrypt them.

A quick google for other encrytion methods found this:

http://www.amk.ca/python/code/crypto.html

What you will need to do is find an encryption methos that uses a key
which you use to encrypt and decrypt the data.

You could get hold of something like GPG which has a command line
interface and encrypt and decrypt that way....

drs wrote:
[color=blue]
>Hi, I need to send secure data over an insecure network. To that end, I am
>needing to encrypt serialized data and then decrypt it. Is there a builtin
>way to do this in Python? MD5, SHA, etc encrypt, but I am not seeing a way
>to get back my data. Encryption is totally new to me, so any pointers of
>what to read up on would be appreciated.
>
>As a side note, I understand that I could use https, but this would involve
>changing things that I may not be at liberty to change -- though if this
>turns out to be the best solution, then I'll find a way to use it.
>
>Thanks
>
>
>
>[/color]

[Jorgen Grahn]

Re: encryption/decryption help

On 12 Jan 2005 12:39:05 -0800, Kartic <kartic.krishna murthy@gmail.co m> wrote:[color=blue]
> Hi,
>
> Can you use ssh tunneling? You will not be changing anything except add
> an extra ssh layer to tunnel your data through.[/color]

Or, rather, he wouldn't be changing anything at all in the program itself.
The approach would be "Ok, so this protocol is insecure. If you want to
protect yourself from eavesdropping and man-in-the-middle attacks along the
ways, you have to feed it through an ssh tunnel or something similar".

But we don't really know what this person wants to accomplish, so this may
or may not be a viable option.

/Jorgen

--
// Jorgen Grahn <jgrahn@ Ph'nglui mglw'nafh Cthulhu
\X/ algonet.se> R'lyeh wgah'nagl fhtagn!