Re: SMS Encryption

[Pawel Kot]

On Fri, 3 May 2002, Marco Manyevere wrote:

> I'm working on a client/server application that communicates financial
> transactional information using SMS messages. Does anyone know how to
> encrypt/decrypt SMS messages producing only printable ASCII characters but
> without increasing the message size? Alternatively, what I can use is a
> checksum attached to the clear text message that guarantees me that the
> message and the checksum have not been modified in transit. Does anyone have
> some ideas?

Do your messages have the equal length? And how secure do you wish to be?
You can create some codebook and store there keys with a length equal to
the message length for each client. Then just XOR the message with a key.
The client would need to use the next key from the own list to be able to
decode. Old keys cannot be used anymore. The keys should be random.

Just a first thought.

pkot
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