mcrypt and public key

jsheehy

Hello,

I've done a couple of searches on the net and a few forums and I've been unable to find a decent answer to my problem. The scenerio is this:

I'm setting up a system where users can send messages to each other. The messages will be stored in an encrypted format so that, if the data is comprimised, no harm is done. However, I need the system to use public key cryptography, because there is no secure medium by which a secret key could be agreed upon.

When I looked into the mcrypt library, I was unable to find any way to use public keys; there seemed to only be private keys.

So how is this done? Surely there is a way...

Thank you.

leatherback

Hi,

if you are using a server-side script, there is no need for public keys, since the data which gets' send is en/decrypted on the server.

jsheehy

So, if I don't use a public key system, how will it work? Person A wants to send a message to Person B. With public key, Person A just uses Person B's public key and sends the message, then Person B decrypts it with his/her private key. Done.

But without using that system, how are two people to communicate securely? Perhaps I'm just dense, but I don't know how I would do that.

laserlight

there is no secure medium by which a secret key could be agreed upon

Then you must use a public key cryptosystem.

When I looked into the mcrypt library, I was unable to find any way to use public keys; there seemed to only be private keys.

At the moment yes - it looks like mcrypt does not yet support public key ciphers.

You could then either implement the support yourself, or more feasibly request your users to use a tool such as gnupg in order to communicate securely.