Encryption with Public & Private Key

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.NET

Hi:

Although I have programmed fro many years, I have never had the need to use cryptography... until now.

I need to produce a text based file, then encrypt it using our private key and our suppliers public key. This will enable them to ensure the providence of the file and decrypt it with their own private key.

The supplier has sent me their public key which is a RSA 4096/4096 SHA-2 256 key.

I use C# with .NET 3.5 SP1.

Now for the question: How should I go about this task?

I'm not sure how to encrypt a document with public and private keys, also which should I encrypt first: public or private?

What is the easiest way for me to generate my own public/private pair that conforms with the standard mentioned?

All help greatfully accepted!

Regards,
Martin.

BTW, I have already checked out the CodeProject articles, that is why I'm asking specific questions.