Question

I understand better some concepts when I write toy programs for isolated aspects of the problem at hand. For instance, for encryption you can write a program to encrypt and then decrypt a string.. and see that you get the initial string.

What toy programs do you suggest that I write to understand certificates? (server/client interaction, ssl communication, signatures, etc) And/or what .NET namespaces should I explore?

(not important for the question, but I use c#)

Answer 1

• Create a symmetric key and encrypt/decrypt something with it. Modify the encrypted byte [] and try to decrypt it. Play with different padding and modes and repeat a few times.
• Create/Save/Load certificates and private keys.
• Verify the certificate chain for any certificate you find to see the most common kind of errors.
• Create a symmetric key, encrypt it with the public key of one cert (“client”) and the private of another (“server”).
• Create a message that sends the above key encrypted with the “server” private key, then some encrypted text and sign the whole thing. Then decode and verify this using the “server” public key and the “client” private key.

Namespaces?

• System.Security.Cryptography
• System.Security.Cryptography.Authentication
• System.Security.Cryptography.X509Certificates

A few interesting types:

• RSACryptoServiceProvider
• SymmetricAlgorithm
• RijndaelManaged
• ICryptoTransform
• X509Chain