PEAP and certificates

Robbo777

I'm in the middle of using an NPS server to implement NAP on my network, i've just installed a CA on my DC and i plan on using the PEAP with certificates to use as the authentication method that my users are going to use to authenticate themselves.
Regarding PEAP with EAP-MS-CHAP v2 and EAP-TLS, i'm kind of understanding the difference but i dont think i'm quite fully there yet.
My understanding with the MsCHAPv2 one is that the CA does not give out a certificate to the user and only asks the user to trust it along with negotiating the channel then. The TLS version though does give out a certificate on both the server and client and thats how authentication happens. BUT what is the encrypted channel encrypted with? Is it the contents of the certificate? So the TLS connection is encrypted using the public key of the certificate and decrypted using its private key on the server? What is used for encryption, is it AES and where can i specify this?
If not then what are the certificates used for then in regards to all the encryption and keys that are on them? It's just a bit confusing but when i get some clarification on it, it'll click.


Cheers

OctalDump

TLS generally works by using the public/private key pair for authentication and then to establish a session with symmetric encryption. The supported symmetric encryptions are a function of the server (and the client) and not the certificate. The RFC for EAP-TLS seems to mandate 4 (1 must, 3 should) ciphersuites, and AES is one of those (one of the SHOULDs).

My understanding for this kind of arrangement is that the Enterprise CA issues the client certificates, and the Enterprise CA is trusted by the domain, ergo the clients certificates and so the clients themselves will be trusted. This is sufficient authentication - the public key of the CA (published in the CA's certificate) can be used to decrypt what has been encrypted with the private key (the signature on the client certificates).

I think that MS-CHAPv2 in this arrangement still provides for mutual authentication - since the client authenticates the server by the certificate - but the client authentication relies fundamentally on username/password pairs which is weaker than the certificate arrangement. TLS is preferable IF you have the infrastructure to support it. You can step that up again by using smart cards for the client certificate.

Hopefully someone can add/clarify (or correct) what I've said.

Robbo777

I think i understand it a bit more now, the client has the public key from the certificate and the private key is the "signature" or "stamp" on the certificate to validate who they say they're, the public key can then be used from that certificate to decrypt the private key and then see who the certificate belongs to.