Re: [Fed-Talk] CAC protocol question
Re: [Fed-Talk] CAC protocol question
- Subject: Re: [Fed-Talk] CAC protocol question
- From: "Miller, Timothy J." <email@hidden>
- Date: Fri, 30 Jan 2009 10:25:17 -0500
- Acceptlanguage: en-US
- Thread-topic: [Fed-Talk] CAC protocol question
On 1/25/09 9:37 PM, "Todd Heberlein" <email@hidden> wrote:
> When someone uses CAC to authenticate to a server (say a web server),
> are all the packets encrypted, signed, both, or neither?
SSL/TLS message exchanges are all documented in the TLS RFC. The session
goes encrypted only after the premaster secret is established.
The premaster secret is established one of two ways:
1) Key transport - the client generates a random premaster secret, encrypts
it with the server's public key, and sends it to the server.
2) Key agreement - the client and server exchange certificates *and*
ephemeral public Diffie-Hellman group and public key parameters, signed by
the sender's certificate private key. The client and server use their own
private DH parameters and the other's public DH parameters to derive the
same premaster secret.
After agreeing on a premaster secret through either method, both client and
server apply a key derivation function to arrive at an encryption key
appropriate for the agreed on algorithm. The next message and all following
are encrypted.
People unfamiliar with SSL/TLS get nervous when they see all the unencrypted
session setup messages, but rest assured the cryptosystem *is* secure.
-- Tim
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