# Exchanging session keys over symmetric-key channel?

I know session keys are exchanged (in SSL e.g.) over public-key cryptography channels but I was wondering if there are already known algorithms/methods for exchanging session keys over a symmetric-key channel? More specifically, is it possible/feasible to e.g. exchange 128-bit AES keys over a channel already using 128-bit AES keys?

If so, where can I read about them? IF not, why not? Is it not a good idea or can't be secured?

Possibly related: Deriving Keys for Symmetric Encryption and Authentication

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–  Ricky Demer Jun 24 at 20:34
That might be exactly what I need ... will read it and post back. Thanks! –  mtahmed Jun 24 at 20:37
What I was also asking about was the specific protocols for deriving session keys from symmetric keys ... –  mtahmed Jun 24 at 20:44

"... in plain text", unless the symmetric encryption is forward-secure. $\;$ –  Ricky Demer Jun 25 at 10:38