multiple keys to 1

[rbg9000]

Sorry, I really don't know much about encryption, and my google searches haven't turned up much.  I wondering if it's possible to reduce a set of symmetric keys (aes, twofish, etc..) used to encrypt data into 1 key that can decrypt it?

Something like this
C(k0, C(k1, C(k2, d) ) ) = C(ka, d)
where ka = F(k0, k1, k2)

They probibly design cyphers to keep this from being possible, but the application of this would be useful to me.

Thanks.

[Moderator's note: You are basically asking if these composed
 encryption operations form a group. In general, your surmise that
 conventional ciphers are designed so they do not form a group is
 correct, and you cannot do what you propose. However, what you want
 IS possible in the world of RSA in that you can produce sets of
 encryption keys that correspond to a single decryption key.  --Perry]
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