Random decomposition of symmetric key

Considering a symmetric cipher (i.e : AES in counter mode), is it possible for any given key to be randomly decomposed into other keys without knowing the message or the ciphertext, such as :

100 = 45+55 (or) 30+70 (or) 25*4 (or)...

Key1 = Key2|Key3 (or) Key4|Key5 (or)...


For any message, applying Key1 or Key2|Key3 would have the same encryption/decryption result.

One-time pad would be an option but it is not very practical because it would take the same length as the message. I am open to all suggestion. Thanks !

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What do you actually want to do? Split an existing key (for existing ciphertext) to two parties so both are needed for decryption (one after another)? – Paŭlo Ebermann Aug 7 '12 at 17:11
Does the description for the secret-sharing tag sound like what you are trying to do? – David Cary Aug 14 '12 at 0:15