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I wonder if it would be possible to use a script to share ownership of an UTXO between 2 or more people.

1 <A pubkey 1> <B pubkey 2> N OP_CHECKMULTISIG

That would let every owner be able to spend these coins without needing to ask the other ones for permission.

This is at the moment a valid standard script that is accepted when it is being sent to the Bitcoin network.

But i am asking myself if this could be used to trick people?

If i pay with such a transaction with the receivers public key and my one in the script, i would still be able to spend these coins afterwards. And the receiver would not even notice that i am able to steal back my paid coins. Is this a realistic scenario?

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Generally wallets don't recognize payments to random outputs, even if they're able to spend from them. In situations where multi-signature outputs are used, they're generally part of a scheme that the wallet knows about and participates in (for example 2-of-3 multisignatures where one of the keys is in your phone, one in a vault, and one is held by the wallet provider; usually the provider signs transactions you ask them to, but you can also spend with just the vault key).

This avoids the situation you're describing.

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in your 1-of-2 example, you would have four steps to be followed:

1.) creation of redeem script 
2.) share of redeem script
3.) create a funding transaction with the condition in the redeem script
4.) create a spending transaction with one of the two public keys

at the point where you share the redeem script (2), you would already know (and even see), that there are two keys involved. So wether it is you or your transaction partner, both have the information to see, that there are two possible spending ways: creating a tx with pubkey1 or creating a tx with pubkey2. Not sure how you could trick people with this...

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