Yes. You can keep one for yourself and one to whomever you want.
* Don't send your private key to someone you don't trust.
P.S. Main point in ChipMixer's post in Reddit is timelock [1] transaction, not multisig.
[1]
https://en.bitcoin.it/wiki/TimelockGreat explanation.
Basically, the proof section of the Chipmixer site is its main provably fair mechanism, since it publishes private keys every single day to prove that bets aren't rigged. What you can do is create a multisig wallet with one of your own private keys and the other as Chipmixer's private key, and voila, your coins aren't technically yours anymore.
So you must be careful in choosing whom to add as a cosigner and not to create a 2-of-2 multisig address with a party who could potentially not sign your transaction. Otherwise, you will loose your coins send to that address. For example, you used 2-of-2 multisig when trading and you had an argument with the buyer/seller, he could decide not to sign transaction and you will loose your Bitcoin. Vice versa, you can do the same too! For trading, it's better to include one or more trusted third party depending on the trade as a cosigner, creating a 2-of-3 multisig address or m-of-n multisig address, n>=3 & m
I have a question - if your coins are in multisig at the time of a hard fork, what will happen to your funds?
Multisig addresses are no different than normal address when it comes to transaction other than 2 or more signatures are required to send Bitcoin in it. Therefore, if there is a hardfork, you can broadcast your transaction into both chains or you can use a client which supports the chain you want. Usually, wallets choose a chain which is technically better/correct or widely accepted.
There is no "coins" in blockchain, only outputs. When a hardfork happens, blockchain will be split into. A chain on top of the blockchain without new rules and a blockchain with new rules. Outputs after hardfork in a chain will be invalid in the other blockchain. When choosing a chain, you must be careful not to chose a chain which nobody or very few people use because you can not broadcast a transaction which includes an output in a blockchain, to other chain.
If you don't understand, consider the current blockchain as a "path", say main_path. What happens when hardforking is, like the path being split into two different paths, say path 1(chain 1) & path 2(chain 2). You can choose which one to walk on -- choose chain.
- Now, consider you are walking on main_path and you or someone stored something, say money, in a place along the way -- a transaction in current blockchain.
- You go on main_path and at the end, you are met with two paths, path 1 & path 2 -- hardfork
- You choose path 1 -- chain 1.
- You or someone else deposited money in a place on path 1 -- sending/receiving transaction in chain 1
- Let's say, after sometime, you want to take all the money you stored along the way. -- sending output
- Regardless of the path(path 1 & path 2) you want to walk to, you *will* have to go through main_path -- current blockchain.
- You can take money deposited in main_path regardless of which path you want to go *to* because to get to path 1 or path 2, you have to go through main_path -- using output in main chain in a transaction and broadcasting it to either of the chains - chain 1 & chain 2.
Now, consider these questions:
Q) Will you be able to get your deposit(output) in path 1(chain 1), if you go through path 2(chain 2)?
A) No.
Q) Doesn't that mean that if you send Bitcoin in chain 1, then that transaction won't be shown in chain 2?
A) Yes.
Q) If so, doesn't that mean we can spend double-spend?
A) Yes. But do note that, outputs in only *one* chain will be valuable.
Q) But, how do I know which chain to follow?
A) You can follow a chain which is followed by most.
Q) I followed a chain and there were many who used that blockchain. My transactions are all in blocks belonging to that chain. What do I do if no one uses that chain anymore? Can I recover my Bitcoin?
A) Your Bitcoin in main_chain will be there in the other blockchain even if you have already used it in the "wrong" chain. All the Bitcoin you received after hardfork, that is, when you used "wrong" chain, will be lost. You have to tell senders to resend Bitcoin to new address and this time, broadcast transaction to the "current/accepted" chain.
Did I miss anything or can't you understand someting? Feel free to ask in *another thread*.
Don't understand you understand anything at all? Ask your questions/doubts in a new thread and someone will answer you.
* Word "output" here refers to UTXO(unspent transaction output).
Is there any way that Chipmixer can offer this service trustlessly as well, for example with nlocktime?
I am not sure how ChipMixer does it. But, there is already a wallet which use nLocktime. You may have heard about it. It is called GreenAddress.
https://greenaddress.it/