Coin.Space also implements BIP32 to generate new addresses for peers. The public key that each participant contributes to the wallet is a BIP32 extended public key. As additional public keys are needed for wallet operations (to produce new addresses to receive payments into the wallet, for example) new public keys can be derived from the participants' original extended public keys. Once again, it's important to  stress that each participant keeps their own private keys locally - private keys are not shared - and are used to sign transaction proposals to make payments from the shared wallet.