A typical transaction involves two zones: one facilitating the transaction on behalf of the sender, and the other on behalf of the recipient. It is possible for this to be the same zone, though this will not be the case in general. In the course of the transaction, the sending zone validates the transaction signed by the sending user, and if it is deemed valid (signatures are valid, assets are available, channel state and nonce check out), then it also signs the transaction. This vouches for the transaction before the recipient zone. Later, the recipient's zone also validates the transaction, making sure a trusted zone signature is present, and also signs it if valid. This vouches for the transaction before the recipient. In Light Mode, these three signatures (client's, sender zone's, and recipient zone's) are required for a transaction to complete. In Watchtower mode, the transaction also has to be validated and signed by an agent acting on behalf of the recipient, their watchtower, which is free to impose additional validity requirements on the transaction, such as it being part of a sale somewhere waiting for a payment.