See Commit Methods.
In this commit method, the recipient generates a secret commit token, and then passes it back through the chain of intermediaries to the payer. This method is *not* atomic, however, since it is possible for participants to cheat and not get caught.
The bare commit method is a special case of the registry commit method, and takes that as a starting point. The difference is that the participants do not indicate ahead of time that they trust the registry used. The recipient can choose whatever registry it wants, including acting as the registry itself, or, if it is lazy, specifying the null registry:
urn:ripple:registry:null
This commit method is called bare.
The trusted registry list from the registry commit method is ignored, except for the max deadline length.
The fact of the registry not being known or trusted, or even existing necessarily, leaves this commit method vulnerable to communication outages and cheating. If there is an issue passing the commit message back along the intermediaries, during which time the still-outstanding Promises expire, the transaction may be left half-committed without a trusted authority to remedy the situation.
An unscrupulous hub could, among other things, pretend not to receive the commit message when it arrives in order to profit, either by passing it further down, or by being the payer and recipient in a circular payment. It could then blame the other hub's server for the communication outage, and claim it cannot accept a late commit because of other hubs further down the chain (whether or not they even exist).
The bare commit method requires voluntary cooperation from all hubs in order to work reliably: