The "session" keys are random strings. They are generated in the source as follows:
UserSession.prototype.generateSessionID_ = function () {
if (window.isDebugMode) {
return "chat";
} else {
var chars = "abcdefghijklmnopqrstuvwxyz0123456789";
var retVal = chars.charAt(Math.floor(Math.random() * 26, 1));
for (var i = 0; i < 10; i++) {
retVal = retVal + chars.charAt(Math.floor(Math.random() * chars.length, 1));
}
return retVal;
}
}
You could also simply use Firebase.push(), which generates random ids that also serve as sequential, chronological record ids:
function generateSessionId(ref) {
return ref.push().name();
}
var fb = new Firebase(URL);
console.log( generateSessionId(fb) );