In case you are curious about it, jsos was originally meant to be a web based "operating system" where from a hardware perspective one of the types of hard drives available would be the server. Instead of using a block storage like system (which I considered) it's a key value store (direct to the point of what a hard drive actually does for a user). There are 6 key value stores available to the user. skey (secret and private to the user) pkey (available to be read by any other user) ppkey (available to the open internet) Those set the security of the key Then we have get/set (get and set of a string->string) fget/fset ( same but the value is a large file) So ppkeys and pkey have to specify the user when getting. Then the upload app uses the upload predicate to avoid collisions with other apps.