• An interface to the zxcrypt driver, as bound to a single block device with a zxcrypt superblock. zxcrypt devices are encrypted, and before their plaintext contents can be accessed, they must be unsealed with a key. This protocol allows the caller to make requests to unseal the device (by providing the appropriate key) and to seal the device (rendering its contents inaccessible).


  • We require simple layout to use the simple C bindings, and simple layout requires that we have non-maximal length bounds, so give some excessively large key length here so we can use the simple layout.