Understanding the Pomfort Seal

This article will help you understand the intention and background of the Pomfort Seal.

The Pomfort Seal

The Pomfort Seal complements the widely used and production-proven MHL standard for checksums and can only be produced by Silverstack. During the sealing process, Silverstack creates a seal file (.pfsl) that references all MHL files on the drive. An additional MHL file will be created for all data that was detected on the drive but was not copied onto it with Silverstack. The Pomfort Seal holds all this information together and is even secured against altering the seal itself. Any kind of change of the data on the drive will break the seal and will therefore be detected by Pomfort SealVerify.

Please note that the term of “sealing” has nothing to do with encryption of the data on a drive. The Pomfort Seal does not limit the access to your data. The sealing process aims for integrity, consistency and completeness of data. The term “sealing” is not used in a way that implies a “blocking” or “locking” of data.


Sealed vs Unsealed

The following table will show you the advantages of a drive sealed with Silverstack:

  consistency consistency + completeness
MHL only
(misc. copy tools)
MHL + Pomfort Seal
(Pomfort Silverstack)

MHL files (or other hash files such as .md5 files) basically carry hash values and filenames. With this information, you can verify the consistency of files without access to the original source files. The appropriate tools can determine if the contents of the files mentioned in the MHL file still have the same content as at the time when the hash values have been created. The MHL files are usually created during a copy process.

For a drive with multiple folders copied with multiple copy processes (for examples on a film set, where multiple camera cards are copied to the same travel drive), you cannot verify if one entire folder together with its MHL file is missing. This means with MHL files alone you can verify consistency of single files, but not the completeness of an entire drive.

To solve this problem , the Pomfort Seal contains a list of all MHL files on a drive. With this information, a missing MHL file can detected very easily. This  means that the Pomfort Seal together with the MHL files allows to verify consistency as well as completeness of a travel drive.

The sealing process in Pomfort Silverstack also searches for files on the drive that haven’t been listed in MHL files yet. This ensures, that the Pomfort Seal together with the MHL files cover the entire content of the sealed drive.

Pomfort SealVerify is the free one-button process to verify the Pomfort Seal and the listed MHL files. This way a reliable copy chain can be built where both, consistency and completeness of media data can be verified at any time.