Following your comments, I’ve built a new version of my sparse bundle utility Spundle which significantly extends its features.
First, it can now create new sparse bundles that are encrypted. There are three options: no encryption at all, AES-128 and AES-256. These can be used with any of the file systems which it supports, most importantly HFS+ and APFS.
In addition to that, Spundle 1.1 can change the band size in existing sparse bundles, so long as they’re not encrypted. I’m not sure why, but all my efforts to achieve this with encrypted sparse bundles have failed with the same error. However, this feature appears to work fully on unencrypted sparse bundles, and causes them to be written out afresh, which can save space in the bundle.
The third new feature is displaying extensive information about existing sparse bundles.
I had hoped to add a fourth feature in this new version, to enable the password to be changed on a sparse bundle which has already been encrypted. That too has been struck by problems, and will I hope appear in a future revision. I’ve kept a place for the button in Spundle’s window.
All five button commands now have menu equivalents, which also provide them with command key shortcuts. I have tidied up several other loose ends, such as removing the redundant KB maximum size unit, and retitling the buttons.
Thus Spundle now supports the following options when creating a new sparse bundle:
- maximum size from 1 MB to 2 TB,
- band size from 1 MB to 1 TB,
- six file systems – HFS+, journalled HFS+, APFS, exFAT, MS-DOS and UDIF
- no encryption, AES-128 or AES-256.