Originally Posted by bakakaka
I believe the ".ab" format is in some kind of "tar" compressed archive.
Doesn't look like it. At least it's neither plain tar nor one of tarred gzip, bzip2 or compress. Also, it's not zip or rar.
So what's left?
- The android backup supports encryption. This does not necessarily mean that the archiver has to support that, too, since you could always first archive and then encrypt or vice versa.
- You can include .apk-files in backups. This suggests, that the archiver does not need to be über-effective, like bzip2, since that would cost time and cycles and .apk-files are already compressed, IIRC.
I don't know how to make any sense of this but maybe someone else does?