ARJ-PROTECT data is error correction data associated with the ARJ-PROTECT feature of the ARJ archive format.
It is typically created using a command like
ARJ a -hk .... File repair is invoked with
ARJ q ....
ARJ-PROTECT first appeared in ARJ 2.55, which puts the data in a companion .XRJ file. At v2.63(?), the feature was changed to instead append the data to the ARJ file.
The feature presumably also exists in all versions of ARJ32, with the format change happening at v3.02.
For documentation, refer to the "ARJ-PROTECT DATA PROTECTION FEATURE" section of the ARJ.DOC/ARJ.TXT file from a suitable version of ARJ.
XRJ appears to be a raw data format, with no way to identify it from its contents.
For an ARJ file containing such data, the 0x08 bit is set in the flags byte at offset 8.
- ARJ and ARJ32 - Refer to ARJ#Software.