MRNZ

File Format
Name	MRNZ
Ontology	Electronic File Formats Archiving MRNZ
Extension(s)	.??_
Released	1994?

MRNZ (for lack of a better name) is a simple installer-archive format. It is a lightly obfuscated non-compressed single-file format. Its only known use is in certain distributions of IBM PC DOS 6.3, where it seems to be a companion to KWAJ format.

Format details

A file seems to be decoded as follows: Skip the first 12 bytes, xor the next 38 bytes with 0xAE, and copy the rest of the file unchanged.

Identification

Files start with ASCII "MRNZ", apparently always followed by 0x88 0xf0 0x27 0x33. The next four bytes always seem to be 0x26 0x00 0x00 0x00, but if this is the number of obfuscated bytes, it might be different for very small files.

Sample files

(Files here are likely in LoadDskF/SaveDskF disk images.)

• Shareware Overload Trio Volume 2 → DIR41/USD631.*, ...
• IBM Presents OS/2 Software Hits - First Edition 1994 → os2_94/I20/{FRD631.*, ..., GRD631.*, ...}