RAR

Revision as of 18:01, 23 July 2022

RAR (Roshal Archive) is a compressed archive format used by the compression software RAR and WinRAR. It was originally for DOS, but has been widely used on Windows (as WinRAR) and other platforms.

The developers make the decompression code available for use in other programs and allow its distribution, but with a license provision that "You cannot use the unrar source to re-create the RAR compression algorithm, which is proprietary."

Discussion

Format classification

RAR can be considered to be a family of three main file formats:

• The (obsolete) format used by RAR before v1.50
• The format associated with RAR v1.50 through v4.x
• "RAR 5.0" format

Even within one of these classes, there can be significant differences between different RAR versions.

Early history

Most of the earliest releases of RAR appear to be lost. Version 1.34 beta (1993-12-05) seems to be the oldest one known to still exist as of this writing, but there were likely about a dozen earlier releases, starting with v0.1 in 1993-03^[1]. Of those that can be found, the first non-beta release seems to be v1.51 (1994-06-17).

Overview of DOS releases

RAR v2.50 (1999-03-24) was the last one for traditional 16-bit DOS. After that came versions 2.60 through 3.93, which use a 32-bit DOS extender. These versions are sometimes called "RAR32", though their actual name is still "RAR".

File identification

RAR files made by versions prior to v1.50 start with bytes 52 45 7e 5e.

RAR files associated with versions 1.50 through 4.20 start with 7 signature bytes: 52 61 72 21 1a 07 00.

"RAR 5.0" format starts with 8 signature bytes: 52 61 72 21 1a 07 01 00.

Specifications

Before v1.50:

• RAR140DC.EXE (self-extracting RAR archive) → technote.doc

v1.50-4.20:

• wrar420.exe (self-extracting RAR archive) → TechNote.txt

5.0 format:

• RAR 5.0 archive format

Various:

• Forensics Wiki article

Software

• WinRAR website
  • Free UnRAR.dll
  • UnRAR source
• Konvertor
• 7-Zip
• The Unarchiver
• RAR: Various versions, at old-dos.ru
• WinRAR: Various versions, at old-dos.ru
• SAC archive, PACK section - Has lots of RAR software, but no easy way to get a list of it.
• RAR 1.40.2 beta (DOS)
• RAR 1.55 (DOS)
• RAR 2.50 (DOS)
• RAR 3.93 (DOS, OS/2)

Sample files

• http://cd.textfiles.com/ataricompendium/FILES/MISC/PRTFOLIO/
• http://cd.textfiles.com/thebbsorg/max_files/
• https://telparia.com/fileFormatSamples/archive/rar/ → *.rar

Links

• Wikipedia article
• Mini RAR poster
• ReScene's list of RAR versions

References

1. ↑ Discussion at [1]