Changes in WinRAR 5.00 Beta 1:
1. New RAR 5.0 archiving format. You can use “RAR 5.0″ option in
archiving dialog or -ma command line switch to create RAR 5.0 archives.
Older software including older WinRAR versions is not able to decompress
RAR 5.0 archives, so if you plan to send an archive to other people, it
is necessary to take the compatibility issue into consideration. You
can select “RAR” instead of “RAR5″ option in archiving dialog to create
RAR 4.x archives compatible with previous WinRAR versions.
2. Changes in RAR 5.0 compression algorithm:
a) maximum compression dictionary size is increased up to 1 GB in
64 bit WinRAR. 32 bit WinRAR version can use up to 256 MB dictionary
when creating an archive. Both 32 bit and 64 bit versions can unpack
archives with any dictionary size, including 1 GB;
b) default dictionary size for RAR 5.0 is 32 MB, typically
resulting in higher compression ratio and lower speed than RAR 4.x 4 MB.
You can use “Dictionary size” archiving dialog option or -md switch to
change this value;
c) -md switch syntax is modified to support larger dictionary
sizes. Append ‘k’, ‘m’ and ‘g’ modifiers to specify the size in kilo-,
mega- and gigabytes, like -md64m for 64 MB dictionary. If modifiers are
not present, megabytes are assumed, so -md64m is equal to -md64;
d) RAR 5.0 format includes Intel IA-32 executable and delta
compression algorithms, but RAR 4.x text, audio, true color and Itanium
algorithms are not supported. These excluded algorithms are not
efficient for modern data types and hardware configurations;
e) RAR 5.0 decompression can utilize several CPU cores. Though not
to same extent as in compression algorithm, it improves the
decompression speed on large files with poorly compressible data or when
using BLAKE2 checksums.
3. Changes in RAR 5.0 archive format:
a) file times are stored as Coordinated Universal Time (UTC)
instead of former local time, making file exchange among several time
zones more straightforward;
b) file names and archive comments use UTF-8 encoding.
4. RAR 5.0 recovery record is based on Reed-Solomon error correction
codes. If recovery record size is large enough, 5% and more, the new
error correction scheme provides much higher resistance to multiple
damages comparing to RAR 4.x recovery record. Smaller record, such as 1 –
2%, or less random damage type would result in less difference between
4.x and 5.0. For single continuous damage 4.x and 5.0 efficiency is
about the same.
Additionally to usual data erasures, the new recovery record is able
to detect deletions and insertions of much larger size than in previous
RAR versions. Maximum insertion size is several megabytes. Maximum
deletion size depends on the damage type and in some cases can be as
large as the recovery record size.
Still, the best recovery performance and efficiency is achieved if no
deletions and insertions are present, so all data including damaged
sectors preserve their original positions. Thus, if you use some special
software to copy an archive from damaged media, it is better to choose
the mode, when damaged sectors are filled by zeroes or any other data
instead of cutting them out completely from resulting file.
RAR 5.0 recovery record is more resistant to damage of recovery record
itself and can utilize a partially corrupt recovery record data. Note,
though, that “Repair” command does not fix broken blocks in recovery
record. Only file data are corrected. After successfularchive repair,
you may need to create a new recovery record for saved files.
New recovery record is not based on 512 byte sectors anymore and incorporates more complicated data structures. So it is impossible to specify its size in sectors. For RAR 5.0 archives the parameter of -rr[N] switch and rr[N] command is always treated as a percent of archive size regardless of presence of % character. Typically N% recovery record can repair up to N% of continuously damaged data and increases the archive size by only slightly more than N%. Ability to fix multiple damages is proportional to N.
We used “Screaming Fast Galois Field Arithmetic Using Intel SIMD Instructions” paper by James S. Plank, Kevin M. Greenan and Ethan L. Miller to improve Reed-Solomon coding performance. Also we are grateful to Artem Drobanov and Bulat Ziganshin for samples and ideas allowed to make Reed-Solomon coding more efficient.
5. “Test” command verifies validity of RAR 5.0 recovery record.
Recovery record is tested after processing all archived files. If
corrupt archive contains the recovery record, it might be possible to
repair it even if recovery record validity test is failed. “Repair”
command attempts to utilize even a partially damaged recovery record. So
treat the negative recovery record test result as a reason to re-create
the archive if original files are still available, but not as a reason
to avoid “Repair” command.
6. Changes in RAR 5.0 encryption algorithm:
a) encryption algorithm is changed from AES-128 to AES-256 in CBC
mode. Key derivation function is based on PBKDF2 using HMAC-SHA256;
b) special password verification value allows to detect most of
wrong passwords without necessity to unpack the entire file;
c) if archive headers are not encrypted (“Encrypt file names”
option is off), file checksums for encrypted RAR 5.0 files are modified
using a special password dependent algorithm, to make impossible
guessing file contents based on checksums. Do not expect such encrypted
file checksums to match usual CRC32 and BLAKE2 values.
7. RAR 5.0 archives allow to utilize 256 bit length BLAKE2sp hash (
https://blake2.net ) instead of 32 bit CRC32 as a file checksum. Enable
“Use BLAKE2 file checksum” option in “Options” page of archiving dialog
or specify -htb command line switch to use BLAKE2 checksums. While
producing slightly larger archives, BLAKE2 can be used for file contents
identification. If two files have the same BLAKE2 value, it practically
guarantees that file contents is the same. BLAKE2 error detection
property is also stronger than in much shorter CRC32.
8. Features removed:
a) authenticity verification feature did not provide the required level of reliability and was removed;
b) switch -en (do not add “end of archive” block) is not supported
by RAR 5.0 archives, which always have the end of archive block. This
block helps WinRAR to safely skip external data like digital signatures
appended to archive;
c) old style extension based arcname.rNN volume names are not
supported by RAR 5.0 archives, which use only arcname.partN.rar volume
names;
d) file comments are not supported anymore both in RAR 4.x and RAR
5.0 archives. Console RAR ‘cf’ command is removed. It does not affect
the archive comment support, which is present in both versions of
archive format and is not planned for removal.
9. “Set password” command and “Dictionary size” option are moved to “General” page of archiving dialog.
10. You can use “Save symbolic links as links” option on “Advanced”
page of archiving dialog to save and restore NTFS symbolic links and
reparse points as links, so their contents is not archived. Command line
equivalent of this option is -ol switch. Similar option for NTFS hard
links is “Save hard links as links”. Its command line equivalent is -oh
switch. Both options are available only for RAR 5.0 archive format.
11. Added extraction only support for XZ archive format.
12. Changes in recovery volume processing in RAR 5.0 archive format:
a) maximum number of RAR+REV volumes in RAR 5.0 format is 65535 instead of 255;
b) recovery volume operations are faster than in RAR 4.x;
c) additionally to recovery data, RAR 5.0 REV files also store
service information such as checksums of protected RAR files. So they
are slightly larger than RAR volumes which they protect. If you plan to
copy individual RAR and REV files to some removable media, you need to
take it into account and specify RAR volume size by a few kilobytes
smaller than media size.
13. Maximum path length for files in RAR and ZIP archives is increased up to 2048 characters.
14. Command line RAR returns the exit code 11 if it can detect that
user entered a wrong password. This code can be returned only for RAR
5.0 archives. It is impossible to distinguish a wrong password and data
damage for RAR 4.x archives.
15. ‘v’ and ‘l’ commands display archived file names in the end of
line, not in that beginning as before. Also some fields previously
available in ‘l’ and ‘v’ output are now shown only by ‘lt’ and ‘vt’.
‘vt’ and ‘lt’ commands provide the detailed multiline information for
every archived file. ‘vta’ and ‘lta’ also include service headers into
list.
16. Now the default charset for filelists in commands like ‘rar a
arcname @filelist’ is ANSI for both WinRAR and console RAR. In previous
versions it was ANSI for WinRAR and OEM for console RAR. You can use
-scl switch to override this default.
17. Internal WinRAR viewer can detect and display files in UTF-8 and UTF-16 little endian encodings.
18. UTF-16 little endian encoding is used in RAR and WinRAR log file
rar.log, so Unicode file names are stored in the log correctly. WinRAR
automatically truncates the old rar.log file in non-Unicode format to
avoid mixing different encoding in the same log file. In case of console
RAR you need to delete the old rar.log manually, otherwide RAR will
append UTF-16 messages to existing rar.log.
19. Command line ‘r’ (repair) command can include an optional
destpath\ parameter defining the destination folder for repaired
archive: rar r archive.rar destpath\
Size: 1.33 MB