RAR檔打不開？WinRAR 能解壓縮也能加密備份

What's new in this version:

- New RAR 5.0 archiving format. You can use -ma command line switch to create RAR 5.0 archives. By default RAR creates archives in 4.x format.

Changes in RAR 5.0 compression algorithm:
- maximum compression dictionary size is increased up to 1 GB in 64 bit RAR. 32 bit RAR 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;
- 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 -md switch to change this value;
- -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;
- 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;
- 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.

Changes in RAR 5.0 archive format:
- file times are stored as Coordinated Universal Time (UTC) instead of former local time, making file exchange among several time zones more straightforward;
- file names and archive comments use UTF-8 encoding.
- 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 successful archive 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.
- "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.

Changes in RAR 5.0 encryption algorithm:
- encryption algorithm is changed from AES-128 to AES-256 in CBC mode. Key derivation function is based on PBKDF2 using HMAC-SHA256;
- special password verification value allows to detect most of wrong passwords without necessity to unpack the entire file;
- 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.
- Switch -htb allows to utilize 256 bit length BLAKE2sp hash instead of 32 bit CRC32 as a file checksum.
- 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.

Features removed:
- 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 RAR to safely skip external data like digital signatures appended to archive;
- 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.
- Switch -oh stores hard links as link instead of file. It is available only for RAR 5.0 archive format.

Changes in recovery volume processing in RAR 5.0 archive format:
- maximum number of RAR+REV volumes in RAR 5.0 format is 65535 instead of 255;
- recovery volume operations are faster than in RAR 4.x;
- 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.
- 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.
- '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.
- UTF-16 little endian encoding is used in RAR log file rar.log, so Unicode file names are stored in the log correctly.
- Command line 'r' (repair) command can include an optional destpath parameter defining the destination folder for repaired archive: rar r archive.rar destpath

Bugs fixed:
- When adding an incompressible file to non-solid RAR archive, Beta 1 could duplicate the first megabyte of archived file, resulting in damaged file.
- "Add to archive..." context menu command could place a created archive to a wrong folder.
- Fixed XZ archive support, which did not work in beta 2.
- "Convert" command did not allow to use compression dictionaries exceeding 4 MB.
- If both encryption password and archive comment were specified when creating RAR archive, archive comment was not added.
- "View as Unicode (UTF-8)" command in internal viewer did not work, so UTF-8 files were displayed correctly only if their encoding was detected by viewer automatically.
- Maximum compression dictionary size when running in Windows XP x86 is reduced to 128 MB. WinRAR cannot allocate enough memory to create archives with 256 MB dictionary in Windows XP x86.
- Corrections in relative path processing, such as "..arcname.rar" name in archiving dialog or "WinRAR foldername" in the command line.
- If archiving operation cannot allocate memory required for compression dictionary, it automatically reduces the dictionary size.
- Decompression algorithm can store the dictionary in several memory blocks. It helps to unpack an archive on systems with high level of memory heap fragmentation, when no single memory block is large enough to fit the entire compression dictionary.
- Previous beta failed to decompress RAR archives contained both encrypted and unencrypted files. Archives containing only encrypted or only unencrypted files were unpacked correctly.
- By default, RAR 5.0 log files produced with -ilog switch use UTF-16 little endian encoding. Now it can be changed with -scg switch, such as -scag for ANSI encoding.
- Fixed a bug in recovery record generation in RAR 5.0 archive format.
- Under certain circumstances previous beta versions could produce wrong recovery record data, inefficient to repair a corrupt archive. Such invalid recovery record can be identified with "Test" command, which issues "Recovery record is corrupt" warning for it.
- When processing a command like: WinRAR.exe a -sfxmymodule.sfx arcname.exe WinRAR ignored the optional parameter of -sfx switch and used
- default.sfx module. Console RAR.exe did not have this bug;
- WinRAR did not create the folder structure necessary to store unpacked hard links. So if folder containing a hard link did not exist yet, hard link extraction failed;
- "rn" command displayed wrong file names for processed files. Files were renamed properly, only the screen output was incorrect;
- When extracting ACE archive, WinRAR could create empty folders contained in such archive in a wrong destination folder.
- solid archive updating was aborted for archives contaning BLAKE2 checksums
- folder tree panel did not allow to go to the archive root folder
- "Reuse existing window" option did not work if first WinRAR copy was browsing an archive and second WinRAR copy attempted to open another archive in another folder
- "Advanced compression parameters" dialog settings format in Registry was incompatible with WinRAR 4.20
- If 7-Zip archive extraction is cancelled, WinRAR deletes the incompletely extracted file. Previous versions did not delete it.