Unless you're truly skilled and have a background in cryptology you really shouldn't roll your own cryptography for anything of importance. Encryption is tough to get right without leaking information or being susceptible to a multitude of attacks beyond brute force.
Encryption to me is like a real "Fire Safe", it is only safe for a certain temperature and time but eventually it will get hot inside.
Cryptography has been only a hobby for me for many years, not a profession.
But I have tried to crack some protected RAR files with no success, as long as the passphrase is long and complicated enough. Well, if a government powered brute force is used, I have no idea how long they would need on a RAR file?
I don't know anything about 'TAR-balls' etc, as everything I know about a 'Mac' I could write on the back of a matchbox !!
'ZIP' files/handling is now 'built-in' to Windows, almost too MUCH so !!!.... It shows 'contents' of a Zip as though you are looking
at a normal Windows Folder/Tree/File/View... (Try telling my 'missus' she is looking inside a Zip !!!
).
Encryption types obviously vary, between applications. There WAS a back-door that COULD be exploited for certain OLDER '.Rar'
files, that allowed cracking software to get under the hood & extract. However, that has now been corrected, and will NOT work
now unless you are working with an 'old' .rar compression/encryption.
.RAR files are TODAY, almost synonymous with 'pirating' sites, to simply "go against the 'man'", ie .Zip files !!! Simple as that.
I too have, (just for fun!), 'played' with every legal/illegal Tool known to humankind, to 'crack' certain encryptions, that go
way past the usual boring 'dictionary' attacks, (and I have Giga Bytes of Dictionaries/phrases beyond common thought!).
ALL need many computers taking many weeks or months for anything but the simplest of 'passwords'. (Obviously!).
However, there is ONE 'approach' that works every time for me, in a matter of 5 or 10 mins !!!!!!!....
.RAR (and all other types), of files TYPICALLY contain MANY files... (although not always). And OFTEN... (let's say Pirates!),
have at least ONE 'file' that is often/always repeated, in inclusion with what ever else. This can take many forms, from a
200/500 byte 'speil' about their main site, and/or logos, or a common 'Thanks' to who ever.....
NOW, as long as you have an un-encrypted COPY of ONE of those common files, you are home & hosed.....
Because you NOW have something to COMPARE, the software I use will analyze the encrypted .RAR, against a KNOWN filename
and content, and will quickly find a 'KEY' to the encryption. This is NOT the 'password', but is a KEY that will allow, during
the 2nd pass, to re-write the original .Rar file but without ANY encryption.... 5-10 mins max