70 votes
Accepted

How do unzip programs check if the password is correct?

Thinking of it as "password protection" slightly misrepresents the actual situation. What happens when you password-protect a zip file is that the archive is encrypted using a symmetric algorithm (...
Shadur-don't-feed-the-AI's user avatar
35 votes

How do unzip programs check if the password is correct?

It depends on the specific zip crypto algorithm. For example, the original ZIP specification used the password to initialize a set of three 32-bit decryption keys. Then the ZIP header (12 random ...
hft's user avatar
  • 5,021
26 votes
Accepted

Crack 7Z password if I also have the original file

7z uses AES-256 with the CBC mode of operation for encryption. Since AES in CBC mode is resistant to known-plaintext attacks ( The CBC mode has greater security than KPA, it has Ind-CPA), having the ...
nobody's user avatar
  • 11.6k
25 votes
Accepted

How is malware distributed within zip files?

Do you remember "I love you" ? Human curiosity often does the trick, unarchiving the zip and then executing the JS (via the windows scripting host that does not follow the same restrictions as a ...
Tobi Nary's user avatar
  • 14.4k
25 votes
Accepted

At which point can a system be compromised when downloading archived data from an untrusted source?

1 should not present any danger as long as the file is just saved somewhere and no attempts to open it with anything are made. If you view it even with a text editor, there's already a small danger of ...
Overmind's user avatar
  • 8,899
24 votes
Accepted

Is it possible to read a text file inside a password-protected zip file without the password?

No. There are two ways of zip encryption, a classic one, which is weaker, and a newer one based on AES. In both cases the password is needed in order to decrypt the contents (i.e. it's not just UI, ...
Ángel's user avatar
  • 18.8k
22 votes

Will password protected files like zip and rar also get affected by Odin ransomware?

Yes. The zip or rar file will be encrypted like all other files so that they are useless for you. The only protection is making backups to another physical storage. This will help independantly of ...
kaidentity's user avatar
  • 2,654
18 votes
Accepted

Is it safe to click on zip or rar file?

A well known trick will be to disguise a PE or Executable program into an another file, a PDF or an archive for example. Since most of people rely on the file's icon or extention, it works pretty ...
Baptiste's user avatar
  • 1,673
18 votes
Accepted

What encryption method is used by the zip program in macOS?

It's using the original PKZIP 2.0 encryption (variously referred to as "traditional" or "legacy" encryption), described in section 6 of the .ZIP file format specification. It's ...
Gordon Davisson's user avatar
15 votes

How is malware distributed within zip files?

The same user who clicks on the ZIP-file to extract the JS-file also clicks the JS-file. This will launch the Windows Script Host to execute the script (it runs both JScript (JS and JSE) and VBScript ...
tlund's user avatar
  • 354
11 votes

Is it possible to read a text file inside a password-protected zip file without the password?

No, nowadays zip files are protected by AES. This will hide all of the plaintext in a way that you can only recover it when you have the key. The only other thing you can see is the size of the ...
Maarten Bodewes's user avatar
11 votes
Accepted

How long should zip encryption password be for it take 10 years to crack?

If you are using ZipCrypto for encryption, then any password length is insecure. You are using the ZipCrypto cipher, rather than the more secure AES. ZipCrypto is extremely weak, as it is based ...
forest's user avatar
  • 66.7k
10 votes

How is malware distributed within zip files?

Windows Script Host is an automation technology that provides scripting abilities. It is language-independent in that it can make use of different Active Scripting language engines. By default, ...
Cristian Dobre's user avatar
9 votes

How to recover a lost zip file password?

Just wanted to add another method using fcrackzip CLI tool. It's in most Linux distro repos such as Ubuntu & Fedora/CentOS. Using it is pretty straightforward: $ fcrackzip -b -c a1:$% -l 1-6 -u ...
slm's user avatar
  • 255
9 votes
Accepted

How to detect zip file encryption algorithm

7Zip archiver (freeware) has an info button that among other useful things tell you the encryption type an archive is using. As a general note, .Zips usually use something called "ZipCrypto Deflatte"...
Overmind's user avatar
  • 8,899
9 votes

Will password protected files like zip and rar also get affected by Odin ransomware?

At the OS level, a file whatever is its content or structure is nothing more than a sequence of bytes. That means that the sequence of bytes can be read, encrypted and written again (in a crypted ...
Serge Ballesta's user avatar
9 votes

Is it possible to read a text file inside a password-protected zip file without the password?

Unfortunately, not really. What you must understand here is that we are not speaking of a file that "is there", access to the original contents is not actively being blocked by the zip software you ...
John Weisz's user avatar
9 votes

How does a zip file detect a correct password?

The Cyclic Redundancy Check (CRC) field is used to determine whether or not the file is decrypted correctly. Quoted from the original ZIP format specification: After the header is decrypted, the ...
Selcuk's user avatar
  • 193
9 votes

At which point can a system be compromised when downloading archived data from an untrusted source?

In theory all of these places could be exploited. I am not going to go into specific exploits available as these change constantly with archive format and moving tech: Initially downloading and saving ...
Vality's user avatar
  • 399
7 votes

Will password protected files like zip and rar also get affected by Odin ransomware?

Think of your zip as a house (with your data inside the house). Your house has a locked door. The ransomware builds a house around your house with its own lock. You cannot get inside your house unless ...
CobaltHex's user avatar
  • 171
7 votes

Is storing an encrypted zip file to an insecure cloud service an admissible way of securing privacy?

Privacy and confidentiality are different things... A Zip file, even encrypted, is still there, and onlookers may observe not only the archive presence, name and size, but also the individual names ...
Thomas Pornin's user avatar
7 votes

Can the content of a password protected zip file be known?

Yes. Aside from the fact that the filenames are unencrypted, the contents of a password-protected Zip file can be recovered if it uses the old, insecure ZipCrypto cipher which uses the insecure, non-...
forest's user avatar
  • 66.7k
6 votes
Accepted

Approaches to cracking an encrypted zip file

A few suggestions: Try building a dictionary based on all strings you can find on the system. Check that the ZIP file really is encrypted, and not just using a dummy header. Make sure the header is ...
guest's user avatar
  • 88
6 votes
Accepted

Can unpacking a .zip file be harmful for Unix-like systems?

Yes, there can be. The main risk with unpacking zips is that it overwrites an executable or config file. For example, if the zip contains a .bashrc and you extract it in your home directory then it ...
Mike Ounsworth's user avatar
6 votes
Accepted

Encryption Using 7z or Zip File

7-zip uses AES-256 for 7z archives, the strongest version of AES. WinZip offers two kinds of encryption: AES encryption (It's good, but windows doesn't support it.) and weak Zip 2.0 (Legacy) ...
Overmind's user avatar
  • 8,899
5 votes

Is it safe to click on zip or rar file?

Yes, there's risk associated with that. If the tool you use to open the archive has vulnerabilities in it, it's possible that parsing a malicious zip or rar file could allow an attacker to exploit ...
David's user avatar
  • 16.1k
5 votes

Reverse Engineering - .zip file decryption if I have similarly encrypted .zip files and I have password to one of them

As I lack 50 reputation to comment and the question is rather simple, I'll answer directly by assuming some details: Assuming ZIP-encryption utilizes a proper encryption algorithm, no. Even if two ...
GxTruth's user avatar
  • 953
5 votes
Accepted

Can the content of a password protected zip file be known?

Potentially, yes. Encrypted zip files protect the data reasonably well (perhaps the equivalent of a cheap lock) but leak meta-data about the files inside the zip. Like a cheap lock, an attacker with ...
Steve Sether's user avatar
  • 21.6k
5 votes
Accepted

Is it feasible to recover a zip file password consisting of about 16 digits?

the password were chosen randomly, by randomly hitting keys TL;DR: Feasible to crack if the archive was protected with ZipCrypto, not feasible if the archive was protected with "WinZip" AES ...
Alexander Fadeev's user avatar
4 votes

CRC-96(ZIP) decryption

While I'm not familiar with CRC-96(ZIP) I'm assuming it is a longer version of CRC-32, but similar in it's function and implementation, so my answer is predicated on that. CRC is essentially a one-...
Daisetsu's user avatar
  • 5,130

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