Easy to crack numeric passwd encrypted file.
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Hello,
I encrypted a 7zip file with a numeric password (some number other than the number 1), and I was able to successfully decrypt it on the command line with the password = 1. The complete command line is: 7z.exe x -y -p1 .\Doc2.7z -o.\decrypted -r.
The other encryption parameters are as follows:
Archive format: 7z
Compression level: Normal
Compression Method: LZMA2
Dictionary Size: 16 MB
Word Size: 32
Solid Block size: 2 GB
Number of CPU Threads: 4
Encrypt file names: NO
Encryption method: AES-256
The size of the file is 2.97 MB.
I tried it several more times with different size passwords and got the same result.
Does anyone know why this happening?
Stephen
Show first 40 lines in log:
7z l Doc2.7z > log.txt
and show test.txt
7z t Doc2.7z -p1 > test.txt
log.txt file content:
7-Zip 9.20 Copyright (C) 1999-2010 Igor Pavlov 2010-11-18
Listing archive: Doc2.7z
Type = 7z
Method = LZMA2 7zAES
Solid = -
Blocks = 1
Physical Size = 3122216
Headers Size = 136
Date Time Attr Size Compressed Name
------------- --- -------- -------- ----------------
2012-02-17 04:23:29 ….A 3123859 3122080 Doc2.docx
------------- --- -------- -------- ----------------
3123859 3122080 1 files, 0 folders
test.txt file content:
7-Zip 9.20 Copyright (C) 1999-2010 Igor Pavlov 2010-11-18
Processing archive: Doc2.7z
Testing Doc2.docx Data Error in encrypted file. Wrong password?
Sub items Errors: 1
It seems 7zip creates the file anyway, even if it can't decrypt it.
I thought I had opened the file to check it contents. I guess I didn't
Is there a way to make it not create the file for this situation?
Stephen
Is there a reason for 7zip creating an empty file, if it can't decrypt it?
1) 7-zip extracts file and compares CRC.
It doesn't check password.
2) 7-zip creates file before any check.