I have at least 15 zip archives, each encrypted with ZipCrypto and a strong password; each containing only "deflate" files (not a single "store" file), compressed with 7zip - compression level 5.
Archives typically contain multiple .xlsx files, sized 5 - 20 kb, and one large .zip file, sized 100 Mb - 4 Gb. I don't have decrypted versions of any of the files in the archives, nor can they be obtained, but I do have .xlsx and .zip files with similar content (.xlsx with identical formatting, column names, etc; .zip files compressed with identical process).
Is there an attack vector that has any realistic chance of success for such situation? Is there a chance that same compression algorithm of similar file would yield usable bytes for attack (is there a predictable result of deflate compression when applied to the large .zip files, or .xlsx files with repetitive elements)?
I have at least 15 zip archives, each encrypted with ZipCrypto and a strong password; each containing only "deflate" files (not a single "store" file), compressed with 7zip - compression level 5.
Archives typically contain multiple .xlsx files, sized 5 - 20 kb, and one large .zip file, sized 100 Mb - 4 Gb. I don't have decrypted versions of any of the files in the archives, nor can they be obtained, but I do have .xlsx and .zip files with similar content (.xlsx with identical formatting, column names, etc; .zip files compressed with identical process).
Is there an attack vector that has any realistic chance of success for such situation? Is there a chance that same compression algorithm of similar file would yield usable bytes for attack (is there a predictable result of deflate compression when applied to the large .zip files, or .xlsx files with repetitive elements)?