#599 How to Create a Footer for a 7z File Missing Its Tail

[Braden T]

I created a 7z archive, which I no longer have the source files. The 7z was created using 7z, LZMA2, SHA256, AES.

I know the password, but the footer is damaged. Is there a way to generate a new footer with this information? I followed the recovery steps on the 7-zip.org website; however, it does not account for if encryption is involved.

Thank you!

[Igor Pavlov]

you can use same password for new archive.
but first 16 bytes of lzma2 stream will be corrupted after recovering, because first 16 bytes depend from random 16-bytes AES-IV vector stored in footer.

So recovering will be more difficult.
You must write special software that
decodes aes part without lzma2 unpacking.
find new lzma2 chunk and you need recover from that chunk.