I had a question. Im trying to backup and encrypt files, but using the more recent aes256 or aes512 encryption.
1) I heard 7z defaults to aes128, I want to use the best one (aes256... i think?), how do i do it?
Here is my command:
cd /mnt/MyBackupHardDrive ; 7z a MyFullComputerBackup-AES256.7z -t7z -m0=lzma2:d1024m -mx=9 -aoa -mfb=64 -md=32m -ms=on /home/MyHomeDirectory 2) Does this automatically encrypt the filenames too?
Thanks for any help you can offer!
01 Answer
It is possible to get AES 256 encryption with 7z and make the archive and filenames only visible with the use of a passphrase. I note that the vital 'passphrase' option is missing from your own command line.
An example, for which I have borrowed liberally from the man pages:
7z a \ -t7z -m0=lzma2 -mx=9 -mfb=64 \ -md=32m -ms=on -mhe=on -p'eat_my_shorts' \ archive.7z dir1 A slightly more secure method is to actually leave the -p field blank, then 7z will prompt you to type a password before actually creating the archive.
Explanation:
Here is an explanation for those not well versed in the 7z command line:
a Add (dir1 to archive.7z) -t7z Use a 7z archive -m0=lzma2 Use lzma2 method -mx=9 Use the '9' level of compression = Ultra -mfb=64 Use number of fast bytes for LZMA = 64 -md=32m Use a dictionary size = 32 megabytes -ms=on Solid archive = on -mhe=on 7z format only : enables or disables archive header encryption -p{Password} Add a password Testing the archive:
The subsequent archive can be tested with the command 7z l -slt archive.7z which I demonstrate below:
andrew@illium~/test$ 7z l -slt archive.7z 7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21 p7zip Version 16.02 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on,64 bits,8 CPUs x64) Scanning the drive for archives: 1 file, 12919 bytes (13 KiB) Listing archive: archive.7z Enter password (will not be echoed): <------------- -- Path = archive.7z Type = 7z Physical Size = 12919 Headers Size = 247 Method = LZMA2:14 7zAES Solid = - Blocks = 1 ---------- Path = dir1 Size = 0 Packed Size = 0 Modified = 2017-06-23 14:10:59 Attributes = D_ drwxr-xr-x CRC = Encrypted = - Method = Block = Path = dir1/200px-Aum_calligraphy.svg.png Size = 12663 Packed Size = 12672 Modified = 2015-05-06 07:29:23 Attributes = A_ -rw-r--r-- CRC = 77BD9922 Encrypted = + <------------- Method = LZMA2:14 7zAES:19 <------------- Block = 0 andrew@illium~/test$ Note the call for a password as well as the notation that gives the encryption as 7zAES:19 aka AES-256 (I have arrowed these points for the sake of clarity).
Caveats:
Note that in the man pages there is a specific warning against using 7z for archival purposes under Linux:
DO NOT USE the 7-zip format for backup purpose on Linux/Unix because : - 7-zip does not store the owner/group of the file.Note as well some limitations and work arounds given in the man pages in regards to the backing up of directories under Linux....
