How do I quickly encrypt a file with AES?

Question

I want to encrypt a file using AES-256. How can I do that quickly and easily, and how can I - or someone else -decrypt it again?

Answer 1

If you want the encryption to be platform independent, you can use openssl:

• Encryption:

  openssl aes-256-cbc -in attack-plan.txt -out message.enc

• Decryption:

  openssl aes-256-cbc -d -in message.enc -out plain-text.txt

You can get openssl to base64-encode the message by using the -a switch on both encryption and decryption. This way, you can paste the ciphertext in an email message, for example. It'll look like this:

stefano:~$ openssl aes-256-cbc -in attack-plan.txt -a
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
U2FsdGVkX192dXI7yHGs/4Ed+xEC3ejXFINKO6Hufnc=

Note that you have a choice of ciphers and modes of operation. For normal use, I recommend aes 256 in CBC mode. These are the ciphers modes you have available (only counting AES):

aes-128-cbc ← this is okay
aes-128-ecb
aes-192-cbc
aes-192-ecb
aes-256-cbc ← this is recommended
aes-256-ecb

See also:

• http://en.wikipedia.org/wiki/Symmetric-key_algorithm
• http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation

Please note:

OpenSSL will ask you for a password. This is not an encryption key, it is not limited to 32 bytes! If you're going to transfer files with someone else, your shared secret should be very strong. You can use this site to get a sense of how good your password is:

• https://www.grc.com/haystack.htm (this doesn't take into account any dictionary attacks!)
• http://howsecureismypassword.net (this at least check for common passwords)

Answer 2

7z (when the password option is used) uses a 256bit AES encryption (with SHA256 key stretching).

Install it (p7zip-full), right click on a file or directory you want to encrypt, and choose Compress, .7z and Other options /Password.

For decryption, right click on the .7z file and choose Extract here.

Answer 3

aescrypt

The linked website contains an open-source 256-bit aes encrypt/decrypt tool and is multiplatform - MacOs, Windows, Linux and others through Java.

Encrypt: aescrypt -e -p <password_message> <file>

Decrypt: aescrypt -d -p <password_message> <file>

You could backup and encrypt your home folder using the syntax:

tar -cvf - /home/<home_folder> | aescrypt -e -p <password_message> - > backup.tar.aes

ubuntu installation

Download and extract the source

make
sudo make install

other platforms

Download the binaries or source-code from the website.

Answer 4

download Truecrypt, make your own container or encrypt your files. works fine in windows and linux.