Charly's Column – Age

Age (think "aghe" in "spaghetti") promises an uncomplicated approach to encrypting and decrypting files. Written in Go, both the source code and precompiled binaries for various platforms can be found on GitHub [1]. I tried Age on a Raspberry Pi, but the tool also runs on Linux on a PC, macOS, and Windows. The author says the current release from mid-June 2021 is "maybe actually the last v1.0.0 release candidate."

Age supports two ways to encrypt and decrypt files. With the first option, you can create a key file (Age calls this an identity file) based on SSH keys with whose contents you then encrypt the data. In contrast to SSH, this is a symmetrical procedure, so the same file is also used for decryption.

As a second option, Age lets you use a passphrase to encrypt the data. This has the advantage that you can think up a new passphrase for each encryption process. A person you trust and give a passphrase to can use it to decrypt your data – but only the data you encrypted with precisely that one passphrase.

Let's look at both methods. By way of an example, I copied the file /etc/passwd to my home directory and will now encrypt it using both methods in turn. For the key file method, I need to generate the key file first – I can do this with age-keygen (Figure 1).

Figure 1: age-keygen handles the task of generating a key file.

The next step is to encrypt the passwd file with the key I just generated (Listing 1, line 2). This creates the encrypted passwd.age file. To decrypt it, use the command from the line 3 of Listing 1.

01 $ age-keygen -o age-key.txt
02 $ age --encrypt -i age-key.text -o passwd.age ./passwd
03 $ age --decrypt -i age-key.text -o passwd passwd.age

Now I'll do the same thing but with the passphrase method. Again, I encrypt the passwd file and give it the name passwd.age. After the corresponding call shown in line 1 of Listing 2, Age asks me for the desired passphrase. If I don't enter one, the tool generates one itself. Decryption works in the same way, but you can leave out the --passphrase parameter here (line 4).

01 $ age --passphrase -o passwd.age passwd
02 Enter passphrase (leave empty to autogenerate a secure one):
03 Using the autogenerated passphrase "release-response-step-brand-wrap-ankle-pair-unusual-sword-train".
04 $ age --decrypt -o passwd passwd.age
05 Enter passphrase:

The entire procedure's security relies, of course, on careful handling of the key or the passphrase.

The Author

Charly Kühnast manages Unix systems in a data center in the Lower Rhine region of Germany. His responsibilities include ensuring the security and availability of firewalls and the DMZ.