There are just too many people and organizations who are interested in our data. Thus, the secure transmission of data is important. Through encryption/decryption, data can be protected from access by third parties. There are already very long easy ways for the encryption/decryption but I have to find again and again that these are quite unknown. Herewith a little tutorial where I want to show possibilities by means of GPG.
Requirements
- Docker (latest)
Environment preparation
By means of two Docker containers, we now want to simulate 2 persons who exchange the encrypted data.
# prepare project $ mkdir -p ~/Projects/GPG-Example && cd ~/Projects/GPG-Example # pull latest centos image (optional) $ docker pull centos # start container (user_a) $ docker run -d -ti --name user_a --mount type=bind,source="$(pwd)",target=/share centos /bin/bash # start container (user_b) $ docker run -d -ti --name user_b --mount type=bind,source="$(pwd)",target=/share centos /bin/bash # check running containers (optional) $ docker ps -a # enter container (user_a eq. terminal 000) $ docker exec -ti user_a /bin/bash # enter container (user_b eq. terminal 001) $ docker exec -ti user_b /bin/bash
Container (user_a)
# show version (optional) $ gpg --version # create a simple text file $ echo -e "Lorem ipsum dolor sit amet,\nconsetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat,\nsed diam voluptua." > /share/example.txt # print file in STDOUT (optional) $ cat /share/example.txt # symmetric encryption $ gpg -c /share/example.txt && rm -f /share/example.txt # check directory (optional) $ ls -la /share/
Container (user_b)
# symmetric decryption $ gpg -d -o /share/example.txt /share/example.txt.gpg && rm -f /share/example.txt.gpg # print file in STDOUT (optional) $ cat /share/example.txt
No passphrase prompt
If you want to use the encryption/decryption without prompt, for example in a bash script, you can use the following options. Depending on the version, it can come to a distinction. Option 1 is by default not available in the Docker containers.
# symmetric encryption (option 1) $ gpg -c --pinentry-mode=loopback --passphrase "PASSWORD" /share/example.txt && rm -f /share/example.txt # symmetric encryption (option 2) $ echo "PASSWORD" | gpg -c --batch --passphrase-fd 0 /share/example.txt && rm -f /share/example.txt # symmetric encryption (option 3) $ gpg -c --batch --passphrase "PASSWORD" /share/example.txt && rm -f /share/example.txt # symmetric decryption (option 1) $ gpg -d --pinentry-mode=loopback --passphrase "PASSWORD" -o /share/example.txt /share/example.txt.gpg && rm -f /share/example.txt.gpg # symmetric decryption (option 2) $ echo "PASSWORD" | gpg -d --batch --passphrase-fd 0 -o /share/example.txt /share/example.txt.gpg && rm -f /share/example.txt.gpg # symmetric decryption (option 3) $ gpg -d --batch --passphrase "PASSWORD" -o /share/example.txt /share/example.txt.gpg && rm -f /share/example.txt.gpg
Multiple files
You can also use a simple loop to encrypt/decrypt multiple files. Please note the available GPG version/options. Here now a simple example without prompt.
# create 3 text files from single file
$ split -l 1 -d /share/example.txt -a 1 --additional-suffix=".txt" /share/demo_
# check directory (optional)
$ ls -la /share/
# start symmetric encryption with multiple file
$ for file in /share/demo_{0..2}.txt; do gpg -c --batch --passphrase "PASSWORD" "$file" && rm -f "$file"; done
# check directory (optional)
$ ls -la /share/
# start symmetric decryption with multiple file
$ for file in /share/demo_{0..2}.txt.gpg; do gpg -d --batch --passphrase "PASSWORD" -o "${file::-4}" "$file" && rm -f "$file"; done
# check directory (optional)
$ ls -la /share/Encryption and Decryption via keys
Container (user_a)
# generate keys $ gpg --gen-key ... kind of key: 1 keysize: 2048 valid: 0 Real name: user_a Email address: user_a@demo.tld ... # list keys (optional) $ gpg --list-keys # export public key $ gpg --armor --export user_a@demo.tld > /share/user_a.asc
Container (user_b)
# generate keys $ gpg --gen-key ... kind of key: 1 keysize: 2048 valid: 0 Real name: user_b Email address: user_b@demo.tld ... # list keys (optional) $ gpg --list-keys # export public key $ gpg --armor --export user_b@demo.tld > /share/user_b.asc
Both public keys are available.
# show folder content (optional) ls -la /share/ ... -rw-r--r-- 1 root root 156 Oct 19 12:19 example.txt -rw-r--r-- 1 root root 1707 Oct 19 13:22 user_a.asc -rw-r--r-- 1 root root 1707 Oct 19 13:27 user_b.asc ...
Both clients need to import the public key from other.
# user_a $ gpg --import /share/user_b.asc # user_b $ gpg --import /share/user_a.asc # list keys (optional) $ gpg --list-keys
Our user_a now encrypt data.
# encryption for recipient $ gpg -e -r user_b /share/example.txt && rm -f /share/example.txt # show folder content (optional) $ ls -la /share/
User_b now decrypt data.
# decryption $ gpg -d -o /share/example.txt /share/example.txt.gpg && rm -f /share/example.txt.gpg # print file in STDOUT (optional) $ cat /share/example.txt
I hope that you have found an entry point into the topic and I have woken up your interest.