TOPIC: CRYPTOGRAPHIC SOFTWARE
Secure email services: Protecting your digital communications
21st August 2025In an era where digital privacy faces increasing threats from corporate surveillance, government oversight and cyberattacks, traditional email services often fall short of protecting sensitive communications. Major providers frequently scan messages for advertising purposes and store data in ways that leave users vulnerable to breaches and unauthorised access.
The following three email services represent a different approach—one that prioritizes user privacy through robust encryption, transparent practices and a genuine commitment to data protection. Each offers end-to-end encryption that ensures only intended recipients can read messages, while employing various technical and legal safeguards to keep user data secure from third-party access.
From Belgium's court-order requirements to Switzerland's strong privacy laws and Germany's open-source transparency, these services demonstrate how geography, technology and philosophy combine to create truly private communication platforms that put users back in control of their digital correspondence.
This encrypted email service launched in 2013 by ContactOffice Group operates from Brussels, Belgium, providing users with OpenPGP-based end-to-end encryption and digital signature capabilities whilst maintaining servers under Belgian privacy protection laws that require court approval for any access requests. The platform generates private keys within the browser and encrypts them using AES-256 with user passphrases, ensuring the service provider cannot access user encryption keys and supports standard security protocols including SPF, DKIM, DMARC, TLS and two-factor authentication alongside anti-spam filtering. Beyond secure email functionality that works with POP, IMAP, SMTP and Exchange ActiveSync protocols, the service integrates calendar management with CalDAV support, contact organisation with various import and export formats, document storage with online editing through WebDAV access and group collaboration tools for sharing files and calendars.
Founded in 2014 by CERN scientists and now majority-owned by the non-profit Proton Foundation, this Swiss technology company has built a comprehensive suite of privacy-focused services that serve over 100 million users worldwide. The company's flagship service, Proton Mail, offers end-to-end encryption for secure email communication, ensuring that only senders and recipients can read messages whilst the company itself cannot access the content.
The ecosystem has expanded to include Proton VPN for secure internet browsing, Proton Drive for encrypted cloud storage, Proton Calendar for scheduling, Proton Pass as an open-source password manager and recently Lumo, a privacy-centred AI chatbot. All services operate under Swiss privacy laws and employ zero-access encryption technology. The company's mission centres on protecting user privacy against both authoritarian surveillance and big technology companies' data collection practices, offering an alternative to advertisement-supported services that typically monetise user information.
Formerly known as Tutanota, this German-developed encrypted email service operates under a freemium model and was founded by Tutao GmbH in 2011, officially rebranding to Tuta in November 2023. The platform provides automatic end-to-end encryption for emails, subject lines, attachments and calendars using hybrid encryption including AES-256 and RSA-2048, whilst newer accounts benefit from post-quantum cryptography through the TutaCrypt protocol featuring algorithms like X25519 and Kyber-1024.
Registration requires no phone number and the service claims no IP logging, with private and public keys generated locally, and private keys encrypted by user passwords before storage. The open-source platform is accessible via webmail with applications for Android, iOS, Windows, macOS and Linux, and includes an encrypted calendar, contact storage, search functionality and two-factor authentication support. The service has received recognition for its strong encryption and privacy focus but has faced challenges including a significant drop in Google search visibility following Digital Markets Act implementation.
Changing tab titles in the macOS Terminal app using the command line
25th December 2024One thing that I have noticed with the macOS terminal app that I have not seen with its Linux counterparts is that the tab titles can get stuck after an SSH session to a remote server. Thus, I decided to see if they could be changed or reset. Handily, a single command will do just that:
echo -ne "\033]1;New Tab Title\007"
In a UNIX shell (BASH, ZSH, etc.), the echo command outputs text, and it is the text that changes a tab title. Here, the -ne options both negate the generation of a newline (which would be the function of the -n switch if used on its own) and interprets the escape characters included in the text (which would be the function of the -e switch if used on its own).
Within the text string \033 is the octal representation of the escape character that initiates the control sequence that follows it. This is ]1;, the Operating System Sequence (OSC) for setting the tab title in this case, more generally the icon and window title in other circumstances. The text New Tab Title should be self-explanatory, while \007 is the octal representation of the bell character (BEL) that terminates the OSC.
Because I wanted to have the current working directory path as the title, I made a small modification to do this dynamically:
echo -ne "\033]1;$(pwd)\007"
It is the $(pwd) portion that does just that, taking the output of the pwd command and adding it into the string. Thus, I see what is open in each tab. That stopped me ending up in the wrong one, and I even added an alias into the .zshrc file to make it easier to invoke. The functionality may be a more general UNIX or Linux feature, though I have not had opportunity or reason to try it just yet.
What to do when a GPG signature becomes invalid for a package repository on Linux Mint
12th September 2024During a package update on my main Linux system, I encountered the following kind of error message:
An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://cli.github.com/packages stable InRelease: The following signatures were invalid: EXPKEYSIG <GPG Key> GitHub CLI
The message indicated a problem with the GPG signature verification for the GitHub CLI repository. The cause was that the signature for the repository was invalid, preventing the package manager from updating the repository's index files. The first step then was to remove the invalid GPG key using the following command:
sudo apt-key del <GPG Key>
With the invalid GPG key removed, the next step is to add the new GPG key for the GitHub CLI repository by issuing the following command:
curl -fsSL https://cli.github.com/packages/githubcli-archive-keyring.gpg | sudo tee /usr/share/keyrings/githubcli-archive-keyring.gpg > /dev/null
Once I had the new GPG key, I was able to use my usual system update process without any problem. The error message was gone, and updates and upgrades proceeded as intended.
Remedying a warning about an ECDSA host key
25th August 2024During some website maintenance that I have been doing using my iMac, I encountered a message like the following at one point:
Warning: the ECDSA host key for '<server name>' differs from the key for the IP address '<server IP address>'
The cause was a rebuild of one of my web servers and changes to SSH keys that it caused. The solution in my case was to issue a command like the following:
ssh-keygen -R <server IP address>
That felt neater than editing ~/.ssh/known_hosts to remove the affected key. If the command does not remedy things for you, then editing the file should help. That, after all, is what the rest of the warning message suggested to me. My qualms about messing with files made me go with the command, and that got things sorted. There had been some use of ssh-copy-id too, which might be information that is worth having to hand.
Automated entry of SSH passwords
17th February 2022A useful feature for shell scripting is automatic password entry when logging into other servers. This often involves plain text files, which are not secure. Fortunately, I found an alternative. The first step is to use the keygen tool included with SSH. The command is shown below. The -t switch defines the key type, RSA in this example. You can add a passphrase, but I chose not to for convenience. You should evaluate your security requirements before implementing this approach.
ssh-keygen -t rsa
The next step is to use the ssh-copy-id command to generate the keys for a set of login credentials. For this, it is better to use a user account with restricted access to keep as much server security as you can. Otherwise, the process is as simple as executing a command like the following and entering the password at the prompt for doing so.
ssh-copy-id [user ID]@[server address]
Getting this set up has been useful for running a file upload script to keep a web server synchronised, and it is better to have the credentials encrypted rather than kept in a plain text file.