Calendar Lock PEA - Free Encrypted iCalendar Application

Calendar Lock PEA is an easy to use open source calendar tool that you can use for keeping track of your events. It includes a customizable month, week and day view where you can edit your appointments, as well as a task manager. The calendars can be stored with various cloud providers.

Window for one month with seven columns for weekdays, five rows and colored event buttons Calendar Lock PEA: Month View


Main Features

Privacy Protection

Confidentiality through On-the-fly encryption: The content is decrypted only when requested and only in memory, never on disk.

iCalendar Compatibility

Compatible with iCalendar data (ics files), such as those used in Google Calendar, Apple Calendar, Microsoft Outlook and other areas.

Cloud Support

Save your calendars in the cloud and upload new versions using several cloud providers. All data remain encrypted during this process.

Authenticated Encryption

Protects the integrity of the data by an authenticated encryption. This guarantees that the data has not been manipulated.

Key File

Add a second factor besides the password and protect your data additionally with a key file. Store this key file wherever you want.

Encryption at rest

Separate rarely used data from data in daily use, store them in extra files, and define customized security levels for each type of data.

Additional Features

The program is small and consists of a single archive file. Installation is not required.

Calendar Data and Privacy Issues

Calendar data should always be available and never be lost, which is one reason they are often stored in the cloud.

Dialog displaying a file name to open and a password field Password dialog to open encrypted calendars

At the same time, calendars contain very sensitive and personal information: Appointments allow a precise profile of when you are where, after-work events also reveal something about personal preferences and relationships, medical consultations about your health condition... This is why they are a worthwhile target for snooping:

It is not just about not giving potential burglars information about when you are not at home. The protection of calendar data is also a social responsibility: often, calendar data not only reveals private information about oneself, but also about others. And a world in which big Internet companies, criminals and intelligence agencies have gigantic amounts of information at their disposal is a scary world for almost everyone.

Calendar Applications and Data Collection

The popular calendars have many features: Automatic synchronization between devices, events or whole calendars can be easily shared with others, emails can be sent automatically, restaurant reservations or hotel bookings are automatically inserted...

But these features come at a high price: Many popular calendar apps not only collect users' event data, but also phone numbers, email addresses, location data, photos, videos, contacts and much more.

Google Calendar

With Google Calendar, a lot of additional data is tapped besides calendar data. Under the somewhat deceptive term Data Safety, these are listed in the AppStore. Google claims in their support: Google Calendar uses data to improve your experience. This is certainly only part of the truth. The fact that Google's business model consists primarily of collecting data is not mentioned.

Apple Calendar

Apple advertises a lot with the encryption of data in the new "Advanced Data Protection". However, encryption only creates confidentiality if the key is held by the user. But Apple has the key and thus the protection from Apple itself is zero. Apple's security claims regarding calendar data and contact data are misleading. Read more: Blog post by Ben Wolford.

Microsoft Outlook

The days when Microsoft only stored data locally on the PC are long gone. This also applies to Outlook calendar data. As it also stated in a response to a user query: There is no way to deny Microsoft access to the data. The only positive point is that Microsoft does not suggest privacy, after all.

The data from Google Calendar, Apple Calendar and Outlook, for example, can be protected from others with a little know-how and effort, but it is not possible to protect them from the companies themselves.

The popular application services are convenient, but their use does not reflect a sense of responsibility. Calendar Lock PEA is not the only way to responsibly handle your own data and that of your relatives. If the Calendar Lock PEA does not meet your expectations, take a look at the Alternatives to Calendar Lock PEA.

Encryption: End-to-End, Client-side, Server-side, On-the-Fly

The term end-to-end encryption does not quite fit here, not even for cloud support, since there is only one end, but it is correct that the data can only be accessed at the user end.

Calendar Lock PEA's technique is client-side encryption: the data is encrypted before it leaves the user and is sent to a cloud server, for example. In contrast, Google, Apple and Outlook calendar encryption - if any - is server-side encryption, which means that the companies hold the keys and they decide who has access to the data and what it is used for.

The Calendar Lock PEA also offers a characteristic that is called on-the-fly encryption. This means that the data on the storage medium always remains encrypted and only the requested data in memory is decrypted. This is easier to use and less error-prone. You don't have to continually encrypt and decrypt the data, and even in case of a system crash, the encryption remains intact.

Security Levels

Window for one week with seven columns for weekdays, lines for hours and colored event buttons Calendar Lock PEA: Week View

This application wants to keep the calendar data private. However, greater protection of the data also goes hand in hand with a certain amount of effort. That is why different levels of protection are available:

Lowest Level

If you want the calendar data to be protected only in the cloud and not on your own device, then you can use Calendar Lock PEA like a "normal" application without having to enter the password.
To do this, enable the keyfile-only mode during initialization or later in the settings menu (Security settings - Key derivation function - Use only one keyfile...) and then enable the direct start mode (settings menu - Enable the direct start mode).

Highest Level

The best protection is achieved if you create a key file in addition to the password and store it on a removable medium (USB stick, SD card...).
The effort is then greater, but to what you know (the password) is added something you own (keyfile on a medium) as a second factor.
Additionally, the parameters for the key derivation function can be increased - causing a longer execution time, but also in a higher hurdle for cracking the password.

Between these two extremes, various gradations are possible. The default configuration is to use a password.

Download Options for Calendar Lock PEA 1.7:

Key Derivation Function: Catena-Dragonfly, Argon2
Cipher (EAX-Mode): Threefish, AES-256, Serpent
Hash Function: Blake2b, SHA-3, SHA-512


Thanks to all who have improved, tested or reviewed Calendar Lock PEA and other PEAs

How to use

You have problems to start or use the program? Have a look at the manual.

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