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Encrypted File Backups

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CrococryptMirror is a free software without registration, without activation, without limitations and without ads.


Encrypted File and Folder Backups

CrococryptMirror (aka "Crococrypt") is an encryption tool which mirrors complete folders to encrypted folders. The encryption algorithms that are used are AES and Twofish (256 bits, cascading). The keyfile is secured by a password using PKCS #5 (PBKDF2) with a SHA512/Whirlpool based HMAC using 100000 iterations and also AES and Twofish.

Additionally, a ZIP compression for storage space optimization is used. For reasons of performance the synchronization of source and destination folder is done in the background.

A backup copy of the keyfiles has to be stored at a secure place. Without the keyfile the containers cannot be decrypted.

In the portable version of CrococryptMirror keyfile and settings are stored together with the application folder. Hence, the complete application can be transported on an external storage device. Moreover, the folder "container" can be used to store portable containers.

Mirroring can be done manually (on-demand) or by using the sync service which detects directory changes on the fly.


Use Cases

Some use case and feature examples:

Encrypted Cloud backup

Mirroring of folders on your computer into your cloud storage folder in encrypted form.

Encrypted backup on USB drive

Mirroring of folders on your computer to an external storage device in encrypted form.

Encrypted multi-backup

Multiple storage locations can be used in parallel, e.g., an USB drive, Cloud storage and a local NAS. When using the sync service all encryption destinations while be queued and processed sequentially.

Two encryption modes

Use the automatic sync service or mirror a directory on-demand simply by clicking on CrococryptMirror's tray icon. Use the latter if you work constantly on a certain directory and do not want to create to much load for a backup.

Synchronizing means that also deleted files will be deleted in the container's destination, at the end both directories have the same content. The source directory is not touched.

Two decryption modes

A complete directory can be efficiently decrypted in a bulk operation. When only single files shall be restored, the Explorer view can be used. For this purpose, a local WebDav view on the encrypted container is opened (read-only), so files can be browsed and copied.

Technical Background

For technology enthusiasts, we want to describe some implementation details. CrococryptMirror uses two well-known cryptography providers: Oracle (originally Sun) for AES and Bouncy Castle (open source) for Twofish. These are popular implementations, the cryptography is done using these providers not by implementing the algorithms myself. On computers with CPUs which include AES hardware support, this AES implementation is used automatically. This is also done by other popular encryption tools today.

By using two different encryption algorithms and different implementations, the risk of compromising the whole encryption scheme is minimized. For instance, if you store an archive of your personal data in a cloud storage for a very long time, it might happen that weaknesses in the algorithms itself come up or that security vulnerabilities in the implementations are discovered.

The iteration count of 100000 used for the password protection of the keyfile is upwards compatible with future versions and is not hard coded, for maximum flexibility.

Pro Version

To finance the freeware project, we have introduced a Pro version of CrococryptMirror for a small fee. New features of CrococryptMirror will always be introduced in the Pro version first.


These are simply feature ideas, there is no implementation schedule for the freeware version. Nevertheless, we like to hear your suggestions and are happy about your support.

Idea backlog


If you like CrococryptMirror, it would be a great thing if you share it with others to support its further development!

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