|Operating system||Windows, macOS, Android, iOS, Windows Phone, Linux|
|Available in||English, French, German, Hungarian, Spanish|
Tresorit is an online cloud storage service based in Switzerland and Hungary that emphasizes enhanced security and data encryption for businesses and individuals. The Business version offers up to 1TB of storage space per user (the Solo version offers 2TB for one user) and extra security features such as DRM, granular access levels and other functions, which Tresorit cites to creating a safer collaborative environment. Tresorit's service is accessible through client desktop software, a web-based application and mobile apps. Currently, the software is available for Windows, macOS, Android, Windows Phone 8, iOS, and Linux. Currently as of 2021, Swiss Post owns a majority stake in the cloud storage service. Tresorit works as an independent entity under Swiss Post.
In August 2015, Wuala (owned by LaCie and Seagate), a pioneer of secure cloud storage, announced it was closing its service after 7 years, and recommended their users to choose Tresorit as their secure cloud alternative.
By the end of 2016, Tresorit launched a beta of the software development kit (SDK) ZeroKit. In January 2017, Apple's SDK project CareKit announced the option for mobile app developers using CareKit to integrate ZeroKit, enabling zero knowledge user authentication and encryption for medical and health apps.
"Tresors" (German for safes) are encrypted counterparts of uploaded directories. Tresors automatically sync with the cloud as files are added or removed from them, similar to Box.com and Dropbox's desktop software. The main difference between Tresorit and its competition is that Tresorit applies AES-256 client-side encryption to files while they are still local and then uploads them to the cloud. The company claims that due to its end-to-end encryption, users can share protected files and folders with others and work together on them, keeping the documents synced and secure in every step of the process. [non-primary source needed]There are additional layers of security, but the core privacy feature of the service is that the encryption key never leaves the user: Using Zero-Knowledge encryption protocols, Tresorit is not in possession of the users’ authentication data, so the content of files cannot be accessed from their servers nor delivered to authorities upon request.
In 2013 and 2014, Tresorit hosted a hacking contest offering $10,000 to anyone who hacked their data encryption methods to gain access to their servers. After some months, the reward was increased to $25,000 and later to $50,000, challenging experts from institutions like Harvard, Stanford or MIT. The contest ran for 468 days and according to the company, nobody was able to break the encryption. 
Tresorit has received a number of nominations and awards. Up-Cloud Rewards named it one of the top 5 Cloud security solutions for 2012. Early 2016, Forbes listed Tresorit's cofounder Istvan Lam among the European "30 under 30". In 2017, Tresorit was listed as finalist in the Cybersecurity Excellence Awards, category Encryption.
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- Tresorit opens its end-to-end encrypted file-sharing service to the public
- Seagate and LaCie spark security concerns by killing off Wuala cloud storage
- Wuala cloud storage to shut down, offers Tresorit as potential new home
- "0_kit by Tresorit: End-to-end Encryption for Your App". Retrieved 11 January 2017.
- "CareKit + ZeroKit: Protect patient data in the cloud". CareKit. Archived from the original on 12 January 2017. Retrieved 11 January 2017.
- Hinchliffe, Emma (11 January 2017). "Apple enhances security options for its CareKit apps". Mashable. Retrieved 11 January 2017.
- Get 50GB of Free, Encrypted Online Storage from Tresorit
- "Cloud Storage Security - Secure Cloud Storage from Tresorit". tresorit.com. Retrieved 9 January 2018.
- Tresorit takes on PRISM-provoked worries with encrypted cloud storage
- "What is Zero-Knowledge Encryption?". 20 May 2016.
- "Here is Tresorit's first transparency report". Tresorit Blog. 14 December 2017. Retrieved 9 January 2018.
- "Secure cloud storage outfit Tresorit posts $10K hacker bounty — Tech News and Analysis". Gigaom.com. 11 April 2013. Retrieved 18 June 2013.
- Hungarian ‘security freaks’: Hack our startup and we’ll give you $25K
- Hackers, Here's a Way To Make An Easy $25k
- Secure cloud firm Tresorit boosts hacker bounty to $25,000
- "Farewell, Wuala! Pioneering secure storage shuts down, recommends Tresorit". 17 August 2015.
- UP Cloud Computing Conference-Start Cloud Awards rankings as of October 17, 2012 Archived 30 June 2016 at the Wayback Machine
- awards | UP 2012 - Cloud Computing Conference 2012
- "Istvan Lam, 28".
- "2017 Cybersecurity Product Awards - Winners and Finalists - Cybersecurity Excellence Awards". cybersecurity-excellence-awards.com. 3 February 2017. Retrieved 16 June 2017.