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Original author(s)Colin Percival
Developer(s)Colin Percival
Initial release25 April 2008; 11 years ago (2008-04-25)[1]
Stable release
1.0.39 / 29 July 2017; 21 months ago (2017-07-29)
Written inC
Operating systemUnix-like
Size615.7 kB
TypeOnline backup service
As ofJanuary 2016

Tarsnap is a secure online backup service for UNIX-like operating systems, including BSD, Linux, and OS X. It was created in 2008 by Colin Percival. Tarsnap encrypts data, and then stores it on Amazon S3.


The service is designed for efficiency, only uploading and storing data that has directly changed since the last backup.[3] Its security keys are known only to the user.[4]

It was developed and debugged, with input solicited from bug bounty hunters, to try to find vulnerabilities.[5] An inadvertent yet serious nonce-reuse vulnerability was found by this process and fixed in 2011.[6]

The document of the presentation "From bsdtar to tarsnap"[7] by Percival from EuroBSD-Con 2013 contains "all kinds of detail on exactly how the algorithms work, how deduplication is managed ... the innards of how Tarsnap works"[8]

See also[edit]


  1. ^ "Old Tarsnap releases". Tarsnap. 20 August 2015. Retrieved 4 January 2016.
  2. ^ Percival, Colin. "Tarsnap Download Page". Tarsnap. Retrieved 23 November 2017.
  3. ^ Fabbro, Andrew (August 2012). "Tarsnap: Online Backups for the Truly Paranoid". Linux Journal: 104–113. Retrieved August 21, 2012.
  4. ^ Dragani, Rachelle (May 17, 2012). "Dropbox Security System Doesn't Lock Down Files, Says FTC Complaint". E-Commerce Times/Technewsworld.com. Retrieved August 21, 2012.
  5. ^ Pauli, Darren (May 18, 2012). "AusCERT2012: FreeBSD talks amateur bug hunting". SC Magazine. Australia. Retrieved August 21, 2012.
  6. ^ Edge, Jake (January 19, 2011). "Tarsnap advisory provides a few lessons". LWN.net. Retrieved August 21, 2012.
  7. ^ Percival, Colin. "From bsdtar to tarsnap - Building an online backup service" (PDF). www.tarsnap.com. Tarsnap Backup Inc. Retrieved 6 November 2015.
  8. ^ Lucas, Michael W (2015). Tarsnap Mastery - Online Backup for the Truly Paranoid (1st ed.). Grosse Pointe Woods, Michigan: Tilted Windmill Press https://www.tiltedwindmillpress.com/?product=tarsnap-mastery-online-backups-for-the-truly-paranoid. p. 32. ISBN 978-0692400203. Retrieved 6 November 2015. External link in |publisher= (help)

External links[edit]