Tarsnap

{{Infobox software

| name = Tarsnap

| title = Tarsnap

| logo = Tarsnap-logo.png

| logo caption =

| logo size = 260px

| logo alt =

| screenshot =

| caption =

| screenshot size =

| screenshot alt =

| collapsible =

| author = Colin Percival

| developer = Colin Percival

| released = {{Start date and age|2008|04|25|df=yes}}{{cite web |url=https://www.tarsnap.com/download-old.html |title=Old Tarsnap releases |author= |date=20 August 2015 |website=Tarsnap |publisher= |access-date=4 January 2016 |quote=}}

| discontinued =

| latest release version = 1.0.40{{cite web |url=https://github.com/Tarsnap/tarsnap/releases/tag/1.0.40 |url-status=live |lang=en |title=Release 1.0.40 · Tarsnap/tarsnap |website=GitHub |access-date=13 Feb 2022 |archive-url=https://web.archive.org/web/20220213143919/https://github.com/Tarsnap/tarsnap/releases/tag/1.0.40 |archive-date=13 Feb 2022}}

| latest release date = {{Start date and age|2022|02|10|df=yes}}

| latest preview version =

| latest preview date =

| programming language = C

| operating system = Unix-like

| platform = Cross-platform{{cite web|last1=Percival|first1=Colin|title=Tarsnap Download Page|url=https://www.tarsnap.com/download.html|website=Tarsnap|accessdate=23 November 2017}}

| size = 615.7 kB

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| genre = Online backup service

| license = Proprietary

| website = {{URL|//www.tarsnap.com}}

| standard =

| AsOf = January 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.

Service

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

It was developed and debugged, with input solicited from bug bounty hunters, to try to find vulnerabilities. A serious nonce-reuse vulnerability was found by this process and fixed in 2011.

The document of the presentation "From bsdtar to tarsnap"{{cite web|last1=Percival|first1=Colin|title=From bsdtar to tarsnap - Building an online backup service|url=https://www.tarsnap.com/download/EuroBSDCon13.pdf|website=www.tarsnap.com|publisher=Tarsnap Backup Inc.|accessdate=6 November 2015}} 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"{{cite book|last1=Lucas|first1=Michael W|title=Tarsnap Mastery - Online Backup for the Truly Paranoid|date=2015|publisher=Tilted Windmill Pressd|location=Grosse Pointe Woods, Michigan|isbn=978-0692400203|page=32|edition=1st}}