Tarsnap - Online backups for the truly paranoid

Tarsnap is a secure, efficient online backup service:

Encryption: your data can only be accessed with your personal keys.
We can't access your data even if we wanted to!
Source code: the client code is available.
You don't need to trust us; you can check the encryption yourself!
Deduplication: only the unique data between your current files and encrypted archives is uploaded.
This reduces the bandwidth and storage required, saving you money!

Tarsnap runs on UNIX-like operating systems (BSD, Linux, macOS, Cygwin, etc).

Tarsnap uses a prepaid model based on actual usage:

Storage:	250 picodollars / byte-month of encoded data ($0.25 / GB-month)
Bandwidth:	250 picodollars / byte of encoded data ($0.25 / GB)

There are no other fees — Tarsnap has no fixed costs or minimum monthly fees.

Consider a typical backup scenario:

Alice begins a backup, which takes a complete snapshot of her files.
She does not need to decide whether to do a "full backup" or "incremental backup". [Why?]
Tarsnap automatically finds the unique data within her files.
Only this data is uploaded and stored. [How?]
Alice pays less than $5/month.
Even though she has thousands of daily backups, adding up to several terabytes of non-unique data. [Why?]
Alice's data is secure.
Even if an attacker (Mallory) breaks into Tarsnap's storage, he lacks her private keys and thus cannot read or modify her data. [Why?]

Changes in this version compared to 1.0.38:

tarsnap 1.0.38 (but not earlier versions) would exit with an assertion failure after successfully creating an archive containing a file with "last modified" times prior to January 1st, 1970.
tarsnap 1.0.38 and earlier could crash if instructed to archive the contents of corrupt cpio or ar archives (via the @archive directive).
tarsnap 1.0.38 and earlier could crash if passed an invalidly encrypted key file.

You can see all of the changes between 1.0.38 and this version in our tarsnap git repository.