Like any sophisticated system, a large number of technical decisions went into building Tarsnap; in Tarsnap's case, these ranged from the question of what currency unit to use to the problem of constructing a key derivation function resistant to brute force attacks using custom hardware.

While none of these details are likely to be vitally important for Tarsnap users, they are nonetheless interesting, and potentially useful to Tarsnap users and non-users alike; so this corner of the Tarsnap website is a dumping ground for assorted Tarsnap-related details:

• Why are Tarsnap prices defined in picodollars and accounted in attodollars?
• Why is 1 GB equal to 10^9 bytes, not 2^30 bytes?
• How does Tarsnap use all of its cryptographic keys to keep data safe?
• What does the Tarsnap client do?
• What metadata does Tarsnap store?
• How efficient is deduplication?

For an overview of the algorithms used in Tarsnap, please see the slides for From bsdtar to tarsnap: Building an online backup service, presented at EuroBSDcon 2013.

For information about using the Tarsnap client, please see our documentation, including our detailed help for advanced usage.

Think something about Tarsnap is interesting enough that it should be explained here? Contact the author and let him know.