keithw/mosh — pull request #80 by kmcallister (2012-03-25 00:53:46+00:00)
Title: Kill the session after encrypting 2^47 blocks

> Both the privacy and the authenticity properties of OCB degrade as per s^2 / 2^128, where s is the total number of blocks that the adversary acquires.... In order to ensure that s^2 / 2^128 remains small, a given key should be used to encrypt at most 2^48 blocks (2^55 bits or 4 petabytes)

-- http://tools.ietf.org/html/draft-krovetz-ocb-03

We deem it unlikely that a legitimate user will send 4 PB through a Mosh session. If it happens, we simply kill the session. The server and client use the same key, so we actually need to die after 2^47 blocks.

Closes #77.