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    SubjectRe: [PATCH 7/14] random: Remove SA_SAMPLE_RANDOM from network drivers
    On May 5, 2006, at 12:42:35, Matt Mackall wrote:
    > Remove SA_SAMPLE_RANDOM from network drivers
    > /dev/random wants entropy sources to be both unpredictable and
    > unobservable. Network devices are neither as they may be directly
    > observed and controlled by an attacker. Thus SA_SAMPLE_RANDOM is
    > not appropriate.

    I thought I saw an analysis somewhere of why it was actually OK to
    include randomness from network devices (or even basically any
    interrupt source that isn't periodic on a fundamental hardware
    level). It had something to do with investigating interrupt arrival
    time from real-time network traffic; they hooked a logic analyzer of
    sorts up to the physical ethernet cable itself and to the system bus
    of the destination computer (and wrote software that recorded a TSC
    timestamp of every interrupt). Essentially the interaction between
    the occasional ethernet retransmission, variable internal network
    card latencies and queues, variable CPU-dependent interrupt
    latencies, critical sections in the OS, etc, plus the high-resolution
    nature of the TSC used for a seed value made it a chaotic system and
    basically cryptographically impossible to predict the interrupt
    data. It's possible that the analysis I saw was later proven
    incorrect; but I'd be interested if you've seen some paper or
    research on the topic that I haven't, I'd be interested in references.

    Kyle Moffett

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