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    SubjectRe: [PATCH v5 0/7] /dev/random - a new approach
    On Mon, Jun 20, 2016 at 09:00:49PM +0200, Stephan Mueller wrote:
    >
    > The time stamp maintenance is the exact cause for the correlation: one HID
    > event triggers:
    >
    > - add_interrupt_randomness which takes high-res time stamp, Jiffies and some
    > pointers
    >
    > - add_input_randomness which takes high-res time stamp, Jiffies and HID event
    > value
    >
    > The same applies to disk events. My suggestion is to get rid of the double
    > counting of time stamps for one event.
    >
    > And I guess I do not need to stress that correlation of data that is supposed
    > to be entropic is not good :-)

    What is your concern, specifically? If it is in the entropy
    accounting, there is more entropy in HID event interrupts, so I don't
    think adding the extra 1/64th bit of entropy is going to be problematic.

    If it is that there are two timestamps that are closely correleated
    being added into the pool, the add_interrupt_randomness() path is
    going to mix that timestamp with the interrupt timings from 63 other
    interrupts before it is mixed into the input pool, while the
    add_input_randomness() mixes it directly into the pool. So if you
    think there is a way this could be leveraged into attack, please give
    specifics --- but I think we're on pretty solid ground here.

    Cheers,

    - Ted

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