At 03:15 PM 6/8/2007, you wrote:
>Is this true for what the authors are decribing (forgive my ignorance)?
>
>'Forward CRC':
>|------------------->
>
>'Reverse CRC':
><-------------------|
In this case, it's dependent upon the file length.
Recall how a CRC works. For a bit stream b_i, treat the b_i as
coefficients of a polynomial P(x). The CRC value is P(x) modulo p(x). Let
N be the file length. Running the file in reverse is equivalent to the map
b_i --> b_{ N - 1 - i }
This has the same effect as
P(x) -> X^{ N } * P(1/x)
There are more details, but that's the essence of it.
Eric
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