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| Bruce Stephens... |
 Posted: Mon Jul 06, 2009 5:12 am |
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adacrypt <austin.obyrne at (no spam) hotmail.com> writes:
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[quote:723bf05a27]Only Alice and Bob know this side however and she is reduced to
guessing which one of a theoretically infinite set of possible sides
is the right one for her to use.
[/quote:723bf05a27]
"theoretically infinite" doesn't really fit with practicalities. In
particular, modern digital computers are finite. (One can perform
certain computations involving infinities, but ultimately the computer's
only got a finite number of things.)
[...] |
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| rossum... |
| Posted: Mon Jul 06, 2009 7:41 am |
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On Mon, 6 Jul 2009 02:48:21 -0700 (PDT), adacrypt
<austin.obyrne at (no spam) hotmail.com> wrote:
[quote:a064229857]Eve knows one side of a triangle and can only solve this triangle and
decrypt the cipher text item that the triangle sides represent by
knowing one more side. Only Alice and Bob know this side however and
she is reduced to guessing which one of a theoretically infinite set
of possible sides is the right one for her to use. This is the
essence of vector cryptography.
As Bruce has pointed out, "theoretically infinite" is of no use in a[/quote:a064229857]
practical implementation. If your implementation uses 3D integer
vectors then with 64 bit integers Eve has to guess 3 x 64 = 192 bits.
With 128 bit integers Eve has to guess 3 x 128 = 384 bits. Neither of
these are infinite in practice.
You also need to bear in mind the impact of unicity distance for any
messages longer than the key. In the 384 bit example, this is any
message longer than 384/8 = 48 characters; shorter than a single
Tweet.
rossum |
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| WTShaw... |
| Posted: Mon Jul 06, 2009 11:52 pm |
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On Jul 6, 8:41 am, rossum <rossu... at (no spam) coldmail.com> wrote:
[quote:509a97cc48]On Mon, 6 Jul 2009 02:48:21 -0700 (PDT), adacrypt
austin.oby... at (no spam) hotmail.com> wrote:
Eve knows one side of a triangle and can only solve this triangle and
decrypt the cipher text item that the triangle sides represent by
knowing one more side. Only Alice and Bob know this side however and
she is reduced to guessing which one of a theoretically infinite set
of possible sides is the right one for her to use. This is the
essence of vector cryptography.
As Bruce has pointed out, "theoretically infinite" is of no use in a
practical implementation. If your implementation uses 3D integer
vectors then with 64 bit integers Eve has to guess 3 x 64 = 192 bits.
With 128 bit integers Eve has to guess 3 x 128 = 384 bits. Neither of
these are infinite in practice.
You also need to bear in mind the impact of unicity distance for any
messages longer than the key. In the 384 bit example, this is any
message longer than 384/8 = 48 characters; shorter than a single
Tweet.
rossum
[/quote:509a97cc48]
"There you go again." Radians, perhaps...but bits as restrictions on
units of angularity and all numbers: LOL.
What is cleverly missing in this thread is a clear example, cut to
degrees and crude figures that work. The effort is unfulfilled
without it, then he can step up the ante. |
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