Quantum crypto broken?

Daniel Roethlisberger daniel at roe.ch
Mon May 13 07:54:11 EDT 2002

Michael_Heyman at NAI.com <Michael_Heyman at NAI.com> wrote:
> This article leads one to believe that one can eavesdrop without
> being detected and with nearly 5/6ths confidence of the data on
> a quantum crypto communication. This is in contrast to the claim
> to fame of quantum crypto that the receiver will know if there
> is an eavesdropper. (This is what makes quantum crypto work when
> all public key crypto gets broken.)

On a sidenote, keep in mind that a success rate of 5/6th is not
nearly good enough to successfully copy (intercept) multiple
photons (bits). 5/6 = 83% per bit gives you (5/6)^8 = 23%
confidence per byte, or (5/6)^16 = 5% for 2 bytes, or even
(5/6)^128 = 7E-9% for 16 bytes which clearly is not as alarming as
the 5/6th look in the first place; real world transmissions would
surely be large enough to get that interception confidence rate
down. On the other hand, that confidence rate may well be expected
to get much better than 5/6th by the time we actually use quantum
crypto in the real world.


   Daniel Roethlisberger <daniel at roe.ch>
   PGP Key ID 0x8DE543ED with fingerprint
   6C10 83D7 2BB8 D908 10AE  7FA3 0779 0355 8DE5 43ED

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