8/20 I'm having a hard time figuring out some of the math behind
diffe-hellman. The "key", pardon the pun, to the security of
dh seems to be is that calculating g**(x*y) mod n is hard
for an attacker. Say x and y are small, less than 1024,
couldn't an attacker just precompute all possible K (and K')
based on n and g and then do a table lookup based on the X
and Y values that are exchanged to get K (or K')?
It seems to me that you need to make x and y quite large to
have any sort of confidence that K and K' are secure. BUT,
a large x and y means the compute time per key exchange is
exteremely long. What are commonly used upper bounds on x
and y?
Sorry, if my questions are exteremely simple, I don't have
a good handle on this material yet. |
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