Cryptography Reference
In-Depth Information
4.16.
The minimum key length for the AES algorithm is 128 bit. Assume that a
special-purpose hardware key-search machine can test one key in 10 ns on one pro-
cessor. The processors can be parallelized. Assume further that one such processor
costs $10, including overhead. (Note that both the processor speed and the prize are
rather optimistic assumptions.) We assume also that Moore's Law holds, according
to which processor performance doubles every 18 months.
How long do we have to wait until an AES key search machine can be built
which breaks the algorithm on average in one week and which doesn't cost more
than $1 million?
4.17.
For the following, we assume AES with 192-bit key length. Furthermore, let
us assume an ASIC which can check 3
10
7
ยท
keys per second.
1. If we use 100,000 such ICs in parallel, how long does an average key search take?
Compare this period of time with the age of the universe (approx. 10
10
years).
2. Assume Moore's Law will still be valid for the next few years, how many years
do we have to wait until we can build a key search machine to perform an average
key search of AES-192 in 24 hours? Again, assume that we use 100,000 ICs in
parallel.
