Question

. The total processing speed of microprocessors (based on clock rate and number of circuits) is doubling roughly every year. Today, a symmetric session key needs to be 100 bits long to be considered strong. How long will a symmetric session key have to be in 30 years to be considered strong?

Answer 1

Answer:

130 bits

Explanation:

If the length of a key = N bits

Total number of key combinations = $\frac{2^{N} }{2}$

For a key length of 100, the total number of key combinations will be  $\frac{2^{100} }{2} = 2^{99}$ combinations. This is a whole lot and it almost seems impossible to be hacked.

The addition of  one bit to the length of the symmetric key in 1 year is sufficient to make the key strong, because even at double its speed, the processor can still not crack the number of combinations that will be formed.

Therefore, if a bit is added to the key length per year, after 30 years, the length of the symmetric session key will be 130 bits.