A certain cryptography vendor was providing an encryption technology that was breakable within 10 hours. Considering the continuous increase in computer speed, the company decided to increase the size

A certain cryptography vendor was providing an encryption technology that was breakable within 10 hours. Considering the continuous increase in computer speed, the company decided to increase the size of the encryption key so that the time to break the encryption become more than 250 hours. What should be the minimum key size increase to meet this objective? Hint: Normally, the increase of a single bit in the size of the encryption key doubles the amount of needed computations