Suppose a cipher uses an 8-character mixed-case alphanumeric key (0-9, a-z, and A-Z).

(a) What is the size of the keyspace (i.e., how many unique keys are possible)?

(b) What is the approximate strength of the key, measured in bits? Hint: rewrite the size of the keyspace as a power of two.

(c) If a particular computer can test 240 keys per second, how long will it take (on average) to guess the key of this cipher? 5.

Consider that the 8-character key from the previous problem would take up 64 bits if stored as an ASCII string. However, in this scenario, not every bit would contribute to the strength of the key. Assume the cipher is upgraded to use all 64 bits.

(a) What is the new size of the keyspace?

(b) How much time would it take to crack the new version of the cipher (if able to test 240 keys per second)?