DES uses a 56-bit key. Let's say you encrypt a message using single DES. With a 56-bit key there are 2^56 possible different keys. On average an attacker would only need to try half this number of keys to guess the correct key and break the system. If a cryptanalyst can try 1,000,000 keys per second, how long on average would it take to discover the key and recover the plaintext?

1. Select about 30 minutes as your answer
2. about 30 minutes
3. Select about 1142 years as your answer
4. about 1142 years
5. Select about 250 years as your answer
6. about 250 years
7. Select about 2140 years as your answer
8. about 2140 years
9. Select as your answer
10. None of the above