Which of the following is true?

A.
No successful attacks have been reported against double DES.

B.
The work factor of single DES is the same as for triple DES.

C.
The work factor of double DES is the same as for single DES.

D.
The work factor of triple DES is the same as for double DES.

Explanation:
The Meet-in-the-Middle attack has been successfully applied to double DES, and the work factor is
equivalent to that of single DES. Thus, answer “No successful attacks have been reported against
double DES” is incorrect. Answer “The work factor of triple DES is the same as for double DES” is
false because the work factor of triple DES is greater than that for double DES. In triple DES, three
levels of encryption and/or decryption are applied to the message. The work factor of double DES is
equivalent to the work factor of single DES. Answer “The work factor of single DES is the same as for

triple DES” is false because the work factor of single DES is less than for triple DES. In triple DES,
three levels of encryption and/or decryption are applied to the message in triple DES.