Question

An ECB mode of operation that incorporates padding encrypts a 200 bit message using DES. What is the necessary amount of padding in bytes

Group of answer choices

0

7

8

none of the above

Answer 1

An ECB mode of operation that incorporates padding encrypts a 200 bit message using DES. So the necessary amount of padding is 8 bytes.

because using DES with a single 64-bit key is definitely no longer recommended, but we use it here for simplicity to demonstrate the principle of padding for an 8-byte block. It is easy to extend this to a more-secure 192-bit Triple DES key or 256-bit Blowfish key. Similarly we use ECB mode to avoid the complications of initialization vectors.