1. Assignment 2
DES implementation

2. DES Implementation Design a DES encryption/decryption program
DES encrypts and decrypts data in 64-bit blocks, using a 64-bit key (the effective key strength is only 56 bits).

3. DES Implementation Input Output From the standard input(stdin).
The first line indicates encryption(E) or decryption(D).
The second line contains the key of format "XX XX XX XX XX XX XX XX“ in hexadecimal system.
The third line contains a 64-bit data block of the same format.
Output
It shows in the standard output(stdout).
The output is a line of the same format as above, which represents the encrypted or decrypted data.

4. DES Implementation Sample Input Sample Output E <- encryption
AB CD EF <- key
70 6C E <- plaintext
Sample Output
6B D2 8F E EE 94 <- ciphertext

5. DES Implementation Sample Input Sample Output D <- decryption
AB CD EF <- key
6B D2 8F E EE 94 <- ciphertext
Sample Output
70 6C E <- plaintext

6. DES Implementation Requirements of the program
Programming Languages: C/C++
These lines are added at the beginning of your code
//File Name: _des.c
//Author: 劉用翔
// Address:
Your program is designed to show nothing but the required output, and it terminates after one encryption or decryption is done.

7. DES Implementation Requirements of the report
Less than one page is suggested.
Development Environment: including OS and compiler, and others if necessary.
Screenshot: the snapshot of the execution of encryption and decryption of your program(s).
Any other words you want to write down.

8. DES Implementation Due Hand in via E-mail 11/2/2008 23:59 pm (Sunday)
Attach a compressed file ( zip) which contains source code(s), report, and the executable file(s).

9. DES Implementation DES Algorithm References See note.