Assignment

Goals

1. To use bitwise functions in a program. ?
2. To implement encryption of the data in a file. ?
3. To use the Vector class. ?
4. This is part of your final exam.

You are going to perform an encryption of the data in the file. The first step is to swap the bits in each character, but since the technique of swapping bits is based on the position of the letter in the file, the letter frequency should change, so the data is more secure. This is a breakable cipher.

Instructions

1. Open a text file containing any text you wish (provided it is appropriate for campus). Pick a printable character as the end of file marker such as # or $.

2. Read whitespace characters as well as printable characters from your file and read the entire file into a vector. Leave the original whitespace characters in the vector, do not add or remove any characters.

3. Process the vector one character at a time. You will need to keep track of their place in the vector.

4. For each character do the following:

a. Using the index of the character (count the places in the file).

i. For the characters with an even position in the file (those with an even index, 0th, 2nd, 4th, 6th, etc.):

1. Encrypt the character by switching the value in bits 2 and 4. a. Switch of bit places are as follows:

b. The encrypted value would be: 1110 0111

2. Use bitwise operations to do this.

3. Replace the original character with the encrypted character in your vector.

ii. For the remaining characters with an odd position in the file (those with an odd index, 1st, 3rd, 5th, etc.):

1. Encrypt the character by switching the value in bits 1 and 3. a. Switch of bit places are as follows:

b. The encrypted value would be: 1111 1001

2. Use bitwise operations to do this.

3. Replace the original character with the encrypted character in your vector.

b. Do this for all the characters in the file.

c. Add the end of file marker to the end of the vector but do not switch its bits.

5. Write out the encrypted data from the vector to a new file, e.g. output.txt.

6. The switched characters of printable characters should also be printable. Leave the whitespace in the vector, they will remain whitespace

7. I expect this to take under 300 lines of code including comments, do not embellish the requirements.

Testing and Output.

• Test your program with text files of length 0, 140 and 500 characters. Rename and keep the input and output files from each test. E.g. output1.txt