Security in Computing

Security in Computing

In this assignment you’ll write a program that calculates the checksum for the text in a file. Your
program will take two command line parameters. The first parameter will be the name of the input
file for calculating the checksum. The second parameter will be for the size of the checksum (8, 16,
or 32 bits). The program must generate output to the console (terminal) screen as specified below.

Command Line Parameters
1. Your program must compile and run from the command line.
2. The program executable must be named “checksum” (all lower case, no spaces or file
3. Input the required file names as command line parameters. Your program may NOT
prompt the user to enter the file names. The first parameter must be the name of the
file used for calculating the checksum, as described below. The second parameter must
be the size, in bits, of the checksum. The sample run command near the end of this
document contains an example of how the parameters will be entered.
4. Your program should open the two files, echo the processed input to the screen, make
the necessary calculations, and then output the ciphertext to the console (terminal)
screen in the format described below.
Program Submission Instructions:
• You must submit your source code file
• The source code file must be submitted in Webcourses from the assignment page
• All source code must be in exactly one file of type .c, .cpp, or .java
Checksum size
The checksum size is a single integer, passed as the first command line argument. The valid values
are the size of the checksum, which can be 8, 16, or 32 bits. Therefore, if the first parameter is not
one of the valid values, the program should advise the user that the value is incorrect with a
message formatted as shown below:
printf(“Valid checksum sizes are 8, 16, or 32\n”);
The message should be sent to STDERR.
Format of the input file
The input file will consist of the valid ASCII characters associated with the average text file. This
includes punctuation, numbers, special characters, and whitespace.
Output Format
The program must output the following to the console (terminal) screen:
1. Echo the input file
2. Print the checksum.
The echoed input text should be in rows of exactly 80 characters per row (not counting the
NEWLINE character), except for the last row, which may possibly have fewer. These characters
should correspond to the input text. The checksum line should be formatted as follows:
X bit checksum is Y for all ZZZ chars
Using the following:
printf(“%2d bit checksum is %8lx for all %4d chars\n”,
checkSumSize, checksum, characterCount);
Where X is the checksum size (checkSumSize) of 8, 16, or 32, Y is the calculated checksum
(checksum), and ZZZ is the character count (characterCount) of the input file. Note that the
checksums are masked to print the appropriate sizes such as two hex characters for 8 bits, 4 hex
characters for the 16 bit checksum, and 8 hex characters for 32 bit checksum. (Note that the format
specifier for the checksum is %8lx, or the percent sign, the number 8, the letter l, and the letter x.)
What to submit to WebCourses
You must submit this assignment’s source code, appropriately commented, via WebCourses.
Program Notes and Hints
Your program must read in an input text file that may contain uppercase letters, lowercase letters
and non-letter characters. Your program should then calculate the checksum appropriately for the
size specified in the command line. Specifically, if the checksum is 8 bits long, each character should
be used as the number to be added to the checksum. Likewise, if the checksum is 16 bits long, each
two characters should be added to the checksum. Note that there is a 50% chance that there will be
one character short on the input file. In that case use the character “X” (an uppercase X) as the pad
character. Similarly, if the checksum is 32 bits, use the same technique and character to pad the
input string appropriately with 1, 2, or 3 pad characters (X). Correspondingly, some adjustment to
the file termination character NEWLINE may be required to match the expected output files.
Sample Run Command
C or C++ program:
Prompt$ ./checksum inputText1.txt 8
Java program:
Prompt$ java checksum inputText1.txt 8
Grading Rubric
The total possible score for this program is 100 points. The following point values will be deducted
for the reasons stated:
[ -100 points ] Your program does not successfully compile from the command line with one of
these commands:
C program: prompt> gcc –o checksum checksum.c
C++ program: prompt> g++ –o checksum checksum.cpp
Java program: prompt> javac
Note: If you are submitting a Java program, the class file must be named “”
and the class name must be “checksum”.
[-100 point] The program does not accept input file names from the command line.
[ -90 points ] Your program does not run from the command line without error or produces no
[ -70 points ] The program compiles, runs, and outputs the input file (with a maximum of 80
characters per line), but crashes thereafter or produces no checksum output.
[ -25 points ] The program compiles, runs, echoes the input, and calculates the checksum, but the
checksum output is incorrect and it is not formatted correctly (not all input text or not a maximum
of 80 characters per line).
[ no deductions ] The program compiles, runs, echoes the inputs, generates encryption output, the
encryption output is correct (ignoring case), and it is formatted correctly (all lowercase letters, 80
letters per line).
Test Files
The following test files are included for your program testing. All of them are in the ZIP file names on Webcourses.
conventions File usage notes
inXXXX.txt Input text file. Contains text with a terminating NEWLINE (0x’0a’) NEWLINE
in c is “\n”.
sXXX-BaseXX.txt The expected output for each corresponding input file. For example, given
in10A.txt as input for an 8 bit checksum, the baseline output is s10A-Base8.txt.
Each of the input files has a corresponding baseline output.
sXXX-OutputXX.txt The captured output file for the given input file and checksum size.
Please note that the following:
1 Every input file has a single line of text terminated by the hex character ‘0A’ or the
NEWLINE character.
2 Some input files are less than 80 characters long, others aren’t.
3 More testing files are supplied than are used in the script.
4 After uploading the testing shell script (and corresponding files) remember to execute
the command chmod +x *.sh to grant execution privileges for the script.
5 The script is executed at the command line as follows:
./ checksum.c where the checksum program filename has the correct
extension for your submission.

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