CIS 3360 – Security In Computing Summer 2020 HW 2 Checksum

CIS 3360 – Security in Computing Summer 2020 HW #2 Checksum (100 points) In this assignment you'll write a program that calculates the checksum for the text in a file

In this assignment, you will develop a program that calculates the checksum for the text contained within a file. The program must accept two command-line parameters: the name of the input file and the desired checksum size, which can be 8, 16, or 32 bits. It should open the specified file, process its contents, and output a formatted representation of the input along with the computed checksum details.

The program's primary responsibilities include reading the input file, computing the checksum based on the specified size, and echoing the contents in rows of exactly 80 characters, except possibly the last line. After processing, it must display the checksum in hexadecimal format, formatted according to the checksum size, and include the total number of characters processed. The checksum calculation involves adding values of characters or groups of characters, with specific padding if necessary, as explained below.

Specifically, the program must:

• Accept the input filename and checksum size from the command line, rejecting invalid checksum sizes with an appropriate message.
• Read in the input file, which can contain any ASCII characters, including punctuation, numbers, special characters, and whitespace.
• Print the input contents to the console, formatted with a maximum of 80 characters per line.
• Calculate the checksum as follows:
  • If checksum size is 8 bits, sum each character's ASCII value modulo 256.
  • If checksum size is 16 bits, sum every two characters' ASCII values, padding with 'X' if necessary, and take modulo 65536.
  • If checksum size is 32 bits, sum every four characters' ASCII values, padding with 'X' as needed, and take modulo 2³².
• Display the output line: "X bit checksum is Y for all ZZZ chars", where X is checksum size, Y is the checksum in hexadecimal (formatted with leading zeros as needed), and ZZZ is the total character count.

The program must be named “checksum” in lowercase with no file extension, and must compile and run from the command line. It should produce the exact output format, including the maximum line length of 80 characters, and handle padding characters ('X') for incomplete groups of characters at the end of the file. Your implementation should include appropriate error handling for invalid checksum sizes and ensure that all input and output formatting adheres strictly to the specifications.

Paper For Above instruction

Data integrity verification is a fundamental aspect of computer security, wherein checksum algorithms play a critical role by detecting errors or tampering in transmitted or stored data. The checksum process involves summing or processing data segments to generate a fixed-size value that can be used to verify data authenticity and integrity during future comparisons. Developing an understanding of checksum calculations is vital in cybersecurity and data management, providing a layered safeguard against integrity violations.

The assignment requires the implementation of a checksum algorithm that accommodates varying data input sizes and checksum lengths. It emphasizes robust file handling, precise data processing, and meticulous output formatting, all of which are essential skills in cybersecurity programming. The core challenge involves handling data padding and ensuring that the checksum computation correctly reflects the length and content of the input file, especially in cases where the data length is not divisible by the checksum grouping size.

Implementing such a checksum involves reading the entire file into memory or processing it in streams. The character-by-character approach ensures that each byte is considered, and grouping strategies ensure proper segmentation for 16 and 32-bit checksum calculations. Padding characters are strategically used to complete the groupings when the data length is not a multiple of the group size, maintaining consistency and correctness in the checksum computation.

Adherence to output specifications is critical, especially in formatting the echoed input with a maximum of 80 characters per line, and displaying the checksum in a hexadecimal format with leading zeros. This uniform presentation enhances readability and comparability, which is crucial for security audits, troubleshooting, and integrity verification.

From a security perspective, such checksum algorithms are susceptible to certain attacks if used alone, but they are an essential component of layered security strategies. Combining checksum verification with encryption, hashing, or digital signatures amplifies the robustness of data protection mechanisms, making it infeasible for adversaries to alter data undetected.

References

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