p3-ciphers

EECS 183 Project 3: Ciphers — Student Quickstart

Full specification (all details + sample runs): Full Spec

This page is a shorter, student-first version of the full spec. It keeps every requirement, but organizes them for faster onboarding.

Note: you will need to use the details in the full specification to complete the project.

0) Logistics (Dates, Grading, Submissions)

Due date: Friday, February 27, 2026 at 8:00 p.m. (accepted until 11:59:59 p.m.)

Autograder: Direct autograder link

Early bonus (autograder score):

• Last submission on Wednesday, February 25: +5%
• Last submission on Thursday, February 26: +2.5%

Grading:

• 10 points testing (test.cpp)
• 60 points correctness
• 10 points style

Submissions:

• 4 submissions per day with feedback
• 1 extra wildcard submission (once during the project period)
• Best submission counts for style
• If multiple submissions tie in score, the last of those is used for style

1) Big Picture (What You’re Building)

You will implement three ciphers and a menu-driven driver program:

• Caesar cipher
• Vigenere cipher
• Polybius Square
• A ciphers() program that asks the user what to do and prints the result
• A test suite in test.cpp

2) Files You’re Given (and One You Create)

Download the starter files using this link.

Note: the project will not compile until test.cpp exists and defines startTests().

Important constants in utility.h:

• SIZE = 6 (Polybius grid size)
• ALNUM = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

3) Read the RME Comments Like Contracts

Every function declaration in the headers has an RME comment:

• Requires: preconditions the caller must satisfy.
• Modifies: what the function is allowed to change.
• Effects: what the function returns or does.

If your tests or ciphers() violate a Requires clause, the autograder will penalize you. Treat RMEs like a contract between the caller and callee.

4) Collaboration and Partnering

Allowed collaboration:

• Help understanding course concepts
• Discuss the spec and design ideas
• Help debug or interpret compiler errors

Not allowed:

• Copying or deriving code from others
• Sharing your code in any form (public or private)
• Collaborating so solutions are identifiably similar
• Receiving help that tells you what to write
• Sharing test cases submitted for grading

If unsure, ask course staff first.

Partnering:

• You may work with one other currently enrolled EECS 183 student
• You must register your group on the autograder before submitting
• You cannot change partners or add a partner mid-project
• Group gets the same submit limit (no extra submits)
• Partners share an autograder and submissions - you can and should have the same code as your partner
• Review partner/late-day policies: partner guidelines

5) Suggested Implementation Order

This order reduces confusion and makes later functions easier:

1. utility.cpp
2. caesar.cpp
3. vigenere.cpp
4. polybius.cpp
5. ciphers.cpp

6) Test Suite Basics

You must create test.cpp with a startTests() function. Write tests before you implement each function. There is no main() in test.cpp.

Full details: Test Suite

Testing notes:

• Do not call functions with inputs that violate their Requires clauses.
• The autograder runs your test.cpp against both correct and buggy staff implementations and compares output.
• If the outputs differ, you exposed a bug. You do not need to find all bugs to get full testing points.
• Style is not graded in test.cpp.

Minimal test.cpp skeleton:

#include "utility.h"
#include "caesar.h"
#include "vigenere.h"
#include "polybius.h"
#include <iostream>
#include <string>

using namespace std;

void startTests() {
    // call your test functions here
}

Functions to test:

• toUpperCase()
• removeNonAlphas()
• removeDuplicate()
• charToInt()
• shiftAlphaCharacter()
• caesarCipher()
• vigenereCipher()
• fillGrid()
• mixKey()
• findInGrid()
• polybiusSquare()

Bug IDs the autograder may report (names only):

• CAESAR_SHIFTALPHACHARACTER1
• CAESAR_SHIFTALPHACHARACTER2
• CAESARCIPHER
• UTILITY_CHARTOINT
• UTILITY_REMOVEDUPLICATE
• UTILITY_REMOVENONALPHAS1
• UTILITY_REMOVENONALPHAS2
• UTILITY_TOUPPERCASE
• POLYBIUS_FILLGRID
• POLYBIUS_FINDINGRID
• POLYBIUS_MIXKEY
• POLYBIUSSQUARE
• VIGENERECIPHER

7) Cipher Rules (Short Version)

Full details: Ciphers section

Caesar Cipher

Functions:

• shiftAlphaCharacter(char c, int n)
• caesarCipher(string original, int key, bool encrypt)

Vigenere Cipher

Steps:

• Convert keyword to uppercase
• Remove non-letters from keyword
• Repeat keyword across letters only in the message
• Shift letters by keyword letter distance (A=0, B=1, …)
• Preserve case in the message
• Non-letters unchanged

Function:

• vigenereCipher(string original, string keyword, bool encrypt)

Requires:

• keyword must contain at least one alphabetical character

Polybius Square

Rules:

• Grid is 6x6 using ALNUM (A–Z then 0–9)
• Build a mixed grid using a key with no duplicates
• Encrypt by replacing each character with row/column digits
• Decrypt by reversing those coordinates
• Spaces are allowed and stay as spaces

Functions:

• mixKey(string key)
• fillGrid(char grid[SIZE][SIZE], string content)
• findInGrid(char c, char grid[SIZE][SIZE])
• polybiusSquare(char grid[SIZE][SIZE], string key, string original, bool encrypt)

Requires:

• key is uppercase, alphanumeric, no duplicates
• original uses only uppercase alphanumeric or spaces

Note:

• Decrypted Polybius output being all uppercase is expected and acceptable.

8) ciphers() Input Rules (Very Important)

Your ciphers() function must validate user input to avoid violating RMEs.

Full details: Error handling in ciphers()

Prompts (exact text + a single trailing space):

Choose a cipher (Caesar, Vigenere, or Polybius):
Encrypt or decrypt:
Enter a message:
What is your key:
The encrypted message is:
The decrypted message is:

Accepted cipher inputs (case-insensitive):

• caesar or c
• vigenere or v
• polybius or p

Accepted mode inputs (case-insensitive):

• encrypt or e
• decrypt or d

Error handling:

• Invalid cipher -> print Invalid cipher! and return
• Invalid mode -> print Invalid mode! and return
• Caesar: you may assume the key is an integer when Caesar is selected
• Vigenere: keyword must contain at least one letter, else Invalid key!
• Polybius message: must be alphanumeric or space; convert to uppercase before calling polybiusSquare, else Invalid message!
• Polybius key: must be alphanumeric only, uppercase, no duplicates; uppercase + remove duplicates before calling polybiusSquare, else Invalid key!

Input tips:

• Prefer getline to read messages/keys that may include spaces.
• Accept c, v, p, e, d (any case) as shorthand.

Sample runs: Sample Output

9) Function Dependency Map (Who Calls What)

Full details: Function Table

10) Style and Autograder Reminders

Full details: Style Checklist

Style essentials:

• No global variables
• No magic numbers like 26 or 65
• No break / continue in loops
• No if (someBool == true) comparisons
• 80 characters per line max
• Write helpful comments
• Do not edit provided header files
• Keep RMEs above function declarations (if you add helper functions in ciphers.cpp, add RMEs above those declarations)
• Do not use numeric ASCII values for characters (use 'A', 'a', etc.)

Autograder reminders:

• Submit: caesar.cpp, utility.cpp, test.cpp, ciphers.cpp, polybius.cpp, vigenere.cpp
• Whitespace differences can fail tests
• You get 4 submissions per day + 1 wildcard submission
• Best submission counts for style
• If multiple submissions tie in score, the last of those is used for style

11) Recommended Timeline (Winter 2026)

12) Fast Start Checklist

• Download and unzip starter files
• Create test.cpp with startTests()
• Implement and test utility.cpp
• Implement and test caesar.cpp
• Implement and test vigenere.cpp
• Implement and test polybius.cpp
• Implement and test ciphers.cpp
• Submit early and often

13) Warm-Up Questions (Quick Review)

• What does % do?
• Difference between char and string?
• How to get a string’s length?
• How to get the first, last, or nth character?
• How to represent an empty string?
• How to concatenate strings?
• Difference between 0 and '0'?
• How to check if a character is lowercase, uppercase, alphabetic, or alphanumeric?

14) Library Notes You Can Use

• cctype functions like isalpha, isdigit, isspace return non-zero for true. Use if (isalpha(ch)), not if (isalpha(ch) == true).
• to_string(int) converts an integer to a string. It does not convert a char.

15) Optional Challenge

• S’More (optional): Project 3 S’More