the alphabet cipher (#11)

Author: irfanshadikrishad

README.md

@@ -24,5 +24,7 @@ console.log(ceaser.encrypt("hello world"))
 - Atbash Cipher
 - Playfair Cipher
 - Vigenere Cipher
+- The Alphabet Cipher
+- & more coming soon ...
 
 #### Thanks for visiting (>'-'<)

dist/Cipher.d.ts

@@ -2,11 +2,13 @@ import { Caesar } from "./ciphers/Caesar.js"
 import { Atbash } from "./ciphers/Atbash.js"
 import { Playfair } from "./ciphers/Playfair.js"
 import { Vigenere } from "./ciphers/Vigenere.js"
+import { Alphabet } from "./ciphers/Alphabet.js"
 export declare abstract class Cipher {
   static Caesar: typeof Caesar
   static Atbash: typeof Atbash
   static Playfair: typeof Playfair
   static Vigenere: typeof Vigenere
+  static Alphabet: typeof Alphabet
   abstract encrypt(text: string): string
   abstract decrypt(text: string): string
 }

dist/ciphers/Alphabet.d.ts

@@ -0,0 +1,22 @@
+import { Cipher } from "../Cipher.js"
+export declare class Alphabet extends Cipher {
+  private keyword
+  private static alphabet
+  constructor(keyword: string)
+  /**
+   * Encrypts a message using the Alphabet Cipher.
+   * @param message - The plaintext message to encrypt.
+   * @returns The encrypted ciphertext.
+   */
+  encrypt(message: string): string
+  /**
+   * Decrypts a message using the Alphabet Cipher.
+   * @param ciphertext - The encrypted message to decrypt.
+   * @returns The original plaintext message.
+   */
+  decrypt(ciphertext: string): string
+  /**
+   * Generates the Vigenère table for encoding and decoding.
+   */
+  private static getVigenereTable
+}

dist/ciphers/Alphabet.js

@@ -0,0 +1,65 @@
+import { Cipher } from "../Cipher.js"
+export class Alphabet extends Cipher {
+  constructor(keyword) {
+    super()
+    this.keyword = keyword.toLowerCase()
+  }
+  /**
+   * Encrypts a message using the Alphabet Cipher.
+   * @param message - The plaintext message to encrypt.
+   * @returns The encrypted ciphertext.
+   */
+  encrypt(message) {
+    message = message.toLowerCase()
+    const table = Alphabet.getVigenereTable()
+    let result = ""
+    for (let i = 0; i < message.length; i++) {
+      const msgChar = message[i]
+      const keyChar = this.keyword[i % this.keyword.length]
+      if (!Alphabet.alphabet.includes(msgChar)) {
+        result += msgChar // Preserve non-alphabet characters
+        continue
+      }
+      const row = Alphabet.alphabet.indexOf(keyChar)
+      const col = Alphabet.alphabet.indexOf(msgChar)
+      result += table[row][col]
+    }
+    return result
+  }
+  /**
+   * Decrypts a message using the Alphabet Cipher.
+   * @param ciphertext - The encrypted message to decrypt.
+   * @returns The original plaintext message.
+   */
+  decrypt(ciphertext) {
+    ciphertext = ciphertext.toLowerCase()
+    const table = Alphabet.getVigenereTable()
+    let result = ""
+    for (let i = 0; i < ciphertext.length; i++) {
+      const cipherChar = ciphertext[i]
+      const keyChar = this.keyword[i % this.keyword.length]
+      if (!Alphabet.alphabet.includes(cipherChar)) {
+        result += cipherChar // Preserve non-alphabet characters
+        continue
+      }
+      const row = Alphabet.alphabet.indexOf(keyChar)
+      const col = table[row].indexOf(cipherChar)
+      result += Alphabet.alphabet[col]
+    }
+    return result
+  }
+  /**
+   * Generates the Vigenère table for encoding and decoding.
+   */
+  static getVigenereTable() {
+    const table = []
+    for (let i = 0; i < 26; i++) {
+      table[i] = Alphabet.alphabet
+        .slice(i)
+        .split("")
+        .concat(Alphabet.alphabet.slice(0, i).split(""))
+    }
+    return table
+  }
+}
+Alphabet.alphabet = "abcdefghijklmnopqrstuvwxyz"

dist/index.js

@@ -3,8 +3,10 @@ import { Caesar } from "./ciphers/Caesar.js"
 import { Atbash } from "./ciphers/Atbash.js"
 import { Playfair } from "./ciphers/Playfair.js"
 import { Vigenere } from "./ciphers/Vigenere.js"
+import { Alphabet } from "./ciphers/Alphabet.js"
 Cipher.Caesar = Caesar
 Cipher.Atbash = Atbash
 Cipher.Playfair = Playfair
 Cipher.Vigenere = Vigenere
+Cipher.Alphabet = Alphabet
 export { Cipher }

src/Cipher.ts

@@ -2,12 +2,14 @@ import { Caesar } from "./ciphers/Caesar.js"
 import { Atbash } from "./ciphers/Atbash.js"
 import { Playfair } from "./ciphers/Playfair.js"
 import { Vigenere } from "./ciphers/Vigenere.js"
+import { Alphabet } from "./ciphers/Alphabet.js"
 
 export abstract class Cipher {
   static Caesar: typeof Caesar
   static Atbash: typeof Atbash
   static Playfair: typeof Playfair
   static Vigenere: typeof Vigenere
+  static Alphabet: typeof Alphabet
 
   abstract encrypt(text: string): string
   abstract decrypt(text: string): string

src/ciphers/Alphabet.ts

@@ -0,0 +1,79 @@
+import { Cipher } from "../Cipher.js"
+
+export class Alphabet extends Cipher {
+  private keyword: string
+  private static alphabet = "abcdefghijklmnopqrstuvwxyz"
+
+  constructor(keyword: string) {
+    super()
+    this.keyword = keyword.toLowerCase()
+  }
+
+  /**
+   * Encrypts a message using the Alphabet Cipher.
+   * @param message - The plaintext message to encrypt.
+   * @returns The encrypted ciphertext.
+   */
+  encrypt(message: string): string {
+    message = message.toLowerCase()
+    const table = Alphabet.getVigenereTable()
+    let result = ""
+
+    for (let i = 0; i < message.length; i++) {
+      const msgChar = message[i]
+      const keyChar = this.keyword[i % this.keyword.length]
+
+      if (!Alphabet.alphabet.includes(msgChar)) {
+        result += msgChar // Preserve non-alphabet characters
+        continue
+      }
+
+      const row = Alphabet.alphabet.indexOf(keyChar)
+      const col = Alphabet.alphabet.indexOf(msgChar)
+      result += table[row][col]
+    }
+
+    return result
+  }
+
+  /**
+   * Decrypts a message using the Alphabet Cipher.
+   * @param ciphertext - The encrypted message to decrypt.
+   * @returns The original plaintext message.
+   */
+  decrypt(ciphertext: string): string {
+    ciphertext = ciphertext.toLowerCase()
+    const table = Alphabet.getVigenereTable()
+    let result = ""
+
+    for (let i = 0; i < ciphertext.length; i++) {
+      const cipherChar = ciphertext[i]
+      const keyChar = this.keyword[i % this.keyword.length]
+
+      if (!Alphabet.alphabet.includes(cipherChar)) {
+        result += cipherChar // Preserve non-alphabet characters
+        continue
+      }
+
+      const row = Alphabet.alphabet.indexOf(keyChar)
+      const col = table[row].indexOf(cipherChar)
+      result += Alphabet.alphabet[col]
+    }
+
+    return result
+  }
+
+  /**
+   * Generates the Vigenère table for encoding and decoding.
+   */
+  private static getVigenereTable(): string[][] {
+    const table: string[][] = []
+    for (let i = 0; i < 26; i++) {
+      table[i] = Alphabet.alphabet
+        .slice(i)
+        .split("")
+        .concat(Alphabet.alphabet.slice(0, i).split(""))
+    }
+    return table
+  }
+}

src/index.ts

@@ -3,10 +3,12 @@ import { Caesar } from "./ciphers/Caesar.js"
 import { Atbash } from "./ciphers/Atbash.js"
 import { Playfair } from "./ciphers/Playfair.js"
 import { Vigenere } from "./ciphers/Vigenere.js"
+import { Alphabet } from "./ciphers/Alphabet.js"
 
 Cipher.Caesar = Caesar
 Cipher.Atbash = Atbash
 Cipher.Playfair = Playfair
 Cipher.Vigenere = Vigenere
+Cipher.Alphabet = Alphabet
 
 export { Cipher }

tests/alphabet.test.ts

@@ -0,0 +1,10 @@
+import { Cipher } from "../src/index"
+
+test(`The Alphabet Cipher`, () => {
+  const alphabet = new Cipher.Alphabet("keyword")
+  const plaintext = "hello world"
+  const enc = alphabet.encrypt(plaintext)
+  const dec = alphabet.decrypt(enc)
+
+  expect(dec).toBe(plaintext)
+})