Informatik 10

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====== Verschlüsselung ======
===== Cäsar-Verschlüsselung =====
<HTML>

<div class="java-online" style="height: 70vh; width: 100%" data-java-online="{'withBottomPanel': false, 'id': 'Cäsar1'}">

<script type="text/plain" title="Main.java">
char schlüssel = Input.readChar("Bitte geben Sie den Schlüssel ein:");
Cäsar cäsar = new Cäsar(schlüssel);

String plaintext = Input.readString("Welcher Text soll verschlüsselt werden?");
cäsar.encrypt(plaintext);

String ciphertext = cäsar.encrypt(plaintext);
println("\nVerschlüsselter Text:", Color.chocolate);
println(ciphertext);

println("\nZur Sicherheit nochmals entschlüsselt:", Color.chocolate);
println(cäsar.decrypt(ciphertext));


class Cäsar {
   
   int keyOffset;
   String alphabet = "abcdefghijklmnopqrstuvwxyzäöüßABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÜ ";

   public Cäsar(char key) {
      this.keyOffset = alphabet.indexOf(key);
   }

   public String encrypt(String plaintext) {
      String ciphertext = "";

      for (int index = 0; index < plaintext.length(); index++) {
         char plainCharacter = plaintext.charAt(index);
         int charIndex = alphabet.indexOf(plainCharacter);
         charIndex = (charIndex + keyOffset) % alphabet.length();

         ciphertext += alphabet.charAt(charIndex);
      }

      return ciphertext;

   }


   public String decrypt(String ciphertext) {
      String plaintext = "";

      for (int index = 0; index < ciphertext.length(); index++) {
         char plainCharacter = ciphertext.charAt(index);
         int charIndex = alphabet.indexOf(plainCharacter);
         charIndex = (charIndex - keyOffset + alphabet.length()) % alphabet.length();

         plaintext += alphabet.charAt(charIndex);
      }

      return plaintext;

      
   }


}</script>
</div>

</HTML>


===== Vigenère-Verschlüsselung =====
<HTML>

<div class="java-online" style="height: 70vh; width: 100%" data-java-online="{'withBottomPanel': false, 'id': 'Vigenere'}">

<script type="text/plain" title="Main.java">
String schlüssel = Input.readString("Bitte geben Sie den Schlüssel ein:");
Vigenere vigenere = new Vigenere(schlüssel);

String plaintext = Input.readString("Welcher Text soll verschlüsselt werden?");
vigenere.encrypt(plaintext);

String ciphertext = vigenere.encrypt(plaintext);
println("\nVerschlüsselter Text:", Color.chocolate);
println(ciphertext);

println("\nZur Sicherheit nochmals entschlüsselt:", Color.chocolate);
println(vigenere.decrypt(ciphertext));


class Vigenere {
   
   String key;
   String alphabet = "abcdefghijklmnopqrstuvwxyzäöüßABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÜ ";

   public Vigenere(String key) {
      this.key = key;
   }

   public String encrypt(String plaintext) {
      String ciphertext = "";
      int keyIndex = 0;

      for (int index = 0; index < plaintext.length(); index++) {
         char plainCharacter = plaintext.charAt(index);
         int charIndex = alphabet.indexOf(plainCharacter);

         int keyOffset = alphabet.indexOf(key.charAt(keyIndex));

         charIndex = (charIndex + keyOffset) % alphabet.length();

         ciphertext += alphabet.charAt(charIndex);
         keyIndex = (keyIndex + 1) % key.length();
      }

      return ciphertext;

   }


   public String decrypt(String ciphertext) {
      String plaintext = "";
      int keyIndex = 0;

      for (int index = 0; index < ciphertext.length(); index++) {
         char plainCharacter = ciphertext.charAt(index);
         int charIndex = alphabet.indexOf(plainCharacter);

         int keyOffset = alphabet.indexOf(key.charAt(keyIndex));
         charIndex = (charIndex - keyOffset + alphabet.length()) % alphabet.length();

         plaintext += alphabet.charAt(charIndex);
         keyIndex = (keyIndex + 1) % key.length();
      }

      return plaintext;

      
   }


}</script>
</div>

</HTML>