From d5ddc351d8bfa6f1a80bdc8f41b945b612ea8c08 Mon Sep 17 00:00:00 2001
From: Hassan <hassan.elseoudy@gmail.com>
Date: Tue, 28 Jan 2020 19:35:16 +0200
Subject: [PATCH 1/2] Simple Substitution Cipher Algorithm added.

---
 ciphers/SimpleSubstitutionCipher.java | 97 +++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 ciphers/SimpleSubstitutionCipher.java

diff --git a/ciphers/SimpleSubstitutionCipher.java b/ciphers/SimpleSubstitutionCipher.java
new file mode 100644
index 00000000..983bc4f6
--- /dev/null
+++ b/ciphers/SimpleSubstitutionCipher.java
@@ -0,0 +1,97 @@
+package ciphers;
+
+import java.util.*;
+
+/**
+ *
+ * The simple substitution cipher is a cipher that has been in use for many hundreds of years 
+ * (an excellent history is given in Simon Singhs 'the Code Book'). 
+ * It basically consists of substituting every plaintext character for a different ciphertext character. 
+ * It differs from the Caesar cipher in that the cipher alphabet is not simply the alphabet shifted,
+ * it is completely jumbled.
+ * 
+ * @author Hassan Elseoudy
+ */
+
+public class SimpleSubstitutionCipher {
+
+    /**
+     * Encrypt text by replacing each element with its opposite character.
+     *
+     * @param message
+     * @param cipherSmall
+     * @return Encrypted message
+     */
+    public static String encode(String message, String cipherSmall) {
+        String encoded = "";
+
+        // This map is used to encode
+        Map<Character,Character> cipherMap = new HashMap<Character,Character>();
+
+        char beginSmallLetter = 'a';
+        char beginCapitalLetter = 'A';
+
+        cipherSmall = cipherSmall.toLowerCase();
+        String cipherCapital = cipherSmall.toUpperCase();
+
+        // To handle Small and Capital letters
+        for(int i = 0; i < cipherSmall.length(); i++){
+            cipherMap.put(beginSmallLetter++,cipherSmall.charAt(i));
+            cipherMap.put(beginCapitalLetter++,cipherCapital.charAt(i));
+        }
+
+        for(int i = 0; i < message.length(); i++){
+            if(Character.isAlphabetic(message.charAt(i)))
+                encoded += cipherMap.get(message.charAt(i));
+            else
+                encoded += message.charAt(i);
+        }
+
+        return encoded;
+    }
+
+    /**
+     * Decrypt message by replacing each element with its opposite character in cipher.
+     *
+     * @param encryptedMessage
+     * @param cipherSmall
+     * @return message
+     */
+    public static String decode(String encryptedMessage, String cipherSmall) {
+        String decoded = "";
+
+
+        Map<Character,Character> cipherMap = new HashMap<Character,Character>();
+
+        char beginSmallLetter = 'a';
+        char beginCapitalLetter = 'A';
+
+        cipherSmall = cipherSmall.toLowerCase();
+        String cipherCapital = cipherSmall.toUpperCase();
+
+        for(int i = 0; i < cipherSmall.length(); i++){
+            cipherMap.put(cipherSmall.charAt(i),beginSmallLetter++);
+            cipherMap.put(cipherCapital.charAt(i),beginCapitalLetter++);
+        }
+
+        for(int i = 0; i < encryptedMessage.length(); i++){
+            if(Character.isAlphabetic(encryptedMessage.charAt(i)))
+                decoded += cipherMap.get(encryptedMessage.charAt(i));
+            else
+                decoded += encryptedMessage.charAt(i);
+        }
+
+        return decoded;
+    }
+
+    /**
+     *
+     * TODO remove main and make JUnit Testing
+     */
+    public static void main(String[] args) {
+        String a = encode("defend the east wall of the castle","phqgiumeaylnofdxjkrcvstzwb");
+        String b = decode(a,"phqgiumeaylnofdxjkrcvstzwb");
+        System.out.println(b);
+    }
+
+}
\ No newline at end of file

From e21d0efd6ae46bf744eb4d4164a4ca2c5e376d7d Mon Sep 17 00:00:00 2001
From: nikhil kala <nikhilkala8@gmail.com>
Date: Wed, 29 Jan 2020 01:46:27 +0530
Subject: [PATCH 2/2] Update SimpleSubstitutionCipher.java

---
 ciphers/SimpleSubstitutionCipher.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ciphers/SimpleSubstitutionCipher.java b/ciphers/SimpleSubstitutionCipher.java
index 983bc4f6..d9bae4f0 100644
--- a/ciphers/SimpleSubstitutionCipher.java
+++ b/ciphers/SimpleSubstitutionCipher.java
@@ -94,4 +94,4 @@ public class SimpleSubstitutionCipher {
         System.out.println(b);
     }
 
-}
\ No newline at end of file
+}