Implemented random pin generator, removed unecessary comments

FallIntoOblivion/src/fallintooblivion/Helpers.java

-/*
- * To change this license header, choose License Headers in Project Properties.
- * To change this template file, choose Tools | Templates
- * and open the template in the editor.
- */
 package fallintooblivion;
 
 import javax.crypto.Cipher;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
+import java.security.SecureRandom;
 import java.util.Arrays;
 
 
@@ -286,14 +282,20 @@ public class Helpers {
 
                 String outFile = "Fall_Into_Oblivion/Trashed/" + fileName + "/" + fileName;
 
-                // TEMPORARY debugging purposes only
-                // Create the hash of the pin 0000
+
                 // So far we were only able to use 16 Byte key
                 // 24 Byte or 32 Byte will say Invalid Key Size, even though it's a valid key size
-                // TODO: Randomize 3 or 4 digit pin without printing it to the user
-                String pinHASH = SHA256.calculateStringMAC("0000");
+                RandomString pinGenerator = new RandomString(4, new SecureRandom(), RandomString.Symbols.digits);
+                String genPin = pinGenerator.nextString();
+                String pinHASH = SHA256.calculateStringMAC(genPin);
                 pinHASH = pinHASH.subSequence(0, 16).toString();
 
+                // System.out.println(genPin); // Uncomment this line to view the generated pin
+
+                // Uncomment the two lines below to generate the key to the pin 0000
+                // String pinHASH = SHA256.calculateStringMAC("0000");
+                // pinHASH = pinHASH.subSequence(0, 16).toString();
+
                 // Encrypt the file using the defined cypher type, it defaults to AES-CBC
                 switch (cypher) {
                     case "aes_cbc":

FallIntoOblivion/src/fallintooblivion/RandomString.java

+package fallintooblivion;
+
+import java.security.SecureRandom;
+import java.util.Locale;
+import java.util.Objects;
+import java.util.Random;
+
+public class RandomString {
+
+    /**
+     * Generate a random string.
+     */
+    public String nextString() {
+        for (int idx = 0; idx < buf.length; ++idx)
+            buf[idx] = symbols[random.nextInt(symbols.length)];
+        return new String(buf);
+    }
+
+    public enum Symbols {
+        uppercase,
+        lowercase,
+        digits,
+        alphanumeric,
+        upperlowercase
+    }
+
+    public static final String upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    public static final String lower = upper.toLowerCase(Locale.ROOT);
+
+    public static final String digits = "0123456789";
+
+    public static final String alphanum = upper + lower + digits;
+
+    private final Random random;
+
+    private final char[] symbols;
+
+    private final char[] buf;
+
+    public RandomString(int length, Random random, String symbols) {
+        if (length < 1) throw new IllegalArgumentException();
+        if (symbols.length() < 2) throw new IllegalArgumentException();
+        this.random = Objects.requireNonNull(random);
+        this.symbols = symbols.toCharArray();
+        this.buf = new char[length];
+    }
+
+    public RandomString(int length, Random random, Symbols symbols) {
+        switch (symbols) {
+            case digits:
+                this.random = Objects.requireNonNull(random);
+                this.symbols = digits.toCharArray();
+                this.buf = new char[length];
+                break;
+            case lowercase:
+                this.random = Objects.requireNonNull(random);
+                this.symbols = lower.toCharArray();
+                this.buf = new char[length];
+                break;
+            case uppercase:
+                this.random = Objects.requireNonNull(random);
+                this.symbols = upper.toCharArray();
+                this.buf = new char[length];
+                break;
+            case alphanumeric:
+                this.random = Objects.requireNonNull(random);
+                this.symbols = alphanum.toCharArray();
+                this.buf = new char[length];
+                break;
+            case upperlowercase:
+                String alphabet = upper + lower;
+                this.random = Objects.requireNonNull(random);
+                this.symbols = alphabet.toCharArray();
+                this.buf = new char[length];
+                break;
+            default:
+                this.random = Objects.requireNonNull(random);
+                this.symbols = alphanum.toCharArray();
+                this.buf = new char[length];
+                break;
+        }
+    }
+
+    /**
+     * Create an alphanumeric string generator.
+     */
+    public RandomString(int length, Random random) {
+        this(length, random, alphanum);
+    }
+
+    /**
+     * Create an alphanumeric strings from a secure generator.
+     */
+    public RandomString(int length) {
+        this(length, new SecureRandom());
+    }
+
+    /**
+     * Create session identifiers.
+     */
+    public RandomString() {
+        this(21);
+    }
+
+}
\ No newline at end of file