From 1aeb224be8cdc75d71627107e5d195277755c3cc Mon Sep 17 00:00:00 2001
From: Kevin Froman <beardog@mailbox.org>
Date: Mon, 25 May 2020 00:05:49 -0500
Subject: [PATCH] added entropy calculator

---
 cli/ui/interfaces/encrypt.cs                  |  3 ++
 tests/kdf/symmetricKDFTest.cs                 |  0
 tests/testEntropy.cs                          | 31 ++++++++++++++++
 treasurechest/EntropyCal.cs                   | 37 +++++++++++++++++++
 .../key-derivation/deriveSymmetric.cs         | 26 +++++++++++++
 .../symmetric-crypto/encryptwithpassphrase.cs | 19 ++++++++++
 6 files changed, 116 insertions(+)
 create mode 100644 tests/kdf/symmetricKDFTest.cs
 create mode 100644 tests/testEntropy.cs
 create mode 100644 treasurechest/EntropyCal.cs
 create mode 100644 treasurechest/chestcrypto/key-derivation/deriveSymmetric.cs
 create mode 100644 treasurechest/chestcrypto/symmetric-crypto/encryptwithpassphrase.cs

diff --git a/cli/ui/interfaces/encrypt.cs b/cli/ui/interfaces/encrypt.cs
index f9e2f1c..a58c199 100644
--- a/cli/ui/interfaces/encrypt.cs
+++ b/cli/ui/interfaces/encrypt.cs
@@ -2,6 +2,7 @@ using System.IO;
 using System;
 using treasurechest.STDIOWrapper;
 using getpass;
+using ShannonEntropyCal;
 
 namespace treasurechestCLI{
 
@@ -11,6 +12,7 @@ namespace treasurechestCLI{
             int counter = 1;
             string message;
             string passphrase;
+            string encrypted;
 
             translations.Strings strings = new translations.Strings();
 
@@ -52,6 +54,7 @@ namespace treasurechestCLI{
                         continue;
                     }
                     passphrase = GetPass.getPass(strings.PASSPHRASE);
+                    encrypted = 
                 }
                 else if (choice == encryptMenuOptions.Length){
                     break;
diff --git a/tests/kdf/symmetricKDFTest.cs b/tests/kdf/symmetricKDFTest.cs
new file mode 100644
index 0000000..e69de29
diff --git a/tests/testEntropy.cs b/tests/testEntropy.cs
new file mode 100644
index 0000000..6acb391
--- /dev/null
+++ b/tests/testEntropy.cs
@@ -0,0 +1,31 @@
+using NUnit.Framework;
+using ShannonEntropyCal;
+using System;
+
+namespace entropytests
+{
+    public class Tests
+    {
+        [SetUp]
+        public void Setup()
+        {
+        }
+
+        [Test]
+        public void TestShannonEntropyLow()
+        {
+            string low = "abc123";
+            if (EntropyCal.EntropyValue(low) > 3.0){
+                Assert.Fail();
+            }
+        }
+
+        [Test]
+        public void TestShannonEntropyHigh()
+        {
+            string high = "ý¼¸²>æ{£¤@TçKA¥£åKPk.rPoSo}fÑú½§rêÆÀðke(9/¹©ÔRqTãîý`Çóè°T²þµ)ÁÄÒÙr7éijÈ·Ñø{.8'ü*=Å.ôþSø&ÏßP9D}\"û+îÏæ¼aZ-'ûÐмÊZh5³ÒD®/YÙ¤(a·]Ðf";
+            Assert.IsTrue(EntropyCal.EntropyValue(high) > 6.3);
+        }
+
+    }
+}
\ No newline at end of file
diff --git a/treasurechest/EntropyCal.cs b/treasurechest/EntropyCal.cs
new file mode 100644
index 0000000..3887112
--- /dev/null
+++ b/treasurechest/EntropyCal.cs
@@ -0,0 +1,37 @@
+// Taken from https://github.com/Kaynn-Cahya/Shannon-Entropy with no license given.
+// Since this was published on nuget, i am assuming the author is ok with it being used in open source
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+// Test: testEntropy.cs
+namespace ShannonEntropyCal
+{
+    public class EntropyCal
+    {
+
+        public static double EntropyValue(string message)
+        {
+            Dictionary<char, int> K = message.GroupBy(c => c).ToDictionary(g => g.Key, g => g.Count());
+            double EntropyValue = 0;
+            foreach (var character in K)
+            {
+                double PR = character.Value / (double) message.Length;
+                EntropyValue -= PR * Math.Log(PR, 2);
+            }
+            return EntropyValue;
+        }
+
+        public static double EntropyBits(string message)
+        {
+            Dictionary<char, int> K = message.GroupBy(c => c).ToDictionary(g => g.Key, g => g.Count());
+            double EntropyValue = 0;
+            foreach (var character in K)
+            {
+                double PR = character.Value / (double) message.Length;
+                EntropyValue -= PR * Math.Log(PR, 2);
+            }
+            return Math.Ceiling(EntropyValue) * message.Length;
+        }
+    }
+}
diff --git a/treasurechest/chestcrypto/key-derivation/deriveSymmetric.cs b/treasurechest/chestcrypto/key-derivation/deriveSymmetric.cs
new file mode 100644
index 0000000..1ae637c
--- /dev/null
+++ b/treasurechest/chestcrypto/key-derivation/deriveSymmetric.cs
@@ -0,0 +1,26 @@
+
+using System.Text;
+using Sodium;
+
+namespace chestcrypto{
+
+    namespace kdf{
+        public class DeterministicSymmetricKey{
+            // Test
+            public static byte[] generate(string passphrase, bool extraSensitive=false){
+                var nonce = SecretBox.GenerateNonce();
+                int strength = 2;
+                if (extraSensitive){
+                    strength = 3;
+                }
+                return PasswordHash.ArgonHashBinary(Encoding.UTF8.GetBytes(passphrase), // Passphrase converted to bytes
+                                            PasswordHash.ArgonGenerateSalt(), // Salt
+                                            strength, strength,
+                                            32);
+            }
+
+        }
+
+    }
+
+}
diff --git a/treasurechest/chestcrypto/symmetric-crypto/encryptwithpassphrase.cs b/treasurechest/chestcrypto/symmetric-crypto/encryptwithpassphrase.cs
new file mode 100644
index 0000000..9b912ff
--- /dev/null
+++ b/treasurechest/chestcrypto/symmetric-crypto/encryptwithpassphrase.cs
@@ -0,0 +1,19 @@
+using Sodium;
+using System;
+using chestcrypto.kdf;
+namespace treasurechest{
+
+    namespace symmetric{
+
+        public class EncryptWithPassphrase{
+            /* Class name is somewhat misleading as we actually derive a key from a string pass and use the key for secret key crypto*/
+            public static byte[] encrypt(byte[] data, string passphrase, bool extraSensitive = false){
+                byte[] key = DeterministicSymmetricKey.generate(passphrase, extraSensitive);
+                return SecretBox.Create(data, SecretBox.GenerateNonce(), key);
+            }
+
+        }
+
+    }
+
+}
\ No newline at end of file