From 5226b7c62d5b8eb9d27f64fd88c58c1522398a65 Mon Sep 17 00:00:00 2001
From: Sebastian Walther <github.dev@sebastian-walther.de>
Date: Thu, 7 Mar 2024 22:46:39 +0100
Subject: [PATCH] Clear Memory

Resolves: No entry
---
 src/Cryptography/ShamirsSecretSharing.cs   |  5 +++
 src/Cryptography/ShamirsSecretSharing`3.cs | 36 +++++++++++++++++-----
 src/Cryptography/SharedSeparator.cs        |  4 +--
 src/Math/Calculator.cs                     |  2 +-
 src/SecretSharingDotNet.csproj             |  8 +++++
 5 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/src/Cryptography/ShamirsSecretSharing.cs b/src/Cryptography/ShamirsSecretSharing.cs
index e00ff77..86bcc7e 100644
--- a/src/Cryptography/ShamirsSecretSharing.cs
+++ b/src/Cryptography/ShamirsSecretSharing.cs
@@ -5,6 +5,11 @@ namespace SecretSharingDotNet.Cryptography;
 /// </summary>
 public abstract class ShamirsSecretSharing
 {
+    /// <summary>
+    /// The minimum number of shares required to reconstruct the secret
+    /// </summary>
+    protected const int MinimumShareLimit = 2;
+
     /// <summary>
     /// Saves the known security levels (Mersenne prime exponents)
     /// </summary>
diff --git a/src/Cryptography/ShamirsSecretSharing`3.cs b/src/Cryptography/ShamirsSecretSharing`3.cs
index 2f5531c..0ade8c4 100644
--- a/src/Cryptography/ShamirsSecretSharing`3.cs
+++ b/src/Cryptography/ShamirsSecretSharing`3.cs
@@ -70,7 +70,7 @@ public class ShamirsSecretSharing<TNumber, TExtendedGcdAlgorithm, TExtendedGcdRe
     public ShamirsSecretSharing(TExtendedGcdAlgorithm extendedGcd)
     {
         this.extendedGcd = extendedGcd ?? throw new ArgumentNullException(nameof(extendedGcd));
-        this.SecurityLevel = 13;
+        this.SecurityLevel = SecurityLevels[0];
     }
 
     /// <summary>
@@ -84,7 +84,7 @@ public int SecurityLevel
 
         set
         {
-            if (value < 13)
+            if (value < SecurityLevels[0])
             {
                 throw new ArgumentOutOfRangeException(nameof(value), value, ErrorMessages.MinimumSecurityLevelExceeded);
             }
@@ -128,7 +128,7 @@ public Shares<TNumber> MakeShares(TNumber numberOfMinimumShares, TNumber numberO
 
         int min = ((Calculator<TNumber>)numberOfMinimumShares).ToInt32();
         int max = ((Calculator<TNumber>)numberOfShares).ToInt32();
-        if (min < 2)
+        if (min < MinimumShareLimit)
         {
             throw new ArgumentOutOfRangeException(nameof(numberOfMinimumShares), numberOfMinimumShares, ErrorMessages.MinNumberOfSharesLowerThanTwo);
         }
@@ -187,7 +187,7 @@ public Shares<TNumber> MakeShares(TNumber numberOfMinimumShares, TNumber numberO
     {
         int min = ((Calculator<TNumber>)numberOfMinimumShares).ToInt32();
         int max = ((Calculator<TNumber>)numberOfShares).ToInt32();
-        if (min < 2)
+        if (min < MinimumShareLimit)
         {
             throw new ArgumentOutOfRangeException(nameof(numberOfMinimumShares), numberOfMinimumShares, ErrorMessages.MinNumberOfSharesLowerThanTwo);
         }
@@ -215,20 +215,40 @@ public Shares<TNumber> MakeShares(TNumber numberOfMinimumShares, TNumber numberO
     /// </summary>
     /// <param name="numberOfMinimumShares">Minimum number of shared secrets for reconstruction</param>
     /// <returns></returns>
+#if NET6_0_OR_GREATER
+    private unsafe Calculator<TNumber>[] CreatePolynomial(int numberOfMinimumShares)
+#else
     private Calculator<TNumber>[] CreatePolynomial(int numberOfMinimumShares)
+#endif
     {
         var polynomial = new Calculator<TNumber>[numberOfMinimumShares];
         polynomial[0] = Calculator<TNumber>.Zero;
         byte[] randomNumber = new byte[this.mersennePrime.ByteCount];
-        using (var rng = RandomNumberGenerator.Create())
+#if NET6_0_OR_GREATER
+        fixed (byte* pointer = randomNumber)
         {
+            var span = new Span<byte>(pointer, this.mersennePrime.ByteCount);
+            using var rng = RandomNumberGenerator.Create();
             for (int i = 1; i < numberOfMinimumShares; i++)
             {
-                rng.GetBytes(randomNumber);
-                polynomial[i] = (Calculator.Create(randomNumber, typeof(TNumber)) as Calculator<TNumber>)?.Abs() % this.mersennePrime;
+                rng.GetBytes(span);
+                polynomial[i] = (Calculator.Create(randomNumber, typeof(TNumber)) as Calculator<TNumber>)?.Abs() %
+                                this.mersennePrime;
             }
-        }
 
+            span.Clear();
+        }
+#else
+         using var rng = RandomNumberGenerator.Create();
+         for (int i = 1; i < numberOfMinimumShares; i++)
+         {
+             rng.GetBytes(randomNumber);
+             polynomial[i] = (Calculator.Create(randomNumber, typeof(TNumber)) as Calculator<TNumber>)?.Abs() %
+                             this.mersennePrime;
+         }
+
+         Array.Clear(randomNumber, 0, randomNumber.Length);
+#endif
         return polynomial;
     }
 
diff --git a/src/Cryptography/SharedSeparator.cs b/src/Cryptography/SharedSeparator.cs
index e86345d..94588ec 100644
--- a/src/Cryptography/SharedSeparator.cs
+++ b/src/Cryptography/SharedSeparator.cs
@@ -41,5 +41,5 @@ internal static class SharedSeparator
     /// <summary>
     /// Separator array for <see cref="string.Split(char[])"/> method usage to avoid allocation of a new array.
     /// </summary>
-    internal static readonly char[] CoordinateSeparatorArray = { CoordinateSeparator };
-}
\ No newline at end of file
+    internal static readonly char[] CoordinateSeparatorArray = [CoordinateSeparator];
+}
diff --git a/src/Math/Calculator.cs b/src/Math/Calculator.cs
index 840fbeb..9dbf0e3 100644
--- a/src/Math/Calculator.cs
+++ b/src/Math/Calculator.cs
@@ -117,7 +117,7 @@ protected static Dictionary<Type, Func<TParameter, TCalculator>> GetDerivedCtors
         var parameterExpression = Expression.Parameter(paramType);
         foreach (var childType in ChildTypes)
         {
-            var ctorInfo = childType.Value.GetConstructor(new[] {paramType});
+            var ctorInfo = childType.Value.GetConstructor([paramType]);
             if (ctorInfo == null)
             {
                 continue;
diff --git a/src/SecretSharingDotNet.csproj b/src/SecretSharingDotNet.csproj
index a196c0b..db83f4c 100644
--- a/src/SecretSharingDotNet.csproj
+++ b/src/SecretSharingDotNet.csproj
@@ -33,6 +33,14 @@
         <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
     </PropertyGroup>
 
+    <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
+      <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    </PropertyGroup>
+
+    <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
+      <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    </PropertyGroup>
+
     <ItemGroup>
         <EmbeddedResource Update="Resources\ErrorMessages.resx">
             <Generator>ResXFileCodeGenerator</Generator>