Initial commit

.gitignore

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+.vs/
+bin/
+obj/

eAmuseCore/Crypto/RC4.cs

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+using System.Collections.Generic;
+using System.Security.Cryptography;
+using System.Linq;
+using System;
+
+namespace eAmuseCore.Crypto
+{
+    public static class RC4
+    {
+        private static readonly byte[] konamiCode = 
+            new byte[]{ 105, 215, 70, 39, 217, 133, 238, 33, 135,
+                        22, 21, 112, 208, 141, 147, 177, 36, 85,
+                        3, 91, 109, 240, 216, 32, 93, 245 };
+
+        public static IEnumerable<byte> ApplyEAmuseInfo(string info, IEnumerable<byte> data)
+        {
+            if (!info.StartsWith("1-") || info.Count(c => c == '-') != 3 || info.Length != 15)
+                throw new ArgumentException("Unknown E-Amuse-Info format.", "info");
+            info = info.Substring(2).Replace("-", "");
+            byte[] key = Enumerable.Range(0, info.Length / 2).Select(i => Convert.ToByte(info.Substring(i * 2, 2))).ToArray();
+            return ApplyEAmuse(key, data);
+        }
+
+        public static IEnumerable<byte> ApplyEAmuse(byte[] key, IEnumerable<byte> data)
+        {
+            if (key.Length != 6)
+                throw new ArgumentException("Key length has to be exactly 6 bytes.", "key");
+
+            using (MD5 md5 = MD5.Create())
+            {
+                byte[] realKey = md5.ComputeHash(key.Concat(konamiCode).ToArray());
+                return Apply(realKey, data);
+            }
+        }
+
+        public static IEnumerable<byte> Apply(byte[] key, IEnumerable<byte> data)
+        {
+            return EncryptOutput(key, data);
+        }
+
+        private static byte[] EncryptInitalize(byte[] key)
+        {
+            byte[] s = Enumerable.Range(0, 256).Select(i => (byte)i).ToArray();
+
+            for (uint i = 0, j = 0; i < 256; i++)
+            {
+                j = (j + key[i % key.Length] + s[i]) & 255;
+                Swap(s, i, j);
+            }
+
+            return s;
+        }
+
+        private static IEnumerable<byte> EncryptOutput(byte[] key, IEnumerable<byte> data)
+        {
+            byte[] s = EncryptInitalize(key);
+
+            uint i = 0;
+            uint j = 0;
+
+            return data.Select(b =>
+            {
+                i = (i + 1) & 255;
+                j = (j + s[i]) & 255;
+
+                Swap(s, i, j);
+
+                return (byte)(b ^ s[(s[i] + s[j]) & 255]);
+            });
+        }
+
+        private static void Swap(byte[] s, uint i, uint j)
+        {
+            byte c = s[i];
+
+            s[i] = s[j];
+            s[j] = c;
+        }
+    }
+}

eAmuseCore/eAmuseCore.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="System.Security.Cryptography.Algorithms" Version="4.3.1" />
+  </ItemGroup>
+
+</Project>

eAmuseSharp.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.28803.156
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "eAmuseCore", "eAmuseCore\eAmuseCore.csproj", "{016891F1-140A-4DDF-B036-BDFAF98D4414}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "eAmuseTest", "eAmuseTest\eAmuseTest.csproj", "{0BB29C0C-2ED9-4D1A-BD03-908BEAAD463C}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{016891F1-140A-4DDF-B036-BDFAF98D4414}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{016891F1-140A-4DDF-B036-BDFAF98D4414}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{016891F1-140A-4DDF-B036-BDFAF98D4414}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{016891F1-140A-4DDF-B036-BDFAF98D4414}.Release|Any CPU.Build.0 = Release|Any CPU
+		{0BB29C0C-2ED9-4D1A-BD03-908BEAAD463C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{0BB29C0C-2ED9-4D1A-BD03-908BEAAD463C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{0BB29C0C-2ED9-4D1A-BD03-908BEAAD463C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{0BB29C0C-2ED9-4D1A-BD03-908BEAAD463C}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {5060C3AB-087C-41A8-96FF-CFB9AA8011B7}
+	EndGlobalSection
+EndGlobal

eAmuseTest/Program.cs

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+using System;
+
+namespace eAmuseTest
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine("Hello World!");
+        }
+    }
+}

eAmuseTest/eAmuseTest.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp2.2</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\eAmuseCore\eAmuseCore.csproj" />
+  </ItemGroup>
+
+</Project>