##Intro. String encryption is a protection method to convert Readable string to Unreadable String.
##Let's Start. First of all we have to Select the application that we want to Obfuscate it.
ModuleDef md = ModuleDefMD.Load(@"AppPath"); //replace AppPath with your Application Path you want to Obfuscate it.Then we have to load the Types from the Module.
foreach(TypeDef type in md.Types)
{
}after we loaded the Types from module, now we have to get the methods from the type.
foreach(MethodDef method in type.Methods)
{
}After we loaded the Methods from type, now we need to get the Instructions for method and check if there's any String (String OpCode = Ldstr). But we should check if the method body isn't Null.
if (method.Body == null) continue;Now we are going to get the instructions from method.
for(int i = 0; i < method.Body.Instructions.Count; i++)
{
}after getting the instructions from method, and check it if its null or no. now we have to check if the instruction is String
if (method.Body.Instructions[i].OpCode == OpCodes.Ldstr)
{
}I will use Base64 for Encrypt the String and UTF8 for Encoding.
String oldString = method.Body.Instructions[i].Operand.ToString(); //Original String.
String newString = Convert.ToBase64String(UTF8Encoding.UTF8.GetBytes(oldString)); //Encrypted String by Base64Now we have to Inject the Decrypt Instructions
###Decrypt Instructions
To Dnlib Inject
method.Body.Instructions[i].OpCode = OpCodes.Nop; //Change the Opcode for the Original Instruction
method.Body.Instructions.Insert(i + 1, new Instruction(OpCodes.Call, md.Import(typeof(System.Text.Encoding).GetMethod("get_UTF8", new Type[] { })))); //get Method (get_UTF8) from Type (System.Text.Encoding).
method.Body.Instructions.Insert(i + 2, new Instruction(OpCodes.Ldstr, newString)); //add the Encrypted String
method.Body.Instructions.Insert(i + 3, new Instruction(OpCodes.Call, md.Import(typeof(System.Convert).GetMethod("FromBase64String", new Type[] { typeof(string) })))); //get Method (FromBase64String) from Type (System.Convert), and arguments for method we will get it using "new Type[] { typeof(string) }"
method.Body.Instructions.Insert(i + 4, new Instruction(OpCodes.Callvirt, md.Import(typeof(System.Text.Encoding).GetMethod("GetString", new Type[] { typeof(byte[]) }))));
i += 4; //skip the Instructions that we have just added.Now we're almost done, now we only need to Write the obfuscated module.
md.Write("ObfuscatedApp.exe");Done, Enjoy :)).
###the code should be like this
ModuleDef md = ModuleDefMD.Load(@"AppPath");
foreach(TypeDef type in md.Types)
{
foreach (MethodDef method in type.Methods)
{
if (method.Body == null) continue;
for(int i = 0; i < method.Body.Instructions.Count(); i++)
{
if (method.Body.Instructions[i].OpCode == OpCodes.Ldstr)
{
//Encoding.UTF8.GetString(Convert.FromBase64String(""));
String oldString = method.Body.Instructions[i].Operand.ToString(); //Original String.
String newString = Convert.ToBase64String(UTF8Encoding.UTF8.GetBytes(oldString)); //Encrypted String by Base64
method.Body.Instructions[i].OpCode = OpCodes.Nop; //Change the Opcode for the Original Instruction
method.Body.Instructions.Insert(i + 1, new Instruction(OpCodes.Call, md.Import(typeof(System.Text.Encoding).GetMethod("get_UTF8", new Type[] { })))); //get Method (get_UTF8) from Type (System.Text.Encoding).
method.Body.Instructions.Insert(i + 2, new Instruction(OpCodes.Ldstr, newString)); //add the Encrypted String
method.Body.Instructions.Insert(i + 3, new Instruction(OpCodes.Call, md.Import(typeof(System.Convert).GetMethod("FromBase64String", new Type[] { typeof(string) })))); //get Method (FromBase64String) from Type (System.Convert), and arguments for method we will get it using "new Type[] { typeof(string) }"
method.Body.Instructions.Insert(i + 4, new Instruction(OpCodes.Callvirt, md.Import(typeof(System.Text.Encoding).GetMethod("GetString", new Type[] { typeof(byte[]) }))));
i += 4; //skip the Instructions that we have just added.
}
}
}
}
md.Write("ObfuscatedApp.exe");
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