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feature: randomize compressor feedback + library-seed constants (#69) #100

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feature: randomize compressor feedback + library-seed constants (#69) #100

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7d747ca
feature: randomize compressor feedback constant per run (#69)
Jul 4, 2026
322c518
feature: randomize compressor library-seed hash constants per run (#69)
Jul 4, 2026
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33 changes: 30 additions & 3 deletions Confuser.Protections/Compress/Compressor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -160,9 +160,9 @@ void PackModules(ConfuserContext context, CompressorContext compCtx, ModuleDef s
for (int i = 0; i < name.Length; i++)
name[i] *= key[i + 4];

uint state = 0x6fff61;
uint state = compCtx.LcgInit;
foreach (byte chr in name)
state = state * 0x5e3f1f + chr;
state = state * compCtx.LcgMultiplier + chr;
byte[] encrypted = compCtx.Encrypt(comp, entry.Value, state, progress => {
progress = (progress + moduleIndex) / modules.Count;
context.ProgressReporter.Progress((int)(progress * 10000), 10000);
Expand Down Expand Up @@ -242,6 +242,17 @@ void InjectStub(ConfuserContext context, CompressorContext compCtx, ProtectionPa
new MemberRefUser(stubModule, ".ctor", ctorSig, attrType)));
}

// Randomize the encryption feedback constant (baked-in 0x3ddb2819 fingerprints the
// stub). Any value works since it is purely additive; the same value is injected into
// the runtime Decrypt method below so encrypt/decrypt stay in sync.
compCtx.Feedback = random.NextUInt32();

// Randomize the rolling-hash used to derive each library's seed from its name
// (baked-in 0x6fff61 / 0x5e3f1f). The multiplier is kept odd for good distribution.
// The same values are injected into the runtime Resolve method below.
compCtx.LcgInit = random.NextUInt32();
compCtx.LcgMultiplier = random.NextUInt32() | 1;

uint seed = random.NextUInt32();
compCtx.OriginModule = context.OutputModules[compCtx.ModuleIndex];

Expand All @@ -263,7 +274,11 @@ void InjectStub(ConfuserContext context, CompressorContext compCtx, ProtectionPa
List<Instruction> instrs = decrypter.Body.Instructions.ToList();
for (int i = 0; i < instrs.Count; i++) {
Instruction instr = instrs[i];
if (instr.OpCode == OpCodes.Call) {
if (instr.OpCode == OpCodes.Ldc_I4 && (int)instr.Operand == 0x3ddb2819) {
// Sync the runtime feedback constant with the value used during encryption.
instr.Operand = (int)compCtx.Feedback;
}
else if (instr.OpCode == OpCodes.Call) {
var method = (IMethod)instr.Operand;
if (method.DeclaringType.Name == "Mutation" &&
method.Name == "Crypt") {
Expand All @@ -286,6 +301,18 @@ void InjectStub(ConfuserContext context, CompressorContext compCtx, ProtectionPa
foreach (Instruction instr in instrs)
decrypter.Body.Instructions.Add(instr);

// Resolve — sync the runtime rolling-hash constants with the values used when
// deriving each library's seed from its name (see PackModules).
MethodDef resolver = defs.OfType<MethodDef>().Single(method => method.Name == "Resolve");
foreach (Instruction instr in resolver.Body.Instructions) {
if (instr.OpCode != OpCodes.Ldc_I4)
continue;
if ((int)instr.Operand == 0x6fff61)
instr.Operand = (int)compCtx.LcgInit;
else if ((int)instr.Operand == 0x5e3f1f)
instr.Operand = (int)compCtx.LcgMultiplier;
}

// Pack modules
PackModules(context, compCtx, stubModule, comp, random);
}
Expand Down
5 changes: 4 additions & 1 deletion Confuser.Protections/Compress/CompressorContext.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,9 @@ internal class CompressorContext {
public byte[] OriginModule;
public ModuleDef OriginModuleDef;
public bool CompatMode;
public uint Feedback;
public uint LcgInit;
public uint LcgMultiplier;

public byte[] Encrypt(ICompressionService compress, byte[] data, uint seed, Action<double> progressFunc) {
data = (byte[])data.Clone();
Expand Down Expand Up @@ -46,7 +49,7 @@ public byte[] Encrypt(ICompressionService compress, byte[] data, uint seed, Acti
for (int i = 0; i < data.Length; i += 4) {
var datum = (uint)(data[i + 0] | (data[i + 1] << 8) | (data[i + 2] << 16) | (data[i + 3] << 24));
uint encrypted = datum ^ key[keyIndex & 0xf];
key[keyIndex & 0xf] = (key[keyIndex & 0xf] ^ datum) + 0x3ddb2819;
key[keyIndex & 0xf] = (key[keyIndex & 0xf] ^ datum) + Feedback;
encryptedData[i + 0] = (byte)(encrypted >> 0);
encryptedData[i + 1] = (byte)(encrypted >> 8);
encryptedData[i + 2] = (byte)(encrypted >> 16);
Expand Down