From 5677d94e6aa22c657f8440d6dc4beb38f28509e8 Mon Sep 17 00:00:00 2001
From: Leonetienne <leon@etiennes.de>
Date: Sun, 22 May 2022 20:13:41 +0200
Subject: [PATCH] Improved security

---
 GCryptLib/include/GCrypt/Config.h  |  2 +-
 GCryptLib/include/GCrypt/GCipher.h |  3 +++
 GCryptLib/src/Feistel.cpp          | 15 +++++++--------
 GCryptLib/src/GCipher.cpp          |  6 ++++++
 GCryptLib/src/GHash.cpp            |  7 +++++--
 5 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/GCryptLib/include/GCrypt/Config.h b/GCryptLib/include/GCrypt/Config.h
index c5ec236..dd56656 100644
--- a/GCryptLib/include/GCrypt/Config.h
+++ b/GCryptLib/include/GCrypt/Config.h
@@ -8,7 +8,7 @@ namespace Leonetienne::GCrypt {
   constexpr std::size_t BLOCK_SIZE = 512;
 
   // MUST BE > 2
-  constexpr std::size_t N_ROUNDS = 64;
+  constexpr std::size_t N_ROUNDS = 400;
 }
 
 #endif
diff --git a/GCryptLib/include/GCrypt/GCipher.h b/GCryptLib/include/GCrypt/GCipher.h
index f17a277..6050233 100644
--- a/GCryptLib/include/GCrypt/GCipher.h
+++ b/GCryptLib/include/GCrypt/GCipher.h
@@ -25,6 +25,9 @@ namespace Leonetienne::GCrypt {
     //! Will digest a data block, and return it
     Block Digest(const Block& input);
 
+    //! Will update the base key used
+    void SetKey(const Key& key);
+
     void operator=(const GCipher& other);
 
   private:
diff --git a/GCryptLib/src/Feistel.cpp b/GCryptLib/src/Feistel.cpp
index ce69306..9ac75da 100644
--- a/GCryptLib/src/Feistel.cpp
+++ b/GCryptLib/src/Feistel.cpp
@@ -54,12 +54,13 @@ namespace Leonetienne::GCrypt {
 
     // Block has finished de*ciphering.
     // Let's generate a new set of round keys.
-    GenerateRoundKeys((Block)roundKeys.back());
+    GenerateRoundKeys((Key)roundKeys.back());
 
     return FeistelCombine(r, l);
   }
 
   Halfblock Feistel::F(Halfblock m, const Key& key) {
+
     // Made-up F function
 
     // Expand to full bitwidth
@@ -74,15 +75,13 @@ namespace Leonetienne::GCrypt {
     // Non-linearly apply subsitution boxes
     std::stringstream ss;
     const std::string m_str = m_expanded.to_string();
-
     for (std::size_t i = 0; i < BLOCK_SIZE; i += 4) {
       ss << SBox(m_str.substr(i, 4));
     }
-
     m_expanded = Block(ss.str());
 
-    // Return the compressed version
-    return CompressionFunction(m_expanded);
+    // Return the compressed version, shifted by 3
+    return Shiftl(CompressionFunction(m_expanded), 3);
   }
 
   std::pair<Halfblock, Halfblock> Feistel::FeistelSplit(const Block& block) {
@@ -124,13 +123,13 @@ namespace Leonetienne::GCrypt {
     std::unordered_map<std::string, std::string> compressionMap;
     compressionMap["0000"] = "10";
     compressionMap["0001"] = "01";
-    compressionMap["0010"] = "10";
+    compressionMap["0010"] = "11";
     compressionMap["0011"] = "10";
     compressionMap["0100"] = "11";
     compressionMap["0101"] = "01";
     compressionMap["0110"] = "00";
-    compressionMap["0111"] = "11";
-    compressionMap["1000"] = "01";
+    compressionMap["0111"] = "01";
+    compressionMap["1000"] = "11";
     compressionMap["1001"] = "00";
     compressionMap["1010"] = "11";
     compressionMap["1011"] = "00";
diff --git a/GCryptLib/src/GCipher.cpp b/GCryptLib/src/GCipher.cpp
index 785d851..3a2883f 100644
--- a/GCryptLib/src/GCipher.cpp
+++ b/GCryptLib/src/GCipher.cpp
@@ -51,6 +51,12 @@ namespace Leonetienne::GCrypt {
     throw std::runtime_error("Unreachable branch reached.");
   }
 
+  void GCipher::SetKey(const Key& key) {
+    feistel.SetKey(key);
+
+    return;
+  }
+
   void GCipher::operator=(const GCipher& other) {
     direction = other.direction;
     feistel = other.feistel;
diff --git a/GCryptLib/src/GHash.cpp b/GCryptLib/src/GHash.cpp
index dec8f6c..5ea48fa 100644
--- a/GCryptLib/src/GHash.cpp
+++ b/GCryptLib/src/GHash.cpp
@@ -7,8 +7,8 @@ namespace Leonetienne::GCrypt {
   GHash::GHash() :
     // Initialize our cipher with a static, but randomly distributed key.
     cipher(
-        // Can't use Key::FromPassword here, because it depends on GHash.
-        // Instead use a hardcoded key.
+        // The key really does not matter, as it gets changed
+        // each time before digesting anything.
         Key(StringToBitblock("nsoCZfvdqpRkeVTt9wzvPR3TT26peOW9E2kTHh3pdPCq2M7BpskvUljJHSrobUTI")),
         GCipher::DIRECTION::ENCIPHER
     ) {
@@ -18,6 +18,9 @@ namespace Leonetienne::GCrypt {
   }
 
   void GHash::DigestBlock(const Block& data) {
+    // Set the cipher key to the current data to be hashed
+    cipher.SetKey(Key(data));
+
     // Encipher the current block, and xor it on the current hashsum
     block ^= cipher.Digest(data);
     return;