Make XTS mode parallelizable (GH #891)

On CoffeeLake performance increased from 3.4 cpb to 1.75 cpb. On Core2Duo performance increased from 27 cpb to 19 cpb.

1 files changed, 9 insertions, 2 deletions

diff --git a/xts.h b/xts.h
index 6559dcc7..8b4234fe 100644
--- a/xts.h
+++ b/xts.h
@@ -49,6 +49,8 @@ NAMESPACE_BEGIN(CryptoPP)
 class CRYPTOPP_NO_VTABLE XTS_ModeBase : public BlockOrientedCipherModeBase

 {

 public:

+    virtual ~XTS_ModeBase() {}

+

     std::string AlgorithmName() const

         {return GetBlockCipher().AlgorithmName() + "/XTS";}

     std::string AlgorithmProvider() const

@@ -70,6 +72,8 @@ public:
     /// \return the block size of the cipher, in bytes

     unsigned int BlockSize() const

         {return GetBlockCipher().BlockSize();}

+    unsigned int GetOptimalBlockSize() const

+        {return GetBlockCipher().BlockSize()*ParallelBlocks;}

     unsigned int MinLastBlockSize() const

         {return GetBlockCipher().BlockSize()+1;}

     unsigned int OptimalDataAlignment() const

@@ -102,7 +106,10 @@ protected:
     const BlockCipher& GetTweakCipher() const

         {return const_cast<XTS_ModeBase*>(this)->AccessTweakCipher();}

 

-    SecByteBlock m_workspace;

+    SecByteBlock m_xregister;

+    SecByteBlock m_xworkspace;

+

+    enum {ParallelBlocks = 4};

 };

 

 /// \brief XTS block cipher mode of operation implementation details

@@ -112,7 +119,7 @@ template <class CIPHER>
 class CRYPTOPP_NO_VTABLE XTS_Final : public XTS_ModeBase

 {

 public:

-    static const char* CRYPTOPP_API StaticAlgorithmName()

+    CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName()

         {return "XTS";}

 

 protected: