Enable extended output in SHAKE-128 and SHAKE-256 (GH #805, PR #806)

1 files changed, 33 insertions, 4 deletions

diff --git a/shake.h b/shake.h
index e9ce38a8..d044ebb1 100644
--- a/shake.h
+++ b/shake.h
@@ -47,6 +47,11 @@ public:
 protected:

     inline unsigned int r() const {return BlockSize();}

 

+    // SHAKE-128 and SHAKE-256 effectively allow unlimited

+    // output length. However, we use an unsigned int so

+    // we are limited in practice to UINT_MAX.

+    void ThrowIfInvalidTruncatedSize(size_t size) const;

+

     FixedSizeSecBlock<word64, 25> m_state;

     unsigned int m_digestSize, m_counter;

 };

@@ -64,7 +69,7 @@ public:
         { return "SHAKE-" + IntToString(T_Strength); }

 

     /// \brief Construct a SHAKE-X message digest

-    SHAKE_Final() : SHAKE(DIGESTSIZE) {}

+    SHAKE_Final(unsigned int outputSize=DIGESTSIZE) : SHAKE(outputSize) {}

 

     /// \brief Provides the block size of the compression function

     /// \return block size of the compression function, in bytes

@@ -79,17 +84,41 @@ private:
     // ensure there was no underflow in the math

     CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200);

     // this is a general expectation by HMAC

-    CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > (int)DIGESTSIZE);

+    CRYPTOPP_COMPILE_ASSERT((int)BLOCKSIZE > (int)DIGESTSIZE);

 #endif

 };

 

 /// \brief SHAKE128 message digest

 /// \since Crypto++ 8.1

-class SHAKE128 : public SHAKE_Final<128> {};

+class SHAKE128 : public SHAKE_Final<128>

+{

+public:

+    /// \details Construct a SHAKE128 message digest

+    /// \details SHAKE128() uses the default output digest size

+    /// \since Crypto++ 8.1

+    SHAKE128() {}

+

+    /// \details Construct a SHAKE128 message digest

+    /// \details SHAKE128() uses <tt>outputSize</tt> digest size

+    /// \since Crypto++ 8.1

+    SHAKE128(unsigned int outputSize) : SHAKE_Final(outputSize) {}

+};

 

 /// \brief SHAKE256 message digest

 /// \since Crypto++ 8.1

-class SHAKE256 : public SHAKE_Final<256> {};

+class SHAKE256 : public SHAKE_Final<256>

+{

+public:

+    /// \details Construct a SHAKE256 message digest

+    /// \details SHAKE256() uses the default output digest size

+    /// \since Crypto++ 8.1

+    SHAKE256() {}

+

+    /// \details Construct a SHAKE256 message digest

+    /// \details SHAKE256() uses <tt>outputSize</tt> digest size

+    /// \since Crypto++ 8.1

+    SHAKE256(unsigned int outputSize) : SHAKE_Final(outputSize) {}

+};

 

 NAMESPACE_END