diff --git a/keccak.h b/keccak.h
index d3580ec1..0349b464 100644
--- a/keccak.h
+++ b/keccak.h
@@ -56,6 +56,8 @@ public:
 	void Restart();
 	void TruncatedFinal(byte *hash, size_t size);
 
+	//unsigned int BlockSize() const { return r(); } // that's the idea behind it
+
 protected:
 	inline unsigned int r() const {return 200 - 2 * m_digestSize;}
 
@@ -70,10 +72,15 @@ class Keccak_224 : public Keccak
 {
 public:
 	CRYPTOPP_CONSTANT(DIGESTSIZE = 28)
+	CRYPTOPP_CONSTANT(BLOCKSIZE = 200 - 2 * DIGESTSIZE)
 
 	//! \brief Construct a Keccak-224 message digest
 	Keccak_224() : Keccak(DIGESTSIZE) {}
 	CRYPTOPP_CONSTEXPR static const char *StaticAlgorithmName() {return "Keccak-224";}
+	unsigned int BlockSize() const { return BLOCKSIZE; }
+private:
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200); // ensure there was no underflow in the math
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > DIGESTSIZE); // this is a general expectation by HMAC
 };
 
 //! \class Keccak_256
@@ -83,10 +90,15 @@ class Keccak_256 : public Keccak
 {
 public:
 	CRYPTOPP_CONSTANT(DIGESTSIZE = 32)
+	CRYPTOPP_CONSTANT(BLOCKSIZE = 200 - 2 * DIGESTSIZE)
 
 	//! \brief Construct a Keccak-256 message digest
 	Keccak_256() : Keccak(DIGESTSIZE) {}
 	CRYPTOPP_CONSTEXPR static const char *StaticAlgorithmName() {return "Keccak-256";}
+	unsigned int BlockSize() const { return BLOCKSIZE; }
+private:
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200); // ensure there was no underflow in the math
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > DIGESTSIZE); // this is a general expectation by HMAC
 };
 
 //! \class Keccak_384
@@ -96,10 +108,15 @@ class Keccak_384 : public Keccak
 {
 public:
 	CRYPTOPP_CONSTANT(DIGESTSIZE = 48)
+	CRYPTOPP_CONSTANT(BLOCKSIZE = 200 - 2 * DIGESTSIZE)
 
 	//! \brief Construct a Keccak-384 message digest
 	Keccak_384() : Keccak(DIGESTSIZE) {}
 	CRYPTOPP_CONSTEXPR static const char *StaticAlgorithmName() {return "Keccak-384";}
+	unsigned int BlockSize() const { return BLOCKSIZE; }
+private:
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200); // ensure there was no underflow in the math
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > DIGESTSIZE); // this is a general expectation by HMAC
 };
 
 //! \class Keccak_512
@@ -109,10 +126,15 @@ class Keccak_512 : public Keccak
 {
 public:
 	CRYPTOPP_CONSTANT(DIGESTSIZE = 64)
+	CRYPTOPP_CONSTANT(BLOCKSIZE = 200 - 2 * DIGESTSIZE)
 
 	//! \brief Construct a Keccak-512 message digest
 	Keccak_512() : Keccak(DIGESTSIZE) {}
 	CRYPTOPP_CONSTEXPR static const char *StaticAlgorithmName() {return "Keccak-512";}
+	unsigned int BlockSize() const { return BLOCKSIZE; }
+private:
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200); // ensure there was no underflow in the math
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > DIGESTSIZE); // this is a general expectation by HMAC
 };
 
 NAMESPACE_END
diff --git a/sha3.h b/sha3.h
index 6a8704c8..f2d3b742 100644
--- a/sha3.h
+++ b/sha3.h
@@ -42,6 +42,7 @@ public:
 	void Restart();
 	void TruncatedFinal(byte *hash, size_t size);
 
+	// unsigned int BlockSize() const { return r(); } // that's the idea behind it
 protected:
 	inline unsigned int r() const {return 200 - 2 * m_digestSize;}
 
@@ -56,10 +57,15 @@ class SHA3_224 : public SHA3
 {
 public:
 	CRYPTOPP_CONSTANT(DIGESTSIZE = 28)
+	CRYPTOPP_CONSTANT(BLOCKSIZE = 200 - 2 * DIGESTSIZE)
 
 	//! \brief Construct a SHA3-224 message digest
 	SHA3_224() : SHA3(DIGESTSIZE) {}
 	CRYPTOPP_CONSTEXPR static const char *StaticAlgorithmName() {return "SHA3-224";}
+	unsigned int BlockSize() const { return BLOCKSIZE; }
+private:
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200); // ensure there was no underflow in the math
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > DIGESTSIZE); // this is a general expectation by HMAC
 };
 
 //! \class SHA3_256
@@ -69,10 +75,15 @@ class SHA3_256 : public SHA3
 {
 public:
 	CRYPTOPP_CONSTANT(DIGESTSIZE = 32)
+	CRYPTOPP_CONSTANT(BLOCKSIZE = 200 - 2 * DIGESTSIZE)
 
 	//! \brief Construct a SHA3-256 message digest
 	SHA3_256() : SHA3(DIGESTSIZE) {}
 	CRYPTOPP_CONSTEXPR static const char *StaticAlgorithmName() {return "SHA3-256";}
+	unsigned int BlockSize() const { return BLOCKSIZE; }
+private:
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200); // ensure there was no underflow in the math
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > DIGESTSIZE); // this is a general expectation by HMAC
 };
 
 //! \class SHA3_384
@@ -82,10 +93,15 @@ class SHA3_384 : public SHA3
 {
 public:
 	CRYPTOPP_CONSTANT(DIGESTSIZE = 48)
+	CRYPTOPP_CONSTANT(BLOCKSIZE = 200 - 2 * DIGESTSIZE)
 
 	//! \brief Construct a SHA3-384 message digest
 	SHA3_384() : SHA3(DIGESTSIZE) {}
 	CRYPTOPP_CONSTEXPR static const char *StaticAlgorithmName() {return "SHA3-384";}
+	unsigned int BlockSize() const { return BLOCKSIZE; }
+private:
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200); // ensure there was no underflow in the math
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > DIGESTSIZE); // this is a general expectation by HMAC
 };
 
 //! \class SHA3_512
@@ -95,10 +111,15 @@ class SHA3_512 : public SHA3
 {
 public:
 	CRYPTOPP_CONSTANT(DIGESTSIZE = 64)
+	CRYPTOPP_CONSTANT(BLOCKSIZE = 200 - 2 * DIGESTSIZE)
 
 	//! \brief Construct a SHA3-512 message digest
 	SHA3_512() : SHA3(DIGESTSIZE) {}
 	CRYPTOPP_CONSTEXPR static const char *StaticAlgorithmName() {return "SHA3-512";}
+	unsigned int BlockSize() const { return BLOCKSIZE; }
+private:
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE < 200); // ensure there was no underflow in the math
+	CRYPTOPP_COMPILE_ASSERT(BLOCKSIZE > DIGESTSIZE); // this is a general expectation by HMAC
 };
 
 NAMESPACE_END