diff --git a/cbcmac.cpp b/cbcmac.cpp
index e262535d..dfac071b 100644
--- a/cbcmac.cpp
+++ b/cbcmac.cpp
@@ -6,7 +6,7 @@
 
 NAMESPACE_BEGIN(CryptoPP)
 
-void CBC_MAC_Base::UncheckedSetKey(const byte *key, size_t length, const NameValuePairs &params)
+void CBC_MAC_Base::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
 {
 	AccessCipher().SetKey(key, length, params);
 	m_reg.CleanNew(AccessCipher().BlockSize());
diff --git a/cbcmac.h b/cbcmac.h
index 30566d0f..a8c88d36 100644
--- a/cbcmac.h
+++ b/cbcmac.h
@@ -12,7 +12,7 @@ class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE CBC_MAC_Base : public MessageAuthenticatio
 public:
 	CBC_MAC_Base() {}
 
-	void UncheckedSetKey(const byte *key, size_t length, const NameValuePairs &params);
+	void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);
 	void Update(const byte *input, size_t length);
 	void TruncatedFinal(byte *mac, size_t size);
 	unsigned int DigestSize() const {return const_cast<CBC_MAC_Base*>(this)->AccessCipher().BlockSize();}
diff --git a/dmac.h b/dmac.h
index d7522f74..c0f81b3d 100644
--- a/dmac.h
+++ b/dmac.h
@@ -16,7 +16,7 @@ public:
 
 	DMAC_Base() {}
 
-	void UncheckedSetKey(const byte *key, size_t length, const NameValuePairs &params);
+	void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);
 	void Update(const byte *input, size_t length);
 	void TruncatedFinal(byte *mac, size_t size);
 	unsigned int DigestSize() const {return DIGESTSIZE;}
@@ -45,7 +45,7 @@ public:
 };
 
 template <class T>
-void DMAC_Base<T>::UncheckedSetKey(const byte *key, size_t length, const NameValuePairs &params)
+void DMAC_Base<T>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
 {
 	m_subkeylength = T::StaticGetValidKeyLength(T::BLOCKSIZE);
 	m_subkeys.resize(2*UnsignedMin((unsigned int)T::BLOCKSIZE, m_subkeylength));
diff --git a/panama.h b/panama.h
index ce34c73d..ffad8aea 100644
--- a/panama.h
+++ b/panama.h
@@ -46,7 +46,7 @@ template <class T_Hash, class T_Info = T_Hash>
 class HermeticHashFunctionMAC : public AlgorithmImpl<SimpleKeyingInterfaceImpl<TwoBases<MessageAuthenticationCode, VariableKeyLength<32, 0, UINT_MAX> > >, T_Info>
 {
 public:
-	void UncheckedSetKey(const byte *key, size_t length, const NameValuePairs &params)
+	void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
 	{
 		m_key.Assign(key, length);
 		Restart();
diff --git a/xormac.h b/xormac.h
index 7c121d8c..3afb816d 100644
--- a/xormac.h
+++ b/xormac.h
@@ -23,7 +23,7 @@ public:
 
 	XMACC_Base() {SetStateSize(T::DIGESTSIZE);}
 
-	void UncheckedSetKey(const byte *key, size_t length, const NameValuePairs &params);
+	void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);
 	void Resynchronize(const byte *IV)
 	{
 		GetWord(false, BIG_ENDIAN_ORDER, m_counter, IV);
@@ -70,7 +70,7 @@ public:
 		{this->SetKey(key, this->KEYLENGTH, MakeParameters(Name::XMACC_Counter(), counter));}
 };
 
-template <class T> void XMACC_Base<T>::UncheckedSetKey(const byte *key, size_t length, const NameValuePairs &params)
+template <class T> void XMACC_Base<T>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
 {
 	this->AssertValidKeyLength(length);
 	m_counter = 0xffffffff;