diff --git a/strciphr.cpp b/strciphr.cpp
index 6aae6318..82dd55ea 100644
--- a/strciphr.cpp
+++ b/strciphr.cpp
@@ -39,15 +39,27 @@ void AdditiveCipherTemplate<S>::GenerateBlock(byte *outString, size_t length)
 		if (!length)
 			return;
 	}
-	CRYPTOPP_ASSERT(m_leftOver == 0);
 
 	PolicyInterface &policy = this->AccessPolicy();
-	unsigned int bytesPerIteration = policy.GetBytesPerIteration();
+	const unsigned int bytesPerIteration = policy.GetBytesPerIteration();
+	const unsigned int alignment = policy.GetAlignment();
 
 	if (length >= bytesPerIteration)
 	{
-		size_t iterations = length / bytesPerIteration;
-		policy.WriteKeystream(outString, iterations);
+		const size_t iterations = length / bytesPerIteration;
+
+		// Intel and ARM SIMD units can handle unaligned loads of
+		//   byte buffers, but AltiVec and Power8 cannot.
+		if (!IsAlignedOn(outString, alignment))
+		{
+			AlignedSecByteBlock temp(iterations * bytesPerIteration);
+			policy.WriteKeystream(temp, iterations);
+			memcpy(outString, temp, iterations * bytesPerIteration);
+		}
+		else
+		{
+			policy.WriteKeystream(outString, iterations);
+		}
 		outString += iterations * bytesPerIteration;
 		length -= iterations * bytesPerIteration;
 	}
@@ -78,15 +90,14 @@ void AdditiveCipherTemplate<S>::ProcessData(byte *outString, const byte *inStrin
 		if (!length)
 			return;
 	}
-	CRYPTOPP_ASSERT(m_leftOver == 0);
 
 	PolicyInterface &policy = this->AccessPolicy();
-	unsigned int bytesPerIteration = policy.GetBytesPerIteration();
+	const unsigned int bytesPerIteration = policy.GetBytesPerIteration();
+	const unsigned int alignment = policy.GetAlignment();
 
 	if (policy.CanOperateKeystream() && length >= bytesPerIteration)
 	{
-		size_t iterations = length / bytesPerIteration;
-		unsigned int alignment = policy.GetAlignment();
+		const size_t iterations = length / bytesPerIteration;
 		KeystreamOperation operation = KeystreamOperation((IsAlignedOn(inString, alignment) * 2) | (int)IsAlignedOn(outString, alignment));
 
 		policy.OperateKeystream(operation, outString, inString, iterations);
@@ -179,8 +190,8 @@ void CFB_CipherTemplate<BASE>::ProcessData(byte *outString, const byte *inString
 	CRYPTOPP_ASSERT(length % this->MandatoryBlockSize() == 0);
 
 	PolicyInterface &policy = this->AccessPolicy();
-	unsigned int bytesPerIteration = policy.GetBytesPerIteration();
-	unsigned int alignment = policy.GetAlignment();
+	const unsigned int bytesPerIteration = policy.GetBytesPerIteration();
+	const unsigned int alignment = policy.GetAlignment();
 	byte *reg = policy.GetRegisterBegin();
 
 	if (m_leftOver)
@@ -196,8 +207,6 @@ void CFB_CipherTemplate<BASE>::ProcessData(byte *outString, const byte *inString
 	if (!length)
 		return;
 
-	CRYPTOPP_ASSERT(m_leftOver == 0);
-
 	if (policy.CanIterate() && length >= bytesPerIteration && IsAlignedOn(outString, alignment))
 	{
 		if (IsAlignedOn(inString, alignment))
diff --git a/strciphr.h b/strciphr.h
index 10082907..bc105a27 100644
--- a/strciphr.h
+++ b/strciphr.h
@@ -187,13 +187,12 @@ struct CRYPTOPP_NO_VTABLE AdditiveCipherConcretePolicy : public BASE
 	typedef WT WordType;
 	CRYPTOPP_CONSTANT(BYTES_PER_ITERATION = sizeof(WordType) * W)
 
-#if !(CRYPTOPP_BOOL_X86 || CRYPTOPP_BOOL_X64)
 	//! \brief Provides data alignment requirements
 	//! \returns data alignment requirements, in bytes
 	//! \details Internally, the default implementation returns 1. If the stream cipher is implemented
-	//!   using an SSE2 ASM or intrinsics, then the value returned is usually 16.
+	//!   using an SSE2 ASM or intrinsics, then the value returned is usually 16. If the cipher is
+	//!   AES on AltiVec or Power 8 then 16 is returned.
 	unsigned int GetAlignment() const {return GetAlignmentOf<WordType>();}
-#endif
 
 	//! \brief Provides number of bytes operated upon during an iteration
 	//! \returns bytes operated upon during an iteration, in bytes
@@ -340,7 +339,7 @@ protected:
 	inline byte * KeystreamBufferBegin() {return this->m_buffer.data();}
 	inline byte * KeystreamBufferEnd() {return (this->m_buffer.data() + this->m_buffer.size());}
 
-	SecByteBlock m_buffer;
+	AlignedSecByteBlock m_buffer;
 	size_t m_leftOver;
 };