diff --git a/chacha-simd.cpp b/chacha-simd.cpp
index e4d24178..6ec01834 100644
--- a/chacha-simd.cpp
+++ b/chacha-simd.cpp
@@ -193,7 +193,7 @@ NAMESPACE_BEGIN(CryptoPP)
 
 #if (CRYPTOPP_ARM_NEON_AVAILABLE)
 
-void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *output, unsigned int rounds, bool xorInput)
+void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *output, unsigned int rounds)
 {
     const uint32x4_t state0 = vld1q_u32(state + 0*4);
     const uint32x4_t state1 = vld1q_u32(state + 1*4);
@@ -408,7 +408,7 @@ void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *
     r3_3 = vreinterpretq_u32_u64(vaddq_u64(
              vreinterpretq_u64_u32(r3_3), CTRS[2]));
 
-    if (xorInput)
+    if (input)
     {
         r0_0 = veorq_u32(vreinterpretq_u32_u8(vld1q_u8(input + 0*16)), r0_0);
         r0_1 = veorq_u32(vreinterpretq_u32_u8(vld1q_u8(input + 1*16)), r0_1);
@@ -421,7 +421,7 @@ void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *
     vst1q_u8(output + 2*16, vreinterpretq_u8_u32(r0_2));
     vst1q_u8(output + 3*16, vreinterpretq_u8_u32(r0_3));
 
-    if (xorInput)
+    if (input)
     {
         r1_0 = veorq_u32(vreinterpretq_u32_u8(vld1q_u8(input + 4*16)), r1_0);
         r1_1 = veorq_u32(vreinterpretq_u32_u8(vld1q_u8(input + 5*16)), r1_1);
@@ -434,7 +434,7 @@ void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *
     vst1q_u8(output + 6*16, vreinterpretq_u8_u32(r1_2));
     vst1q_u8(output + 7*16, vreinterpretq_u8_u32(r1_3));
 
-    if (xorInput)
+    if (input)
     {
         r2_0 = veorq_u32(vreinterpretq_u32_u8(vld1q_u8(input +  8*16)), r2_0);
         r2_1 = veorq_u32(vreinterpretq_u32_u8(vld1q_u8(input +  9*16)), r2_1);
@@ -447,7 +447,7 @@ void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *
     vst1q_u8(output + 10*16, vreinterpretq_u8_u32(r2_2));
     vst1q_u8(output + 11*16, vreinterpretq_u8_u32(r2_3));
 
-    if (xorInput)
+    if (input)
     {
         r3_0 = veorq_u32(vreinterpretq_u32_u8(vld1q_u8(input + 12*16)), r3_0);
         r3_1 = veorq_u32(vreinterpretq_u32_u8(vld1q_u8(input + 13*16)), r3_1);
@@ -467,7 +467,7 @@ void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *
 
 #if (CRYPTOPP_SSE2_INTRIN_AVAILABLE || CRYPTOPP_SSE2_ASM_AVAILABLE)
 
-void ChaCha_OperateKeystream_SSE2(const word32 *state, const byte* input, byte *output, unsigned int rounds, bool xorInput)
+void ChaCha_OperateKeystream_SSE2(const word32 *state, const byte* input, byte *output, unsigned int rounds)
 {
     const __m128i* state_mm = reinterpret_cast<const __m128i*>(state);
     const __m128i* input_mm = reinterpret_cast<const __m128i*>(input);
@@ -676,7 +676,7 @@ void ChaCha_OperateKeystream_SSE2(const word32 *state, const byte* input, byte *
     r3_3 = _mm_add_epi32(r3_3, state3);
     r3_3 = _mm_add_epi64(r3_3, _mm_set_epi32(0, 0, 0, 3));
 
-    if (xorInput)
+    if (input_mm)
     {
         r0_0 = _mm_xor_si128(_mm_loadu_si128(input_mm + 0), r0_0);
         r0_1 = _mm_xor_si128(_mm_loadu_si128(input_mm + 1), r0_1);
@@ -689,7 +689,7 @@ void ChaCha_OperateKeystream_SSE2(const word32 *state, const byte* input, byte *
     _mm_storeu_si128(output_mm + 2, r0_2);
     _mm_storeu_si128(output_mm + 3, r0_3);
 
-    if (xorInput)
+    if (input_mm)
     {
         r1_0 = _mm_xor_si128(_mm_loadu_si128(input_mm + 4), r1_0);
         r1_1 = _mm_xor_si128(_mm_loadu_si128(input_mm + 5), r1_1);
@@ -702,7 +702,7 @@ void ChaCha_OperateKeystream_SSE2(const word32 *state, const byte* input, byte *
     _mm_storeu_si128(output_mm + 6, r1_2);
     _mm_storeu_si128(output_mm + 7, r1_3);
 
-    if (xorInput)
+    if (input_mm)
     {
         r2_0 = _mm_xor_si128(_mm_loadu_si128(input_mm + 8), r2_0);
         r2_1 = _mm_xor_si128(_mm_loadu_si128(input_mm + 9), r2_1);
@@ -715,7 +715,7 @@ void ChaCha_OperateKeystream_SSE2(const word32 *state, const byte* input, byte *
     _mm_storeu_si128(output_mm + 10, r2_2);
     _mm_storeu_si128(output_mm + 11, r2_3);
 
-    if (xorInput)
+    if (input_mm)
     {
         r3_0 = _mm_xor_si128(_mm_loadu_si128(input_mm + 12), r3_0);
         r3_1 = _mm_xor_si128(_mm_loadu_si128(input_mm + 13), r3_1);
diff --git a/chacha.cpp b/chacha.cpp
index 723f37f2..63b24845 100644
--- a/chacha.cpp
+++ b/chacha.cpp
@@ -12,11 +12,11 @@
 NAMESPACE_BEGIN(CryptoPP)
 
 #if (CRYPTOPP_ARM_NEON_AVAILABLE)
-extern void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *output, unsigned int rounds, bool xorInput);
+extern void ChaCha_OperateKeystream_NEON(const word32 *state, const byte* input, byte *output, unsigned int rounds);
 #endif
 
 #if (CRYPTOPP_SSE2_INTRIN_AVAILABLE || CRYPTOPP_SSE2_ASM_AVAILABLE)
-extern void ChaCha_OperateKeystream_SSE2(const word32 *state, const byte* input, byte *output, unsigned int rounds, bool xorInput);
+extern void ChaCha_OperateKeystream_SSE2(const word32 *state, const byte* input, byte *output, unsigned int rounds);
 #endif
 
 #define CHACHA_QUARTER_ROUND(a,b,c,d) \
@@ -124,8 +124,8 @@ void ChaCha_Policy::OperateKeystream(KeystreamOperation operation,
     {
         while (iterationCount >= 4)
         {
-            bool xorInput = (operation & INPUT_NULL) != INPUT_NULL;
-            ChaCha_OperateKeystream_SSE2(m_state, input, output, m_rounds, xorInput);
+            const bool xorInput = (operation & INPUT_NULL) != INPUT_NULL;
+            ChaCha_OperateKeystream_SSE2(m_state, xorInput ? input : NULLPTR, output, m_rounds);
 
             m_state[12] += 4;
             if (m_state[12] < 4)
@@ -143,8 +143,8 @@ void ChaCha_Policy::OperateKeystream(KeystreamOperation operation,
     {
         while (iterationCount >= 4)
         {
-            bool xorInput = (operation & INPUT_NULL) != INPUT_NULL;
-            ChaCha_OperateKeystream_NEON(m_state, input, output, m_rounds, xorInput);
+            const bool xorInput = (operation & INPUT_NULL) != INPUT_NULL;
+            ChaCha_OperateKeystream_NEON(m_state, xorInput ? input : NULLPTR, output, m_rounds);
 
             m_state[12] += 4;
             if (m_state[12] < 4)
@@ -163,8 +163,8 @@ void ChaCha_Policy::OperateKeystream(KeystreamOperation operation,
 
         x0 = m_state[0];    x1 = m_state[1];    x2 = m_state[2];    x3 = m_state[3];
         x4 = m_state[4];    x5 = m_state[5];    x6 = m_state[6];    x7 = m_state[7];
-        x8 = m_state[8];    x9 = m_state[9];    x10 = m_state[10];    x11 = m_state[11];
-        x12 = m_state[12];    x13 = m_state[13];    x14 = m_state[14];    x15 = m_state[15];
+        x8 = m_state[8];    x9 = m_state[9];    x10 = m_state[10];  x11 = m_state[11];
+        x12 = m_state[12];  x13 = m_state[13];  x14 = m_state[14];  x15 = m_state[15];
 
         for (int i = static_cast<int>(m_rounds); i > 0; i -= 2)
         {