Minor SIV/CMAC optimizations

2 files changed, 17 insertions, 13 deletions

diff --git a/src/lib/mac/cmac/cmac.cpp b/src/lib/mac/cmac/cmac.cpp
index 9e0a01853..18f7c151c 100644
--- a/src/lib/mac/cmac/cmac.cpp
+++ b/src/lib/mac/cmac/cmac.cpp
@@ -25,19 +25,21 @@ secure_vector<uint8_t> CMAC::poly_double(const secure_vector<uint8_t>& in)
 */
 void CMAC::add_data(const uint8_t input[], size_t length)
    {
+   const size_t bs = output_length();
+
    buffer_insert(m_buffer, m_position, input, length);
-   if(m_position + length > output_length())
+   if(m_position + length > bs)
       {
-      xor_buf(m_state, m_buffer, output_length());
+      xor_buf(m_state, m_buffer, bs);
       m_cipher->encrypt(m_state);
-      input += (output_length() - m_position);
-      length -= (output_length() - m_position);
-      while(length > output_length())
+      input += (bs - m_position);
+      length -= (bs - m_position);
+      while(length > bs)
          {
-         xor_buf(m_state, input, output_length());
+         xor_buf(m_state, input, bs);
          m_cipher->encrypt(m_state);
-         input += output_length();
-         length -= output_length();
+         input += bs;
+         length -= bs;
          }
       copy_mem(m_buffer.data(), input, length);
       m_position = 0;
@@ -64,8 +66,7 @@ void CMAC::final_result(uint8_t mac[])
 
    m_cipher->encrypt(m_state);
 
-   for(size_t i = 0; i != output_length(); ++i)
-      mac[i] = m_state[i];
+   copy_mem(mac, m_state.data(), output_length());
 
    zeroise(m_state);
    zeroise(m_buffer);
diff --git a/src/lib/modes/aead/siv/siv.cpp b/src/lib/modes/aead/siv/siv.cpp
index df9a0ef37..3a960e0af 100644
--- a/src/lib/modes/aead/siv/siv.cpp
+++ b/src/lib/modes/aead/siv/siv.cpp
@@ -16,7 +16,7 @@ namespace Botan {
 
 SIV_Mode::SIV_Mode(BlockCipher* cipher) :
    m_name(cipher->name() + "/SIV"),
-   m_ctr(new CTR_BE(cipher->clone())),
+   m_ctr(new CTR_BE(cipher->clone(), 8)),
    m_mac(new CMAC(cipher)),
    m_bs(cipher->block_size())
    {
@@ -173,8 +173,11 @@ void SIV_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
    {
    BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
 
-   buffer.insert(buffer.begin() + offset, msg_buf().begin(), msg_buf().end());
-   msg_buf().clear();
+   if(msg_buf().size() > 0)
+      {
+      buffer.insert(buffer.begin() + offset, msg_buf().begin(), msg_buf().end());
+      msg_buf().clear();
+      }
 
    const size_t sz = buffer.size() - offset;