1 files changed, 74 insertions, 0 deletions
diff --git a/src/ctr.cpp b/src/ctr.cpp
new file mode 100644
index 000000000..f9c07eda8
--- /dev/null
+++ b/src/ctr.cpp
@@ -0,0 +1,74 @@
+/*************************************************
+* CTR Mode Source File                           *
+* (C) 1999-2006 The Botan Project                *
+*************************************************/
+
+#include <botan/ctr.h>
+#include <botan/lookup.h>
+#include <botan/bit_ops.h>
+#include <algorithm>
+
+namespace Botan {
+
+/*************************************************
+* CTR-BE Constructor                             *
+*************************************************/
+CTR_BE::CTR_BE(const std::string& cipher_name) :
+   BlockCipherMode(cipher_name, "CTR-BE", block_size_of(cipher_name), 1)
+   {
+   }
+
+/*************************************************
+* CTR-BE Constructor                             *
+*************************************************/
+CTR_BE::CTR_BE(const std::string& cipher_name, const SymmetricKey& key,
+               const InitializationVector& iv) :
+   BlockCipherMode(cipher_name, "CTR-BE", block_size_of(cipher_name), 1)
+   {
+   set_key(key);
+   set_iv(iv);
+   }
+
+/*************************************************
+* CTR-BE Encryption/Decryption                   *
+*************************************************/
+void CTR_BE::write(const byte input[], u32bit length)
+   {
+   u32bit copied = std::min(BLOCK_SIZE - position, length);
+   xor_buf(buffer + position, input, copied);
+   send(buffer + position, copied);
+   input += copied;
+   length -= copied;
+   position += copied;
+
+   if(position == BLOCK_SIZE)
+      increment_counter();
+
+   while(length >= BLOCK_SIZE)
+      {
+      xor_buf(buffer, input, BLOCK_SIZE);
+      send(buffer, BLOCK_SIZE);
+
+      input += BLOCK_SIZE;
+      length -= BLOCK_SIZE;
+      increment_counter();
+      }
+
+   xor_buf(buffer + position, input, length);
+   send(buffer + position, length);
+   position += length;
+   }
+
+/*************************************************
+* Increment the counter and update the buffer    *
+*************************************************/
+void CTR_BE::increment_counter()
+   {
+   for(s32bit j = BLOCK_SIZE - 1; j >= 0; --j)
+      if(++state[j])
+         break;
+   cipher->encrypt(state, buffer);
+   position = 0;
+   }
+
+}