1 files changed, 134 insertions, 0 deletions
diff --git a/src/lib/stream/ctr/ctr.cpp b/src/lib/stream/ctr/ctr.cpp
new file mode 100644
index 000000000..87ec86c65
--- /dev/null
+++ b/src/lib/stream/ctr/ctr.cpp
@@ -0,0 +1,134 @@
+/*
+* Counter mode
+* (C) 1999-2011 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/ctr.h>
+#include <botan/internal/xor_buf.h>
+
+namespace Botan {
+
+/*
+* CTR-BE Constructor
+*/
+
+CTR_BE::CTR_BE(BlockCipher* ciph) :
+   permutation(ciph),
+   counter(256 * permutation->block_size()),
+   buffer(counter.size()),
+   position(0)
+   {
+   }
+
+/*
+* CTR_BE Destructor
+*/
+CTR_BE::~CTR_BE()
+   {
+   delete permutation;
+   }
+
+/*
+* Zeroize
+*/
+void CTR_BE::clear()
+   {
+   permutation->clear();
+   zeroise(buffer);
+   zeroise(counter);
+   position = 0;
+   }
+
+/*
+* Set the key
+*/
+void CTR_BE::key_schedule(const byte key[], size_t key_len)
+   {
+   permutation->set_key(key, key_len);
+
+   // Set a default all-zeros IV
+   set_iv(nullptr, 0);
+   }
+
+/*
+* Return the name of this type
+*/
+std::string CTR_BE::name() const
+   {
+   return ("CTR-BE(" + permutation->name() + ")");
+   }
+
+/*
+* CTR-BE Encryption/Decryption
+*/
+void CTR_BE::cipher(const byte in[], byte out[], size_t length)
+   {
+   while(length >= buffer.size() - position)
+      {
+      xor_buf(out, in, &buffer[position], buffer.size() - position);
+      length -= (buffer.size() - position);
+      in += (buffer.size() - position);
+      out += (buffer.size() - position);
+      increment_counter();
+      }
+   xor_buf(out, in, &buffer[position], length);
+   position += length;
+   }
+
+/*
+* Set CTR-BE IV
+*/
+void CTR_BE::set_iv(const byte iv[], size_t iv_len)
+   {
+   if(!valid_iv_length(iv_len))
+      throw Invalid_IV_Length(name(), iv_len);
+
+   const size_t bs = permutation->block_size();
+
+   zeroise(counter);
+
+   buffer_insert(counter, 0, iv, iv_len);
+
+   /*
+   * Set counter blocks to IV, IV + 1, ... IV + 255
+   */
+   for(size_t i = 1; i != 256; ++i)
+      {
+      buffer_insert(counter, i*bs, &counter[(i-1)*bs], bs);
+
+      for(size_t j = 0; j != bs; ++j)
+         if(++counter[i*bs + (bs - 1 - j)])
+            break;
+      }
+
+   permutation->encrypt_n(&counter[0], &buffer[0], 256);
+   position = 0;
+   }
+
+/*
+* Increment the counter and update the buffer
+*/
+void CTR_BE::increment_counter()
+   {
+   const size_t bs = permutation->block_size();
+
+   /*
+   * Each counter value always needs to be incremented by 256,
+   * so we don't touch the lowest byte and instead treat it as
+   * an increment of one starting with the next byte.
+   */
+   for(size_t i = 0; i != 256; ++i)
+      {
+      for(size_t j = 1; j != bs; ++j)
+         if(++counter[i*bs + (bs - 1 - j)])
+            break;
+      }
+
+   permutation->encrypt_n(&counter[0], &buffer[0], 256);
+
+   position = 0;
+   }
+
+}