1 files changed, 141 insertions, 0 deletions
diff --git a/src/stream/ctr/ctr.cpp b/src/stream/ctr/ctr.cpp
new file mode 100644
index 000000000..5f0880fa5
--- /dev/null
+++ b/src/stream/ctr/ctr.cpp
@@ -0,0 +1,141 @@
+/*
+* CTR-BE Mode Cipher
+* (C) 1999-2009 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/ctr.h>
+#include <botan/xor_buf.h>
+
+namespace Botan {
+
+/*
+* CTR-BE Constructor
+*/
+
+CTR_BE::CTR_BE(BlockCipher* ciph) :
+   StreamCipher(ciph->MINIMUM_KEYLENGTH,
+                ciph->MAXIMUM_KEYLENGTH,
+                ciph->KEYLENGTH_MULTIPLE),
+   permutation(ciph)
+   {
+   position = 0;
+
+   counter.create(permutation->BLOCK_SIZE * BOTAN_PARALLEL_BLOCKS_CTR);
+   buffer.create(permutation->BLOCK_SIZE * BOTAN_PARALLEL_BLOCKS_CTR);
+   }
+
+/*
+* CTR_BE Destructor
+*/
+CTR_BE::~CTR_BE()
+   {
+   delete permutation;
+   }
+
+/*
+* Zeroize
+*/
+void CTR_BE::clear()
+   {
+   permutation->clear();
+   buffer.clear();
+   counter.clear();
+   position = 0;
+   }
+
+/*
+* Set the key
+*/
+void CTR_BE::key_schedule(const byte key[], u32bit key_len)
+   {
+   permutation->set_key(key, key_len);
+
+   // Set a default all-zeros IV
+   set_iv(0, 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[], u32bit length)
+   {
+   while(length >= buffer.size() - position)
+      {
+      xor_buf(out, in, buffer.begin() + position, buffer.size() - position);
+      length -= (buffer.size() - position);
+      in += (buffer.size() - position);
+      out += (buffer.size() - position);
+      increment_counter();
+      }
+   xor_buf(out, in, buffer.begin() + position, length);
+   position += length;
+   }
+
+/*
+* Set CTR-BE IV
+*/
+void CTR_BE::set_iv(const byte iv[], u32bit iv_len)
+   {
+   if(!valid_iv_length(iv_len))
+      throw Invalid_IV_Length(name(), iv_len);
+
+   const u32bit BLOCK_SIZE = permutation->BLOCK_SIZE;
+
+   counter.clear();
+
+   counter.copy(0, iv, iv_len);
+
+   const u32bit PARALLEL_BLOCKS = counter.size() / BLOCK_SIZE;
+
+   for(u32bit i = 1; i != PARALLEL_BLOCKS; ++i)
+      {
+      counter.copy(i*BLOCK_SIZE,
+                   counter.begin() + (i-1)*BLOCK_SIZE, BLOCK_SIZE);
+
+      for(s32bit j = BLOCK_SIZE - 1; j >= 0; --j)
+         if(++counter[i*BLOCK_SIZE+j])
+            break;
+      }
+
+   permutation->encrypt_n(counter, buffer, PARALLEL_BLOCKS);
+   position = 0;
+   }
+
+/*
+* Increment the counter and update the buffer
+*/
+void CTR_BE::increment_counter()
+   {
+   const u32bit PARALLEL_BLOCKS = counter.size() / permutation->BLOCK_SIZE;
+
+   for(u32bit i = 0; i != PARALLEL_BLOCKS; ++i)
+      {
+      byte* this_ctr = counter + i*permutation->BLOCK_SIZE;
+
+      byte last_byte = this_ctr[permutation->BLOCK_SIZE-1];
+      last_byte += PARALLEL_BLOCKS;
+
+      if(this_ctr[permutation->BLOCK_SIZE-1] > last_byte)
+         for(s32bit j = permutation->BLOCK_SIZE - 2; j >= 0; --j)
+            if(++this_ctr[j])
+               break;
+
+      this_ctr[permutation->BLOCK_SIZE-1] = last_byte;
+      }
+
+   permutation->encrypt_n(counter, buffer, PARALLEL_BLOCKS);
+
+   position = 0;
+   }
+
+}