1 files changed, 102 insertions, 0 deletions
diff --git a/lib/hash/comb4p/comb4p.cpp b/lib/hash/comb4p/comb4p.cpp
new file mode 100644
index 000000000..7aec5972e
--- /dev/null
+++ b/lib/hash/comb4p/comb4p.cpp
@@ -0,0 +1,102 @@
+/*
+* Comb4P hash combiner
+* (C) 2010 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/comb4p.h>
+#include <botan/internal/xor_buf.h>
+#include <stdexcept>
+
+namespace Botan {
+
+namespace {
+
+void comb4p_round(secure_vector<byte>& out,
+                  const secure_vector<byte>& in,
+                  byte round_no,
+                  HashFunction* h1,
+                  HashFunction* h2)
+   {
+   h1->update(round_no);
+   h2->update(round_no);
+
+   h1->update(&in[0], in.size());
+   h2->update(&in[0], in.size());
+
+   secure_vector<byte> h_buf = h1->final();
+   xor_buf(&out[0], &h_buf[0], std::min(out.size(), h_buf.size()));
+
+   h_buf = h2->final();
+   xor_buf(&out[0], &h_buf[0], std::min(out.size(), h_buf.size()));
+   }
+
+}
+
+Comb4P::Comb4P(HashFunction* h1, HashFunction* h2) :
+   hash1(h1), hash2(h2)
+   {
+   if(hash1->name() == hash2->name())
+      throw std::invalid_argument("Comb4P: Must use two distinct hashes");
+
+   if(hash1->output_length() != hash2->output_length())
+      throw std::invalid_argument("Comb4P: Incompatible hashes " +
+                                  hash1->name() + " and " +
+                                  hash2->name());
+
+   clear();
+   }
+
+size_t Comb4P::hash_block_size() const
+   {
+   if(hash1->hash_block_size() == hash2->hash_block_size())
+      return hash1->hash_block_size();
+
+   /*
+   * Return LCM of the block sizes? This would probably be OK for
+   * HMAC, which is the main thing relying on knowing the block size.
+   */
+   return 0;
+   }
+
+void Comb4P::clear()
+   {
+   hash1->clear();
+   hash2->clear();
+
+   // Prep for processing next message, if any
+   hash1->update(0);
+   hash2->update(0);
+   }
+
+void Comb4P::add_data(const byte input[], size_t length)
+   {
+   hash1->update(input, length);
+   hash2->update(input, length);
+   }
+
+void Comb4P::final_result(byte out[])
+   {
+   secure_vector<byte> h1 = hash1->final();
+   secure_vector<byte> h2 = hash2->final();
+
+   // First round
+   xor_buf(&h1[0], &h2[0], std::min(h1.size(), h2.size()));
+
+   // Second round
+   comb4p_round(h2, h1, 1, hash1, hash2);
+
+   // Third round
+   comb4p_round(h1, h2, 2, hash1, hash2);
+
+   copy_mem(out            , &h1[0], h1.size());
+   copy_mem(out + h1.size(), &h2[0], h2.size());
+
+   // Prep for processing next message, if any
+   hash1->update(0);
+   hash2->update(0);
+   }
+
+}
+