propagate from branch 'net.randombit.botan' (head 039c91aa543bad85f227e8127ed048f9005e2fa0)

            to branch 'net.randombit.botan.aead-modes' (head 97d8d24b545f18084e39bf928c174c45efbb63bd)

12 files changed, 845 insertions, 3 deletions

diff --git a/checks/bench.cpp b/checks/bench.cpp
index 5faba00db..f7ddc5650 100644
--- a/checks/bench.cpp
+++ b/checks/bench.cpp
@@ -76,6 +76,7 @@ const std::string algos[] = {
    "AES-128/CBC/CTS",
    "AES-128/CTR-BE",
    "AES-128/EAX",
+   "AES-128/OCB",
    "AES-128/OFB",
    "AES-128/XTS",
    "AES-128/CFB(128)",
@@ -202,10 +203,13 @@ bool bench_algo(const std::string& algo,
          }
 
       size_t cipher_keylen = proto_cipher->maximum_keylength();
-      const size_t cipher_ivlen = proto_cipher->block_size();
+      size_t cipher_ivlen = proto_cipher->block_size();
 
+      // hacks!
       if(algo_parts[1] == "XTS")
-         cipher_keylen *= 2; // hack!
+         cipher_keylen *= 2;
+      if(algo_parts[1] == "OCB")
+         cipher_ivlen -= 1;
 
       std::vector<byte> buf(16 * 1024);
       rng.randomize(&buf[0], buf.size());
diff --git a/checks/ocb.cpp b/checks/ocb.cpp
new file mode 100644
index 000000000..78be74bef
--- /dev/null
+++ b/checks/ocb.cpp
@@ -0,0 +1,250 @@
+
+#include "validate.h"
+
+#include <botan/pipe.h>
+#include <botan/ocb.h>
+#include <botan/hex.h>
+#include <botan/sha2_32.h>
+#include <botan/aes.h>
+#include <iostream>
+//#include <botan/selftest.h>
+
+using namespace Botan;
+
+// something like this should be in the library
+std::vector<byte> ocb_encrypt(const SymmetricKey& key,
+                              const std::vector<byte>& nonce,
+                              const byte pt[], size_t pt_len,
+                              const byte ad[], size_t ad_len)
+   {
+   //std::unique_ptr<AEAD_Mode> ocb = get_aead("AES-128/OCB", ENCRYPTION);
+
+   OCB_Encryption* ocb = new OCB_Encryption(new AES_128);
+
+   ocb->set_key(key);
+   ocb->set_nonce(&nonce[0], nonce.size());
+   ocb->set_associated_data(ad, ad_len);
+
+   Pipe pipe(ocb);
+   pipe.process_msg(pt, pt_len);
+   return unlock(pipe.read_all());
+   }
+
+std::vector<byte> ocb_decrypt(const SymmetricKey& key,
+                              const std::vector<byte>& nonce,
+                              const byte pt[], size_t pt_len,
+                              const byte ad[], size_t ad_len)
+   {
+   OCB_Decryption* ocb = new OCB_Decryption(new AES_128);
+
+   ocb->set_key(key);
+   ocb->set_nonce(&nonce[0], nonce.size());
+   ocb->set_associated_data(ad, ad_len);
+
+   Pipe pipe(ocb);
+   pipe.process_msg(pt, pt_len);
+   return unlock(pipe.read_all());
+   }
+
+template<typename Alloc, typename Alloc2>
+std::vector<byte> ocb_encrypt(const SymmetricKey& key,
+                              const std::vector<byte>& nonce,
+                              const std::vector<byte, Alloc>& pt,
+                              const std::vector<byte, Alloc2>& ad)
+   {
+   return ocb_encrypt(key, nonce, &pt[0], pt.size(), &ad[0], ad.size());
+   }
+
+template<typename Alloc, typename Alloc2>
+std::vector<byte> ocb_decrypt(const SymmetricKey& key,
+                              const std::vector<byte>& nonce,
+                              const std::vector<byte, Alloc>& pt,
+                              const std::vector<byte, Alloc2>& ad)
+   {
+   return ocb_decrypt(key, nonce, &pt[0], pt.size(), &ad[0], ad.size());
+   }
+
+std::vector<byte> ocb_encrypt(OCB_Encryption& ocb,
+                              Pipe& pipe,
+                              const std::vector<byte>& nonce,
+                              const std::vector<byte>& pt,
+                              const std::vector<byte>& ad)
+   {
+   ocb.set_nonce(&nonce[0], nonce.size());
+   ocb.set_associated_data(&ad[0], ad.size());
+
+   pipe.process_msg(pt);
+   return unlock(pipe.read_all(Pipe::LAST_MESSAGE));
+   }
+
+void test_ocb_long_filters()
+   {
+   SymmetricKey key("00000000000000000000000000000000");
+
+   OCB_Encryption* ocb = new OCB_Encryption(new AES_128);
+
+   ocb->set_key(key);
+   Pipe pipe(ocb);
+
+   const std::vector<byte> empty;
+   std::vector<byte> N(12);
+   std::vector<byte> C;
+
+   for(size_t i = 0; i != 128; ++i)
+      {
+      const std::vector<byte> S(i);
+      N[11] = i;
+
+      const std::vector<byte> C1 = ocb_encrypt(*ocb, pipe, N, S, S);
+      const std::vector<byte> C2 = ocb_encrypt(*ocb, pipe, N, S, empty);
+      const std::vector<byte> C3 = ocb_encrypt(*ocb, pipe, N, empty, S);
+
+      //std::cout << "C_" << i << " = " << hex_encode(C1) << " " << hex_encode(C2) << " " << hex_encode(C3) << "\n";
+
+      C += C1;
+      C += C2;
+      C += C3;
+      }
+
+   SHA_256 sha256;
+   sha256.update(C);
+   const std::string C_hash = hex_encode(sha256.final());
+   const std::string expected_C_hash = "C4E5158067F49356042296B13B050DE00A120EA846073E5E0DACFD0C9F43CC65";
+
+   if(C_hash != expected_C_hash)
+      {
+      std::cout << "OCB-128 long test, C hashes differ\n";
+      std::cout << C_hash << " !=\n" << expected_C_hash << "\n";
+      }
+
+   //std::cout << "SHA-256(C) = " << C_hash << "\n";
+
+   N[11] = 0;
+   const std::vector<byte> cipher = ocb_encrypt(*ocb, pipe, N, empty, C);
+
+   const std::string expected = "B2B41CBF9B05037DA7F16C24A35C1C94";
+
+   const std::string cipher_hex = hex_encode(cipher);
+
+   if(cipher_hex != expected)
+      std::cout << "OCB AES-128 long test mistmatch " << cipher_hex << " != " << expected << "\n";
+   else
+      std::cout << "OCB AES-128 long test OK\n";
+   }
+
+void test_ocb_long()
+   {
+   SymmetricKey key("00000000000000000000000000000000");
+
+   const std::vector<byte> empty;
+   std::vector<byte> N(12);
+   std::vector<byte> C;
+
+   for(size_t i = 0; i != 128; ++i)
+      {
+      const std::vector<byte> S(i);
+      N[11] = i;
+
+      const std::vector<byte> C1 = ocb_encrypt(key, N, S, S);
+      const std::vector<byte> C2 = ocb_encrypt(key, N, S, empty);
+      const std::vector<byte> C3 = ocb_encrypt(key, N, empty, S);
+
+      //std::cout << "C_" << i << " = " << hex_encode(C1) << " " << hex_encode(C2) << " " << hex_encode(C3) << "\n";
+
+      C += C1;
+      C += C2;
+      C += C3;
+
+      SHA_256 sha256;
+      sha256.update(C);
+      //std::cout << "SHA-256(C_" << i << ") = " << hex_encode(sha256.final()) << "\n";
+      }
+
+   // SHA-256 hash of C would be useful
+
+   SHA_256 sha256;
+   sha256.update(C);
+   const std::string C_hash = hex_encode(sha256.final());
+   const std::string expected_C_hash = "C4E5158067F49356042296B13B050DE00A120EA846073E5E0DACFD0C9F43CC65";
+
+   if(C_hash != expected_C_hash)
+      {
+      std::cout << "OCB-128 long test, C hashes differ\n";
+      std::cout << C_hash << " !=\n" << expected_C_hash << "\n";
+      }
+
+   //std::cout << "SHA-256(C) = " << C_hash << "\n";
+
+   N[11] = 0;
+   const std::vector<byte> cipher = ocb_encrypt(key, N, empty, C);
+
+   const std::string expected = "B2B41CBF9B05037DA7F16C24A35C1C94";
+
+   const std::string cipher_hex = hex_encode(cipher);
+
+   if(cipher_hex != expected)
+      std::cout << "OCB AES-128 long test mistmatch " << cipher_hex << " != " << expected << "\n";
+   else
+      std::cout << "OCB AES-128 long test OK\n";
+
+   try
+      {
+      const std::vector<byte> p = ocb_decrypt(key, N, cipher, C);
+
+      BOTAN_ASSERT(p.empty(), "return plaintext is empty");
+      }
+   catch(std::exception& e)
+      {
+      std::cout << "Error in OCB decrypt - " << e.what() << "\n";
+      }
+
+   try
+      {
+      C[0] ^= 1;
+      ocb_decrypt(key, N, cipher, C);
+      std::cout << "OCB failed to reject bad message\n";
+      }
+   catch(std::exception& e)
+      {
+      }
+
+
+   }
+
+void test_ocb()
+   {
+   SymmetricKey key("000102030405060708090A0B0C0D0E0F");
+
+   std::vector<byte> nonce = hex_decode("000102030405060708090A0B");
+
+   std::vector<byte> pt = hex_decode("000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F2021222324252627");
+   std::vector<byte> ad = hex_decode("000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F2021222324252627");
+
+   const std::string expected = "BEA5E8798DBE7110031C144DA0B26122CEAAB9B05DF771A657149D53773463CB68C65778B058A635659C623211DEEA0DE30D2C381879F4C8";
+
+   std::vector<byte> ctext = ocb_encrypt(key, nonce, pt, ad);
+
+   const std::string ctext_hex = hex_encode(ctext);
+
+   if(ctext_hex != expected)
+      std::cout << "OCB/AES-128 encrypt test failure\n" << ctext_hex << " !=\n" << expected << "\n";
+   else
+      std::cout << "OCB/AES-128 encrypt OK\n";
+
+   try
+      {
+      std::vector<byte> dec = ocb_decrypt(key, nonce, ctext, ad);
+
+      if(dec == pt) { std::cout << "OCB decrypts OK\n"; }
+      else { std::cout << "OCB fails to decrypt\n"; }
+      }
+   catch(std::exception& e)
+      {
+      std::cout << "Correct OCB message rejected - " << e.what() << "\n";
+      }
+
+   //test_ocb_long();
+   test_ocb_long_filters();
+   }
+
+
diff --git a/checks/validate.cpp b/checks/validate.cpp
index 388d4940e..60fd729e3 100644
--- a/checks/validate.cpp
+++ b/checks/validate.cpp
@@ -416,6 +416,9 @@ u32bit do_validation_tests(const std::string& filename,
       errors++;
       }
 
+   if(should_pass)
+      test_ocb();
+
    return errors;
    }
 
diff --git a/checks/validate.dat b/checks/validate.dat
index f50b63547..2e748dfc7 100644
--- a/checks/validate.dat
+++ b/checks/validate.dat
@@ -25969,6 +25969,23 @@ F0F1F2F3F4F5F6F7F8F9FAFBFCFDFEFF
 603DEB1015CA71BE2B73AEF0857D77811F352C073B6108D72D9810A30914DFF4:\
 F0F1F2F3F4F5F6F7F8F9FAFBFCFDFEFF
 
+[AES-128/OCB]
+:197B9C3C441D3C83EAFB2BEF633B9182:\
+000102030405060708090A0B0C0D0E0F:000102030405060708090A0B
+
+0001020304050607:\
+92B657130A74B85A971EFFCAE19AD4716F88E87B871FBEED:\
+000102030405060708090A0B0C0D0E0F:000102030405060708090A0B
+
+000102030405060708090A0B0C0D0E0F:\
+BEA5E8798DBE7110031C144DA0B2612213CC8B747807121A4CBB3E4BD6B456AF:\
+000102030405060708090A0B0C0D0E0F:000102030405060708090A0B
+
+000102030405060708090A0B0C0D0E0F1011121314151617:\
+BEA5E8798DBE7110031C144DA0B26122FCFCEE7A\
+2A8D4D486EF2F52587FDA0ED97DC7EEDE241DF68:\
+000102030405060708090A0B0C0D0E0F:000102030405060708090A0B
+
 [AES-128/EAX]
 :32E55CE0C3FAEA48164B122C1BE22D85:\
 C61A0851AB4E515D11525B92E2B9D850:C825FC7C4D539DC74887CECC70884F37
diff --git a/checks/validate.h b/checks/validate.h
index b88837d4b..539154d53 100644
--- a/checks/validate.h
+++ b/checks/validate.h
@@ -30,4 +30,6 @@ void do_x509_tests(RandomNumberGenerator&);
 
 size_t do_tls_tests(RandomNumberGenerator& rng);
 
+void test_ocb();
+
 #endif
diff --git a/src/engine/core_engine/core_modes.cpp b/src/engine/core_engine/core_modes.cpp
index 21a5863e2..08124a3a0 100644
--- a/src/engine/core_engine/core_modes.cpp
+++ b/src/engine/core_engine/core_modes.cpp
@@ -40,6 +40,10 @@
   #include <botan/eax.h>
 #endif
 
+#if defined(BOTAN_HAS_OCB)
+  #include <botan/ocb.h>
+#endif
+
 #if defined(BOTAN_HAS_XTS)
   #include <botan/xts.h>
 #endif
@@ -127,6 +131,16 @@ Keyed_Filter* get_cipher_mode(const BlockCipher* block_cipher,
 #endif
       }
 
+#if defined(BOTAN_HAS_OCB)
+   if(mode == "OCB")
+      {
+      if(direction == ENCRYPTION)
+         return new OCB_Encryption(block_cipher->clone(), 16);
+      else
+         return new OCB_Decryption(block_cipher->clone(), 16);
+      }
+#endif
+
 #if defined(BOTAN_HAS_XTS)
    if(mode == "XTS")
       {
@@ -221,7 +235,10 @@ Keyed_Filter* Core_Engine::get_cipher(const std::string& algo_spec,
    if(filt)
       return filt;
 
-   throw Algorithm_Not_Found(cipher_name + "/" + mode + "/" + padding);
+   if(padding != "NoPadding")
+      throw Algorithm_Not_Found(cipher_name + "/" + mode + "/" + padding);
+   else
+      throw Algorithm_Not_Found(cipher_name + "/" + mode);
    }
 
 }
diff --git a/src/filters/modes/aead/aead.h b/src/filters/modes/aead/aead.h
new file mode 100644
index 000000000..868008e5d
--- /dev/null
+++ b/src/filters/modes/aead/aead.h
@@ -0,0 +1,38 @@
+/*
+* Interface for AEAD modes
+* (C) 2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_AEAD_H__
+#define BOTAN_AEAD_H__
+
+#include <botan/key_filt.h>
+
+namespace Botan {
+
+class AEAD_Mode : public Keyed_Filter
+   {
+   public:
+      /**
+      * Set associated data that is not included in the ciphertext but
+      * that should be authenticated. Must be called after set_key
+      * and before end_msg.
+      *
+      * @param ad the associated data
+      * @param ad_len length of add in bytes
+      */
+      virtual void set_associated_data(const byte ad[], size_t ad_len) = 0;
+
+      virtual void set_nonce(const byte nonce[], size_t nonce_len) = 0;
+
+      void set_iv(const InitializationVector& iv) override
+         {
+         set_nonce(iv.begin(), iv.length());
+         }
+   };
+
+}
+
+#endif
diff --git a/src/filters/modes/aead/info.txt b/src/filters/modes/aead/info.txt
new file mode 100644
index 000000000..b43aab2f6
--- /dev/null
+++ b/src/filters/modes/aead/info.txt
@@ -0,0 +1 @@
+define AEAD
diff --git a/src/filters/modes/ocb/info.txt b/src/filters/modes/ocb/info.txt
new file mode 100644
index 000000000..a98d7d54e
--- /dev/null
+++ b/src/filters/modes/ocb/info.txt
@@ -0,0 +1,7 @@
+define OCB
+
+<requires>
+block
+aead
+cmac
+</requires>
diff --git a/src/filters/modes/ocb/ocb.cpp b/src/filters/modes/ocb/ocb.cpp
new file mode 100644
index 000000000..a8481ab8a
--- /dev/null
+++ b/src/filters/modes/ocb/ocb.cpp
@@ -0,0 +1,381 @@
+/*
+* OCB Mode
+* (C) 2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/ocb.h>
+#include <botan/cmac.h>
+#include <botan/internal/xor_buf.h>
+#include <botan/internal/bit_ops.h>
+#include <algorithm>
+
+#include <botan/hex.h>
+#include <iostream>
+
+namespace Botan {
+
+// Has to be in Botan namespace so unique_ptr can reference it
+class L_computer
+   {
+   public:
+      L_computer(const BlockCipher& cipher)
+         {
+         m_L_star.resize(cipher.block_size());
+         cipher.encrypt(m_L_star);
+         m_L_dollar = poly_double(star());
+         m_L.push_back(poly_double(dollar()));
+         }
+
+      const secure_vector<byte>& star() const { return m_L_star; }
+
+      const secure_vector<byte>& dollar() const { return m_L_dollar; }
+
+      const secure_vector<byte>& operator()(size_t i) const { return get(i); }
+
+      const secure_vector<byte>& get(size_t i) const
+         {
+         while(m_L.size() <= i)
+            m_L.push_back(poly_double(m_L.back()));
+
+         return m_L.at(i);
+         }
+
+   private:
+      secure_vector<byte> poly_double(const secure_vector<byte>& in) const
+         {
+         return CMAC::poly_double(in, 0x87);
+         }
+
+      secure_vector<byte> m_L_dollar, m_L_star;
+      mutable std::vector<secure_vector<byte>> m_L;
+   };
+
+#if 0
+class Nonce_State
+   {
+   public:
+      secure_vector<byte> update_nonce(const byte nonce[], size_t nonce_len);
+
+      bool fresh_nonce() { bool b = false; std::swap(b, m_fresh); return b; }
+   private:
+      secure_vector<byte> m_stretch;
+      bool m_fresh = false;
+   };
+#endif
+
+namespace {
+
+/*
+* OCB's HASH
+*/
+secure_vector<byte> ocb_hash(const L_computer& L,
+                             const BlockCipher& cipher,
+                             const byte ad[], size_t ad_len)
+   {
+   const size_t BS = cipher.block_size();
+
+   secure_vector<byte> sum(BS);
+   secure_vector<byte> offset(BS);
+
+   secure_vector<byte> buf(BS);
+
+   const size_t ad_blocks = (ad_len / BS);
+   const size_t ad_remainder = (ad_len % BS);
+
+   for(size_t i = 0; i != ad_blocks; ++i)
+      {
+      // this loop could run in parallel
+      offset ^= L(ctz(i+1));
+
+      buf = offset;
+      xor_buf(&buf[0], &ad[BS*i], BS);
+
+      cipher.encrypt(buf);
+
+      sum ^= buf;
+      }
+
+   if(ad_remainder)
+      {
+      offset ^= L.star();
+
+      buf = offset;
+      xor_buf(&buf[0], &ad[BS*ad_blocks], ad_remainder);
+      buf[ad_len % BS] ^= 0x80;
+
+      cipher.encrypt(buf);
+
+      sum ^= buf;
+      }
+
+   return sum;
+   }
+
+}
+
+OCB_Mode::OCB_Mode(BlockCipher* cipher, size_t tag_size, bool decrypting) :
+   Buffered_Filter(cipher->parallel_bytes(), decrypting ? tag_size : 0),
+   m_cipher(cipher), m_tag_size(tag_size),
+   m_ad_hash(BS), m_offset(BS), m_checksum(BS)
+   {
+   if(m_cipher->block_size() != BS)
+      throw std::invalid_argument("OCB requires a 128 bit cipher so cannot be used with " +
+                                  m_cipher->name());
+
+   if(m_tag_size != 16) // 64, 96 bits also supported
+      throw std::invalid_argument("OCB cannot produce a " + std::to_string(m_tag_size) +
+                                  " byte tag");
+
+   }
+
+OCB_Mode::~OCB_Mode() { /* for unique_ptr destructor */ }
+
+bool OCB_Mode::valid_keylength(size_t n) const
+   {
+   return m_cipher->valid_keylength(n);
+   }
+
+std::string OCB_Mode::name() const
+   {
+   return m_cipher->name() + "/OCB"; // include tag size
+   }
+
+void OCB_Mode::set_key(const SymmetricKey& key)
+   {
+   m_cipher->set_key(key);
+   m_L.reset(new L_computer(*m_cipher));
+   }
+
+void OCB_Mode::set_nonce(const byte nonce[], size_t nonce_len)
+   {
+   if(!valid_iv_length(nonce_len))
+      throw Invalid_IV_Length(name(), nonce_len);
+
+   byte bottom;
+   secure_vector<byte> stretch;
+
+   if(1) // need to recompute stretch (save iv to compare)
+      {
+      secure_vector<byte> buf(BS);
+
+      const size_t offset = BS - nonce_len;
+
+      copy_mem(&buf[offset], nonce, nonce_len);
+      buf[offset-1] = 1;
+
+      bottom = buf[15] & 0x3F;
+      buf[15] &= 0xC0;
+
+      m_cipher->encrypt(buf);
+
+      for(size_t i = 0; i != 8; ++i)
+         buf.push_back(buf[i] ^ buf[i+1]);
+
+      stretch = buf;
+      }
+
+   // now set the offset from stretch and bottom
+
+   const size_t shift_bytes = bottom / 8;
+   const size_t shift_bits  = bottom % 8;
+
+   for(size_t i = 0; i != BS; ++i)
+      {
+      m_offset[i]  = (stretch[i+shift_bytes] << shift_bits);
+      m_offset[i] |= (stretch[i+shift_bytes+1] >> (8-shift_bits));
+      }
+   }
+
+void OCB_Mode::start_msg()
+   {
+   //BOTAN_ASSERT(m_nonce_state.fresh_nonce(), "Nonce state is fresh");
+   }
+
+void OCB_Mode::set_associated_data(const byte ad[], size_t ad_len)
+   {
+   m_ad_hash = ocb_hash(*m_L, *m_cipher, &ad[0], ad_len);
+   }
+
+void OCB_Mode::write(const byte input[], size_t length)
+   {
+   Buffered_Filter::write(input, length);
+   }
+
+void OCB_Mode::end_msg()
+   {
+   Buffered_Filter::end_msg();
+   }
+
+void OCB_Encryption::buffered_block(const byte input[], size_t input_length)
+   {
+   BOTAN_ASSERT(input_length % BS == 0, "Input length is an even number of blocks");
+
+   const size_t blocks = input_length / BS;
+
+#if 1
+   const size_t par_bytes = m_cipher->parallel_bytes();
+#else
+   const size_t par_bytes = 2*m_cipher->block_size();
+#endif
+
+   BOTAN_ASSERT(par_bytes % BS == 0, "Cipher is parallel in full blocks");
+
+   const size_t par_blocks = par_bytes / BS;
+
+   const L_computer& L = *m_L; // convenient name
+
+   secure_vector<byte> ctext_buf(BS);
+   secure_vector<byte> csum_accum(par_bytes);
+
+   size_t blocks_left = blocks;
+
+   while(blocks_left)
+      {
+      const size_t to_proc = std::min(blocks_left, par_blocks);
+      const size_t proc_bytes = to_proc * BS;
+
+      xor_buf(&csum_accum[0], &input[0], proc_bytes);
+
+      for(size_t i = 0; i != to_proc; ++i)
+         {
+         m_offset ^= L(ctz(++m_block_index));
+
+         ctext_buf = m_offset;
+         xor_buf(&ctext_buf[0], &input[BS*i], BS);
+         m_cipher->encrypt(ctext_buf);
+         ctext_buf ^= m_offset;
+
+         send(ctext_buf);
+         }
+
+      input += proc_bytes;
+      blocks_left -= to_proc;
+      }
+
+   // fold into checksum
+   for(size_t i = 0; i != csum_accum.size(); ++i)
+      m_checksum[i % BS] ^= csum_accum[i];
+   }
+
+void OCB_Encryption::buffered_final(const byte input[], size_t input_length)
+   {
+   if(input_length >= BS)
+      {
+      const size_t final_blocks = input_length / BS;
+      const size_t final_bytes = final_blocks * BS;
+      buffered_block(input, final_bytes);
+      input += final_bytes;
+      input_length -= final_bytes;
+      }
+
+   if(input_length)
+      {
+      BOTAN_ASSERT(input_length < BS, "Only a partial block left");
+
+      xor_buf(&m_checksum[0], &input[0], input_length);
+      m_checksum[input_length] ^= 0x80;
+
+      m_offset ^= m_L->star(); // Offset_*
+
+      secure_vector<byte> buf(BS);
+      m_cipher->encrypt(m_offset, buf);
+      xor_buf(&buf[0], &input[0], input_length);
+
+      send(buf, input_length); // final ciphertext
+      }
+
+   // now compute the tag
+   secure_vector<byte> mac = m_offset;
+   mac ^= m_checksum;
+   mac ^= m_L->dollar();
+
+   m_cipher->encrypt(mac);
+
+   mac ^= m_ad_hash;
+
+   send(mac);
+
+   zeroise(m_checksum);
+   zeroise(m_offset);
+   m_block_index = 0;
+   }
+
+void OCB_Decryption::buffered_block(const byte input[], size_t input_length)
+   {
+   BOTAN_ASSERT(input_length % BS == 0, "Input length is an even number of blocks");
+
+   const size_t blocks = input_length / BS;
+
+   const L_computer& L = *m_L;
+
+   secure_vector<byte> ptext_buf(BS);
+
+   for(size_t i = 0; i != blocks; ++i)
+      {
+      // could run in parallel
+
+      m_offset ^= L(ctz(++m_block_index));
+
+      ptext_buf = m_offset;
+      xor_buf(&ptext_buf[0], &input[BS*i], BS);
+      m_cipher->decrypt(ptext_buf);
+      ptext_buf ^= m_offset;
+
+      send(ptext_buf);
+      m_checksum ^= ptext_buf;
+      }
+   }
+
+void OCB_Decryption::buffered_final(const byte input[], size_t input_length)
+   {
+   BOTAN_ASSERT(input_length >= m_tag_size, "We have the tag");
+
+   const byte* included_tag = &input[input_length-m_tag_size];
+   input_length -= m_tag_size;
+
+   if(input_length >= BS)
+      {
+      const size_t final_blocks = input_length / BS;
+      const size_t final_bytes = final_blocks * BS;
+      buffered_block(input, final_bytes);
+      input += final_bytes;
+      input_length -= final_bytes;
+      }
+
+   if(input_length)
+      {
+      BOTAN_ASSERT(input_length < BS, "Only a partial block left");
+
+      m_offset ^= m_L->star(); // Offset_*
+
+      secure_vector<byte> buf(BS);
+      m_cipher->encrypt(m_offset, buf); // P_*
+
+      xor_buf(&buf[0], &input[0], input_length);
+
+      xor_buf(&m_checksum[0], &buf[0], input_length);
+      m_checksum[input_length] ^= 0x80;
+
+      send(buf, input_length); // final plaintext
+      }
+
+   // now compute the tag
+   secure_vector<byte> mac = m_offset;
+   mac ^= m_checksum;
+   mac ^= m_L->dollar();
+
+   m_cipher->encrypt(mac);
+
+   mac ^= m_ad_hash;
+
+   zeroise(m_checksum);
+   zeroise(m_offset);
+   m_block_index = 0;
+
+   if(!same_mem(&mac[0], included_tag, m_tag_size))
+      throw Integrity_Failure("OCB tag check failed");
+   }
+
+}
diff --git a/src/filters/modes/ocb/ocb.h b/src/filters/modes/ocb/ocb.h
new file mode 100644
index 000000000..5497b08a4
--- /dev/null
+++ b/src/filters/modes/ocb/ocb.h
@@ -0,0 +1,110 @@
+/*
+* OCB Mode
+* (C) 2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#ifndef BOTAN_OCB_H__
+#define BOTAN_OCB_H__
+
+#include <botan/aead.h>
+#include <botan/block_cipher.h>
+#include <botan/buf_filt.h>
+#include <memory>
+
+namespace Botan {
+
+class L_computer;
+//class Nonce_State;
+
+/**
+* OCB Mode (base class for OCB_Encryption and OCB_Decryption). Note
+* that OCB is patented, but is freely licensed in some circumstances.
+*
+* @see "The OCB Authenticated-Encryption Algorithm" internet draft
+        http://tools.ietf.org/html/draft-irtf-cfrg-ocb-00
+* @see Free Licenses http://www.cs.ucdavis.edu/~rogaway/ocb/license.htm
+* @see OCB home page http://www.cs.ucdavis.edu/~rogaway/ocb
+*/
+class BOTAN_DLL OCB_Mode : public AEAD_Mode,
+                           private Buffered_Filter
+   {
+   public:
+      void set_key(const SymmetricKey& key) override;
+
+      void set_nonce(const byte nonce[], size_t nonce_len) override;
+
+      void set_associated_data(const byte ad[], size_t ad_len) override;
+
+      bool valid_keylength(size_t n) const override;
+
+      std::string name() const override;
+
+      bool valid_iv_length(size_t length) const override
+         {
+         return (length > 0 && length < 16);
+         }
+
+      ~OCB_Mode();
+
+   protected:
+      /**
+      * @param cipher the 128-bit block cipher to use
+      * @param tag_size is how big the auth tag will be
+      * @param decrypting  true if decrypting
+      */
+      OCB_Mode(BlockCipher* cipher, size_t tag_size, bool decrypting);
+
+      static const size_t BS = 16; // intrinsic to OCB definition
+
+      // fixme make these private
+      std::unique_ptr<BlockCipher> m_cipher;
+      std::unique_ptr<L_computer> m_L;
+
+      size_t m_tag_size = 0;
+      size_t m_block_index = 0;
+
+      secure_vector<byte> m_ad_hash;
+      secure_vector<byte> m_offset;
+      secure_vector<byte> m_checksum;
+
+   private:
+      void write(const byte input[], size_t input_length) override;
+      void start_msg() override;
+      void end_msg() override;
+   };
+
+class BOTAN_DLL OCB_Encryption : public OCB_Mode
+   {
+   public:
+      /**
+      * @param cipher the 128-bit block cipher to use
+      * @param tag_size is how big the auth tag will be
+      */
+      OCB_Encryption(BlockCipher* cipher, size_t tag_size = 16) :
+         OCB_Mode(cipher, tag_size, false) {}
+
+   private:
+      void buffered_block(const byte input[], size_t input_length) override;
+      void buffered_final(const byte input[], size_t input_length) override;
+   };
+
+class BOTAN_DLL OCB_Decryption : public OCB_Mode
+   {
+   public:
+      /**
+      * @param cipher the 128-bit block cipher to use
+      * @param tag_size is how big the auth tag will be
+      */
+      OCB_Decryption(BlockCipher* cipher, size_t tag_size = 16) :
+         OCB_Mode(cipher, tag_size, true) {}
+
+   private:
+      void buffered_block(const byte input[], size_t input_length) override;
+      void buffered_final(const byte input[], size_t input_length) override;
+   };
+
+}
+
+#endif
diff --git a/src/utils/xor_buf.h b/src/utils/xor_buf.h
index b67d84c50..5773a619c 100644
--- a/src/utils/xor_buf.h
+++ b/src/utils/xor_buf.h
@@ -96,6 +96,18 @@ void xor_buf(std::vector<byte, Alloc>& out,
    xor_buf(&out[0], &in[0], &in2[0], n);
    }
 
+template<typename T, typename Alloc, typename Alloc2>
+std::vector<T, Alloc>&
+operator^=(std::vector<T, Alloc>& out,
+           const std::vector<T, Alloc2>& in)
+   {
+   if(out.size() < in.size())
+      out.resize(in.size());
+
+   xor_buf(&out[0], &in[0], in.size());
+   return out;
+   }
+
 }
 
 #endif