Botan  1.11.15
Public Types | Public Member Functions | Protected Member Functions
Botan::XTS_Decryption Class Reference

#include <xts.h>

Inheritance diagram for Botan::XTS_Decryption:
Botan::XTS_Mode Botan::Cipher_Mode Botan::Keyed_Transform Botan::Transform

List of all members.

Public Types

typedef SCAN_Name Spec

Public Member Functions

virtual bool authenticated () const
void clear () override
size_t default_nonce_length () const override
void finish (secure_vector< byte > &final_block, size_t offset=0) override
Key_Length_Specification key_spec () const override
size_t minimum_final_size () const override
std::string name () const override
size_t output_length (size_t input_length) const override
virtual std::string provider () const
template<typename Alloc >
void set_key (const std::vector< byte, Alloc > &key)
void set_key (const SymmetricKey &key)
void set_key (const byte key[], size_t length)
template<typename Alloc >
secure_vector< bytestart (const std::vector< byte, Alloc > &nonce)
secure_vector< bytestart (const byte nonce[], size_t nonce_len)
secure_vector< bytestart ()
template<typename Alloc >
secure_vector< bytestart_vec (const std::vector< byte, Alloc > &nonce)
virtual size_t tag_size () const
void update (secure_vector< byte > &blocks, size_t offset=0) override
size_t update_granularity () const override
bool valid_keylength (size_t length) const
bool valid_nonce_length (size_t n) const override
 XTS_Decryption (BlockCipher *cipher)

Protected Member Functions

const BlockCiphercipher () const
const bytetweak () const
void update_tweak (size_t last_used)

Detailed Description

IEEE P1619 XTS Decryption

Definition at line 70 of file xts.h.


Member Typedef Documentation

typedef SCAN_Name Botan::Transform::Spec [inherited]

Definition at line 27 of file transform.h.


Constructor & Destructor Documentation

Definition at line 73 of file xts.h.


Member Function Documentation

virtual bool Botan::Cipher_Mode::authenticated ( ) const [inline, virtual, inherited]

Returns true iff this mode provides authentication as well as confidentiality.

Reimplemented in Botan::AEAD_Mode.

Definition at line 26 of file cipher_mode.h.

{ return false; }
const BlockCipher& Botan::XTS_Mode::cipher ( ) const [inline, protected, inherited]
void Botan::XTS_Mode::clear ( ) [override, virtual, inherited]

Implements Botan::Transform.

Definition at line 62 of file xts.cpp.

References Botan::zeroise().

   {
   m_cipher->clear();
   m_tweak_cipher->clear();
   zeroise(m_tweak);
   }
size_t Botan::XTS_Mode::default_nonce_length ( ) const [override, virtual, inherited]

Return the default size for a nonce

Implements Botan::Transform.

Definition at line 89 of file xts.cpp.

References Botan::BlockCipher::block_size(), and Botan::XTS_Mode::cipher().

   {
   return cipher().block_size();
   }
void Botan::XTS_Decryption::finish ( secure_vector< byte > &  final_block,
size_t  offset = 0 
) [override, virtual]

Complete processing of a message.

Parameters:
final_blockin/out parameter which must be at least minimum_final_size() bytes, and will be set to any final output
offsetan offset into final_block to begin processing

Implements Botan::Transform.

Definition at line 249 of file xts.cpp.

References Botan::BlockCipher::block_size(), BOTAN_ASSERT, Botan::XTS_Mode::cipher(), Botan::BlockCipher::decrypt(), Botan::XTS_Mode::minimum_final_size(), Botan::XTS_Mode::tweak(), update(), and Botan::xor_buf().

   {
   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
   const size_t sz = buffer.size() - offset;
   byte* buf = &buffer[offset];

   BOTAN_ASSERT(sz >= minimum_final_size(), "Have sufficient final input");

   const size_t BS = cipher().block_size();

   if(sz % BS == 0)
      {
      update(buffer, offset);
      }
   else
      {
      // steal ciphertext
      const size_t full_blocks = ((sz / BS) - 1) * BS;
      const size_t final_bytes = sz - full_blocks;
      BOTAN_ASSERT(final_bytes > BS && final_bytes < 2*BS, "Left over size in expected range");

      secure_vector<byte> last(buf + full_blocks, buf + full_blocks + final_bytes);
      buffer.resize(full_blocks + offset);
      update(buffer, offset);

      xor_buf(last, tweak() + BS, BS);
      cipher().decrypt(last);
      xor_buf(last, tweak() + BS, BS);

      for(size_t i = 0; i != final_bytes - BS; ++i)
         {
         last[i] ^= last[i + BS];
         last[i + BS] ^= last[i];
         last[i] ^= last[i + BS];
         }

      xor_buf(last, tweak(), BS);
      cipher().decrypt(last);
      xor_buf(last, tweak(), BS);

      buffer += last;
      }
   }
Key_Length_Specification Botan::XTS_Mode::key_spec ( ) const [override, virtual, inherited]
Returns:
object describing limits on key size

Implements Botan::Keyed_Transform.

Definition at line 84 of file xts.cpp.

References Botan::XTS_Mode::cipher(), Botan::SymmetricAlgorithm::key_spec(), and Botan::Key_Length_Specification::multiple().

   {
   return cipher().key_spec().multiple(2);
   }
size_t Botan::XTS_Mode::minimum_final_size ( ) const [override, virtual, inherited]
Returns:
required minimium size to finalize() - may be any length larger than this.

Implements Botan::Transform.

Definition at line 79 of file xts.cpp.

References Botan::BlockCipher::block_size(), and Botan::XTS_Mode::cipher().

Referenced by Botan::XTS_Encryption::finish(), and finish().

   {
   return cipher().block_size() + 1;
   }
std::string Botan::XTS_Mode::name ( ) const [override, virtual, inherited]

Implements Botan::Transform.

Definition at line 69 of file xts.cpp.

References Botan::XTS_Mode::cipher(), and Botan::SymmetricAlgorithm::name().

   {
   return cipher().name() + "/XTS";
   }
size_t Botan::XTS_Decryption::output_length ( size_t  input_length) const [override, virtual]

Returns the size of the output if this transform is used to process a message with input_length bytes. Will throw if unable to give a precise answer.

Implements Botan::Transform.

Definition at line 214 of file xts.cpp.

   {
   // might be less
   return input_length;
   }
virtual std::string Botan::Transform::provider ( ) const [inline, virtual, inherited]

Return some short name describing the provider of this tranformation. Useful in cases where multiple implementations are available (eg, different implementations of AES). Default "core" is used for the 'standard' implementation included in the library.

Definition at line 120 of file transform.h.

{ return "core"; }
template<typename Alloc >
void Botan::Keyed_Transform::set_key ( const std::vector< byte, Alloc > &  key) [inline, inherited]

Definition at line 148 of file transform.h.

Referenced by botan_cipher_set_key().

         {
         set_key(&key[0], key.size());
         }
void Botan::Keyed_Transform::set_key ( const SymmetricKey key) [inline, inherited]

Definition at line 153 of file transform.h.

References Botan::OctetString::begin(), and Botan::OctetString::length().

         {
         set_key(key.begin(), key.length());
         }
void Botan::Keyed_Transform::set_key ( const byte  key[],
size_t  length 
) [inline, inherited]

Set the symmetric key of this transform

Parameters:
keycontains the key material
lengthin bytes of key param

Definition at line 163 of file transform.h.

         {
         if(!valid_keylength(length))
            throw Invalid_Key_Length(name(), length);
         key_schedule(key, length);
         }
template<typename Alloc >
secure_vector<byte> Botan::Transform::start ( const std::vector< byte, Alloc > &  nonce) [inline, inherited]

Begin processing a message.

Parameters:
noncethe per message nonce

Definition at line 34 of file transform.h.

Referenced by botan_cipher_start().

         {
         return start(&nonce[0], nonce.size());
         }
secure_vector<byte> Botan::Transform::start ( const byte  nonce[],
size_t  nonce_len 
) [inline, inherited]

Begin processing a message.

Parameters:
noncethe per message nonce
nonce_lenlength of nonce

Definition at line 55 of file transform.h.

         {
         return start_raw(nonce, nonce_len);
         }
secure_vector<byte> Botan::Transform::start ( ) [inline, inherited]

Begin processing a message.

Definition at line 63 of file transform.h.

         {
         return start_raw(nullptr, 0);
         }
template<typename Alloc >
secure_vector<byte> Botan::Transform::start_vec ( const std::vector< byte, Alloc > &  nonce) [inline, inherited]

Begin processing a message.

Parameters:
noncethe per message nonce

Definition at line 45 of file transform.h.

         {
         return start(&nonce[0], nonce.size());
         }
virtual size_t Botan::Cipher_Mode::tag_size ( ) const [inline, virtual, inherited]

Return the size of the authentication tag used (in bytes)

Reimplemented in Botan::SIV_Mode, Botan::CCM_Mode, Botan::OCB_Mode, Botan::ChaCha20Poly1305_Mode, Botan::GCM_Mode, and Botan::EAX_Mode.

Definition at line 31 of file cipher_mode.h.

Referenced by botan_cipher_get_tag_length().

{ return 0; }
const byte* Botan::XTS_Mode::tweak ( ) const [inline, protected, inherited]

Definition at line 38 of file xts.h.

Referenced by Botan::XTS_Encryption::finish(), finish(), Botan::XTS_Encryption::update(), and update().

{ return &m_tweak[0]; }
void Botan::XTS_Decryption::update ( secure_vector< byte > &  blocks,
size_t  offset = 0 
) [override, virtual]

Process some data. Input must be in size update_granularity() byte blocks.

Parameters:
blocksin/out paramter which will possibly be resized
offsetan offset into blocks to begin processing

Implements Botan::Transform.

Definition at line 220 of file xts.cpp.

References Botan::BlockCipher::block_size(), BOTAN_ASSERT, Botan::XTS_Mode::cipher(), Botan::BlockCipher::decrypt_n(), Botan::XTS_Mode::tweak(), Botan::XTS_Mode::update_granularity(), Botan::XTS_Mode::update_tweak(), and Botan::xor_buf().

Referenced by finish().

   {
   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
   const size_t sz = buffer.size() - offset;
   byte* buf = &buffer[offset];

   const size_t BS = cipher().block_size();

   BOTAN_ASSERT(sz % BS == 0, "Input is full blocks");
   size_t blocks = sz / BS;

   const size_t blocks_in_tweak = update_granularity() / BS;

   while(blocks)
      {
      const size_t to_proc = std::min(blocks, blocks_in_tweak);
      const size_t to_proc_bytes = to_proc * BS;

      xor_buf(buf, tweak(), to_proc_bytes);
      cipher().decrypt_n(buf, buf, to_proc);
      xor_buf(buf, tweak(), to_proc_bytes);

      buf += to_proc * BS;
      blocks -= to_proc;

      update_tweak(to_proc);
      }
   }
size_t Botan::XTS_Mode::update_granularity ( ) const [override, virtual, inherited]
Returns:
size of required blocks to update

Implements Botan::Transform.

Definition at line 74 of file xts.cpp.

References Botan::XTS_Mode::cipher(), and Botan::BlockCipher::parallel_bytes().

Referenced by Botan::XTS_Encryption::update(), update(), Botan::XTS_Mode::update_tweak(), and Botan::XTS_Mode::XTS_Mode().

   {
   return cipher().parallel_bytes();
   }
void Botan::XTS_Mode::update_tweak ( size_t  last_used) [protected, inherited]

Definition at line 123 of file xts.cpp.

References Botan::XTS_Mode::update_granularity().

Referenced by Botan::XTS_Encryption::update(), and update().

   {
   const size_t BS = m_tweak_cipher->block_size();

   if(which > 0)
      poly_double(&m_tweak[0], &m_tweak[(which-1)*BS], BS);

   const size_t blocks_in_tweak = update_granularity() / BS;

   for(size_t i = 1; i < blocks_in_tweak; ++i)
      poly_double(&m_tweak[i*BS], &m_tweak[(i-1)*BS], BS);
   }
bool Botan::Keyed_Transform::valid_keylength ( size_t  length) const [inline, inherited]

Check whether a given key length is valid for this algorithm.

Parameters:
lengththe key length to be checked.
Returns:
true if the key length is valid.

Definition at line 142 of file transform.h.

References Botan::Key_Length_Specification::valid_keylength().

         {
         return key_spec().valid_keylength(length);
         }
bool Botan::XTS_Mode::valid_nonce_length ( size_t  nonce_len) const [override, virtual, inherited]

Return true iff nonce_len is a valid length for the nonce

Implements Botan::Transform.

Definition at line 94 of file xts.cpp.

References Botan::BlockCipher::block_size(), Botan::XTS_Mode::cipher(), and n.

   {
   return cipher().block_size() == n;
   }

The documentation for this class was generated from the following files: