Botan::CTR_BE Class Reference

#include <ctr.h>

Inheritance diagram for Botan::CTR_BE:

Public Member Functions
void	cipher (const byte in[], byte out[], size_t length)
void	cipher1 (byte buf[], size_t len)
void	clear ()
CTR_BE *	clone () const
	CTR_BE (BlockCipher *cipher)
Key_Length_Specification	key_spec () const
size_t	maximum_keylength () const
size_t	minimum_keylength () const
std::string	name () const
void	set_iv (const byte iv[], size_t iv_len)
void	set_key (const byte key[], size_t length)
void	set_key (const SymmetricKey &key)
bool	valid_iv_length (size_t iv_len) const
bool	valid_keylength (size_t length) const
	~CTR_BE ()

Detailed Description

CTR-BE (Counter mode, big-endian)

Definition at line 19 of file ctr.h.

Constructor & Destructor Documentation

CTR_BE()

Botan::CTR_BE::CTR_BE

(

BlockCipher *

cipher

)

Parameters

cipher

the underlying block cipher to use

Definition at line 17 of file ctr.cpp.

                                :
   permutation(ciph),
   counter(256 * permutation->block_size()),
   buffer(counter.size()),
   position(0)
   {
   }

Referenced by Botan::aont_package(), Botan::aont_unpackage(), clone(), Botan::EAX_Base::EAX_Base(), and Botan::get_cipher_mode().

~CTR_BE()

Botan::CTR_BE::~CTR_BE

(

)

Definition at line 28 of file ctr.cpp.

   {
   delete permutation;
   }

Member Function Documentation

cipher()

void Botan::CTR_BE::cipher ( const byte in[], byte out[], size_t len )

virtual

Encrypt or decrypt a message

Parameters

in	the plaintext
out	the byte array to hold the output, i.e. the ciphertext
len	the length of both in and out in bytes

Implements Botan::StreamCipher.

Definition at line 66 of file ctr.cpp.

   {
   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;
   }

References Botan::xor_buf().

cipher1()

void Botan::StreamCipher::cipher1 ( byte buf[], size_t len )

inlineinherited

Encrypt or decrypt a message

Parameters

buf	the plaintext / ciphertext
len	the length of buf in bytes

Definition at line 34 of file stream_cipher.h.

         { cipher(buf, buf, len); }

References cipher().

clear()

void Botan::CTR_BE::clear ( )

virtual

Zeroize internal state

Implements Botan::Algorithm.

Definition at line 36 of file ctr.cpp.

   {
   permutation->clear();
   zeroise(buffer);
   zeroise(counter);
   position = 0;
   }

References Botan::zeroise().

clone()

CTR_BE * Botan::CTR_BE::clone ( ) const

inlinevirtual

Get a new object representing the same algorithm as *this

Implements Botan::StreamCipher.

Definition at line 36 of file ctr.h.

         { return new CTR_BE(permutation->clone()); }

References CTR_BE().

key_spec()

Key_Length_Specification Botan::CTR_BE::key_spec ( ) const

inlinevirtual

Returns

object describing limits on key size

Implements Botan::SymmetricAlgorithm.

Definition at line 29 of file ctr.h.

         {
         return permutation->key_spec();
         }

maximum_keylength()

size_t Botan::SymmetricAlgorithm::maximum_keylength ( ) const

inlineinherited

Returns

minimum allowed key length

Definition at line 33 of file sym_algo.h.

         {
         return key_spec().maximum_keylength();
         }

References key_spec().

minimum_keylength()

size_t Botan::SymmetricAlgorithm::minimum_keylength ( ) const

inlineinherited

Returns

maxmium allowed key length

Definition at line 41 of file sym_algo.h.

         {
         return key_spec().minimum_keylength();
         }

References key_spec().

name()

std::string Botan::CTR_BE::name ( ) const

virtual

Returns

name of this algorithm

Implements Botan::Algorithm.

Definition at line 58 of file ctr.cpp.

   {
   return ("CTR-BE(" + permutation->name() + ")");
   }

Referenced by set_iv().

set_iv()

void Botan::CTR_BE::set_iv ( const byte iv[], size_t iv_len )

virtual

Resync the cipher using the IV

Parameters

iv	the initialization vector
iv_len	the length of the IV in bytes

Reimplemented from Botan::StreamCipher.

Definition at line 83 of file ctr.cpp.

   {
   if(!valid_iv_length(iv_len))
      throw Invalid_IV_Length(name(), iv_len);
 
   const size_t bs = permutation->block_size();
 
   zeroise(counter);
 
   counter.copy(0, iv, iv_len);
 
   /*
   * Set counter blocks to IV, IV + 1, ... IV + 255
   */
   for(size_t i = 1; i != 256; ++i)
      {
      counter.copy(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;
   }

References Botan::Invalid_IV_Length::Invalid_IV_Length(), name(), valid_iv_length(), and Botan::zeroise().

set_key() [1/2]

void Botan::SymmetricAlgorithm::set_key ( const byte key[], size_t length )

inlineinherited

Set the symmetric key of this object.

Parameters

key	the to be set as a byte array.
length	in bytes of key param

Definition at line 68 of file sym_algo.h.

         {
         if(!valid_keylength(length))
            throw Invalid_Key_Length(name(), length);
         key_schedule(key, length);
         }

References Botan::Algorithm::name(), and valid_keylength().

set_key() [2/2]

void Botan::SymmetricAlgorithm::set_key ( const SymmetricKey & key )

inlineinherited

Set the symmetric key of this object.

Parameters

key	the SymmetricKey to be set.

Definition at line 60 of file sym_algo.h.

         { set_key(key.begin(), key.length()); }

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

Referenced by Botan::aont_package(), Botan::aont_unpackage(), Botan::MAC_Filter::MAC_Filter(), Botan::MAC_Filter::MAC_Filter(), Botan::EAX_Base::set_key(), set_key(), Botan::Record_Reader::set_keys(), Botan::Record_Writer::set_keys(), Botan::StreamCipher_Filter::StreamCipher_Filter(), and Botan::StreamCipher_Filter::StreamCipher_Filter().

valid_iv_length()

bool Botan::CTR_BE::valid_iv_length ( size_t iv_len ) const

inlinevirtual

Parameters

iv_len

the length of the IV in bytes

Returns

if the length is valid for this algorithm

Reimplemented from Botan::StreamCipher.

Definition at line 26 of file ctr.h.

         { return (iv_len <= permutation->block_size()); }

Referenced by set_iv().

valid_keylength()

bool Botan::SymmetricAlgorithm::valid_keylength ( size_t length ) const

inlineinherited

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

Parameters

length

the key length to be checked.

Returns

true if the key length is valid.

Definition at line 51 of file sym_algo.h.

         {
         return key_spec().valid_keylength(length);
         }

References key_spec().

Referenced by Botan::aont_package(), Botan::aont_unpackage(), set_key(), and Botan::EAX_Base::valid_keylength().

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

• src/stream/ctr/ctr.h
• src/stream/ctr/ctr.cpp