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#pike __REAL_VERSION__ 
#pragma strict_types 
 
//! Base class for block cipher algorithms. 
//! 
//! Implements some common convenience functions, and prototypes. 
//! 
//! It also implements operating modes other than ECB. 
//! 
//! Note that no actual cipher algorithm is implemented 
//! in the base class. They are implemented in classes 
//! that inherit this class. 
 
inherit .Cipher; 
 
//! @module CTR 
//! Implementation of Counter Mode (CTR). Works as 
//! a wrapper for the cipher algorithm in the parent module. 
//! 
//! This cipher mode works like a stream cipher with 
//! a block size >= 1. This means that the same key 
//! and initialization vector (aka counter) should 
//! never be reused, since a simple xor would reveal 
//! information about the plain text. It also means 
//! that it should never be used without a suiteable 
//! Message Authentication Code (MAC). 
//! 
//! @seealso 
//!   @[predef::Nettle.BlockCipher.CBC], @[predef::Nettle.BlockCipher.CCM], 
//!   @[predef::Nettle.BlockCipher.GCM], @[MAC] 
 
//! @ignore 
protected class _CTR 
{ 
  //! @endignore 
 
  inherit .Cipher; 
 
  //! Returns the name of the base cipher extended with @expr{".CTR"@}. 
  string(7bit) name() 
  { 
    return global::name() + ".CTR"; 
  } 
 
  //! The state for the embedded algorithm 
  class State 
  { 
    inherit ::this_program; 
 
    protected zero|global::State obj; 
    protected zero|Gmp.mpz iv; 
    protected int(0..) _block_size; 
 
    protected void create() 
    { 
      obj = global::State(); 
      _block_size = obj->block_size(); 
      iv = Gmp.mpz(0); 
    } 
 
    string(8bit) name() 
    { 
      return obj->name() + ".CTR"; 
    } 
 
    int(1..) block_size() 
    { 
      return [int(1..)]_block_size; 
    } 
 
    int(1..) iv_size() 
    { 
      return [int(1..)]_block_size; 
    } 
 
    int(0..) key_size() 
    { 
      return obj->key_size(); 
    } 
 
    this_program set_encrypt_key(string(8bit) key, int|void flags) 
    { 
      String.secure(key); 
      obj->set_encrypt_key(key, flags); 
      return this; 
    } 
 
    this_program set_decrypt_key(string(8bit) key, int|void flags) 
    { 
      String.secure(key); 
      obj->set_encrypt_key(key, flags); 
      return this; 
    } 
 
    this_program set_iv(string(8bit) iv) 
    { 
      String.secure(iv); 
      this::iv = Gmp.mpz(iv, 256); 
    } 
 
    string(8bit) crypt(string(8bit) data) 
    { 
      int len = sizeof(data); 
      String.Buffer buf = String.Buffer(len); 
      while (len > 0) { 
        string(8bit) chunk = iv->digits(256); 
        iv++; 
        if (sizeof(chunk) < _block_size) { 
          chunk = "\0"*(_block_size - sizeof(chunk)) + chunk; 
        } 
        chunk = obj->crypt(chunk); 
        buf->add(chunk[..len-1]); 
        len -= _block_size; 
      } 
      return [string(8bit)](data ^ (string(8bit))buf); 
    } 
  } 
 
  protected State `()() 
  { 
    return State(); 
  } 
 
  //! @ignore 
} 
 
_CTR CTR = _CTR(); 
//! @endignore