Botan::DSA_Signature_Operation Class Reference

#include <dsa.h>

Inheritance diagram for Botan::DSA_Signature_Operation:

Public Member Functions
	DSA_Signature_Operation (const DSA_PrivateKey &dsa)
size_t	max_input_bits () const
size_t	message_part_size () const
size_t	message_parts () const
SecureVector< byte >	sign (const byte msg[], size_t msg_len, RandomNumberGenerator &rng)

Detailed Description

Object that can create a DSA signature

Definition at line 63 of file dsa.h.

Constructor & Destructor Documentation

DSA_Signature_Operation()

Botan::DSA_Signature_Operation::DSA_Signature_Operation

(

const DSA_PrivateKey &

dsa

)

Definition at line 68 of file dsa.cpp.

                                                                          :
   q(dsa.group_q()),
   x(dsa.get_x()),
   powermod_g_p(dsa.group_g(), dsa.group_p()),
   mod_q(dsa.group_q())
   {
   }

Referenced by Botan::Core_Engine::get_signature_op().

Member Function Documentation

max_input_bits()

size_t Botan::DSA_Signature_Operation::max_input_bits ( ) const

inlinevirtual

Get the maximum message size in bits supported by this public key.

Returns

maximum message in bits

Implements Botan::PK_Ops::Signature.

Definition at line 70 of file dsa.h.

{ return q.bits(); }

message_part_size()

size_t Botan::DSA_Signature_Operation::message_part_size ( ) const

inlinevirtual

Find out the message part size supported by this scheme/key.

Returns

size of the message parts

Reimplemented from Botan::PK_Ops::Signature.

Definition at line 69 of file dsa.h.

{ return q.bytes(); }

message_parts()

size_t Botan::DSA_Signature_Operation::message_parts ( ) const

inlinevirtual

Find out the number of message parts supported by this scheme.

Returns

number of message parts

Reimplemented from Botan::PK_Ops::Signature.

Definition at line 68 of file dsa.h.

{ return 2; }

sign()

SecureVector< byte > Botan::DSA_Signature_Operation::sign ( const byte msg[], size_t msg_len, RandomNumberGenerator & rng )

virtual

Implements Botan::PK_Ops::Signature.

Definition at line 77 of file dsa.cpp.

   {
   rng.add_entropy(msg, msg_len);
 
   BigInt i(msg, msg_len);
   BigInt r = 0, s = 0;
 
   while(r == 0 || s == 0)
      {
      BigInt k;
      do
         k.randomize(rng, q.bits());
      while(k >= q);
 
      r = mod_q.reduce(powermod_g_p(k));
      s = mod_q.multiply(inverse_mod(k, q), mul_add(x, r, i));
      }
 
   SecureVector<byte> output(2*q.bytes());
   r.binary_encode(&output[output.size() / 2 - r.bytes()]);
   s.binary_encode(&output[output.size() - s.bytes()]);
   return output;
   }

References Botan::RandomNumberGenerator::add_entropy(), Botan::BigInt::binary_encode(), Botan::BigInt::bytes(), Botan::inverse_mod(), Botan::mul_add(), Botan::BigInt::randomize(), and Botan::MemoryRegion< T >::size().

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

• src/pubkey/dsa/dsa.h
• src/pubkey/dsa/dsa.cpp