keypair.cpp

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/*
* Keypair Checks
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
 
#include <botan/keypair.h>
#include <botan/pubkey.h>
 
namespace Botan {
 
namespace KeyPair {
 
/*
* Check an encryption key pair for consistency
*/
bool encryption_consistency_check(RandomNumberGenerator& rng,
                                  const Private_Key& key,
                                  const std::string& padding)
   {
   PK_Encryptor_EME encryptor(key, padding);
   PK_Decryptor_EME decryptor(key, padding);
 
   /*
   Weird corner case, if the key is too small to encrypt anything at
   all. This can happen with very small RSA keys with PSS
   */
   if(encryptor.maximum_input_size() == 0)
      return true;
 
   SecureVector<byte> plaintext =
      rng.random_vec(encryptor.maximum_input_size() - 1);
 
   SecureVector<byte> ciphertext = encryptor.encrypt(plaintext, rng);
   if(ciphertext == plaintext)
      return false;
 
   SecureVector<byte> decrypted = decryptor.decrypt(ciphertext);
 
   return (plaintext == decrypted);
   }
 
/*
* Check a signature key pair for consistency
*/
bool signature_consistency_check(RandomNumberGenerator& rng,
                                 const Private_Key& key,
                                 const std::string& padding)
   {
   PK_Signer signer(key, padding);
   PK_Verifier verifier(key, padding);
 
   SecureVector<byte> message = rng.random_vec(16);
 
   SecureVector<byte> signature;
 
   try
      {
      signature = signer.sign_message(message, rng);
      }
   catch(Encoding_Error)
      {
      return false;
      }
 
   if(!verifier.verify_message(message, signature))
      return false;
 
   // Now try to check a corrupt signature, ensure it does not succeed
   ++message[0];
 
   if(verifier.verify_message(message, signature))
      return false;
 
   return true;
   }
 
}
 
}