Crypto ++ symmetric algorithms and combinations of authenticated block modes

Question

I implemented the C ++ cover library for Crypto ++ v5.6.2 and asked a question about combinations of symmetric algorithms (like Blowfish) and a block (like GCM).

I can encrypt and decrypt data through Blowfish / EAX, but I cannot achieve this using Blowfish / GCM. AES / EAX and AES / GCM work.

The following simple application demonstrates my problem:

#include <iostream>
#include <string>

#include "cryptopp/blowfish.h"
#include "cryptopp/filters.h"
#include "cryptopp/eax.h"
#include "cryptopp/gcm.h"
#include "cryptopp/osrng.h"
#include "cryptopp/hex.h"

std::string encrypt(
    CryptoPP::AuthenticatedSymmetricCipher &encryption,
    std::string const kPlainText,
    CryptoPP::SecByteBlock const kKey,
    unsigned const char * kIV) {
  std::string cipher_text;

  // TODO Is this the source of the problem?
  // BlockSize always returns 0 which leads to an exception if GCM block mode is used!
  std::cout << encryption.BlockSize() << " bytes" << std::endl;

  encryption.SetKeyWithIV(
      kKey,
      kKey.size(),
      kIV
  );

  CryptoPP::StringSink *string_sink = new CryptoPP::StringSink(cipher_text);
  CryptoPP::BufferedTransformation *transformator = NULL;

  // The AuthenticatedEncryptionFilter adds padding as required.
  transformator = new CryptoPP::AuthenticatedEncryptionFilter(
      encryption,
      string_sink);

  bool const kPumpAll = true;
  CryptoPP::StringSource(
      kPlainText,
      kPumpAll,
      transformator);

  return cipher_text;
}

std::string decrypt(
    CryptoPP::AuthenticatedSymmetricCipher &decryption,
    std::string const kCipherText,
    CryptoPP::SecByteBlock const kKey,
    unsigned const char * kIV) {
  std::string recovered_plain_text;

  decryption.SetKeyWithIV(
      kKey,
      kKey.size(),
      kIV);

  CryptoPP::StringSink *string_sink = new CryptoPP::StringSink(
      recovered_plain_text);
  CryptoPP::BufferedTransformation *transformator = NULL;
  CryptoPP::AuthenticatedDecryptionFilter *decryption_filter = NULL;

  decryption_filter = new CryptoPP::AuthenticatedDecryptionFilter(
      decryption,
      string_sink);
  transformator = new CryptoPP::Redirector(*decryption_filter);

  bool const kPumpAll = true;
  CryptoPP::StringSource(
      kCipherText,
      kPumpAll,
      transformator);

  return recovered_plain_text;
}

int main() {
  CryptoPP::AutoSeededRandomPool prng;
  CryptoPP::SecByteBlock key(CryptoPP::Blowfish::DEFAULT_KEYLENGTH);
  prng.GenerateBlock(key, key.size());

  byte iv[CryptoPP::Blowfish::BLOCKSIZE];
  prng.GenerateBlock(iv, sizeof(iv));

  // Creates templated mode objects of  block ciphers.

  // This works...
//  CryptoPP::EAX<CryptoPP::Blowfish>::Encryption encryption;
//  CryptoPP::EAX<CryptoPP::Blowfish>::Decryption decryption;

  // This does NOT work...
  CryptoPP::GCM<CryptoPP::Blowfish>::Encryption encryption;
  CryptoPP::GCM<CryptoPP::Blowfish>::Decryption decryption;

  std::string plain_text = "Block Mode Test";
  std::string cipher_text = encrypt(encryption, plain_text, key, iv);
  // terminate called after throwing an instance of 'CryptoPP::InvalidArgument'
  // what():  Blowfish/GCM: block size of underlying block cipher is not 16

  std::cout << "cipher text: " << std::hex << cipher_text << std::endl;
  std::cout << "recovered plain text: " << decrypt(decryption, cipher_text, key, iv) << std::endl;
}

A CryptoPP::InvalidArgumentexception occurs when you run the code above with the following text:

Blowfish/GCM: block size of underlying block cipher is not 16

But when you run the code instead with EAX block mode, an exception is not thrown. So my questions are:

• Does GCM work only with AES? Can GCM also be used with Blowfish or 3DES?
• , ?
• Crypto ++? BlockSize() 0, Blowfish ( 3DES) AES. , , .

Answer 1

GCM 128- (= 16 ) . 5.1.

Blowfish - 64- , "" . 3DES. ​​Crypto ++.

GCM Crypto ++ 128- . AES, Cast-256, Rijndael Cameilla, MARS, Serpent Twofish. Applied Crypto ++: Block Ciphers.

GCM . , Rijndael ( AES) 192- 256- (AES 128- ). GCM . SHACAL-2 256- .

Crypto ++ BlockSize() 0 ( ). , AES::BLOCKSIZE, Camellia::BLOCKSIZE Rijndael::BLOCKSIZE. .