ECIES Public Key Serialization

Question

I am writing a client / server program and want to send the ECIES public key. To do this, I have to serialize the public key into a file, read the file into a byte array, send this array of bytes. On the other hand: get an array of bytes, write it to a file, deserialize the public key from the file. So, I wrote several test projects to try to do this separately from an excellent system, and (when this whole module works successfully) just paste it into my project. Code for this project:

class EncoderRSA
{
    public:
        EncoderRSA();
        void keyGeneration();
        std::string encrypt(std::string plainText);
        std::string decrypt(std::string cypher);
        void setRsaPublicKey(char *publicKeyInCharArray);
        char *getRsaPublicKey();
    private:
        AutoSeededRandomPool prng;  // Pseudo Random Number Generator
        ECIES<ECP>::Decryptor rsaDecryptor;
        ECIES<ECP>::Encryptor rsaEncryptor;
};

And, strictly speaking, simple (for the task) methods:

char *EncoderRSA::getRsaPublicKey() {
    std::string file = "publicKey.txt";

    //Save public key in file
    FileSink sink(file.c_str());
    this->rsaEncryptor.GetPublicKey().Save(sink);

    //Read file with public key into the buffer
    std::ifstream infile (file.c_str(),std::ifstream::binary);

    if (!infile.is_open()) {
        std::cout << "Can't open file to write" << std::endl;
        exit(1);
    }

    // get size of file
    infile.seekg (0,infile.end);
    long size = infile.tellg();
    infile.seekg (0);

    // allocate memory for file content
    char* buffer = new char[size];
    infile.read (buffer,size);
    infile.close();

    return buffer;
}

void EncoderRSA::setRsaPublicKey(char *publicKeyInCharArray) {
    std::string file = "publicKey.txt";

    int size = strlen(publicKeyInCharArray);

    //Write received public key in file
    std::ofstream outfile (file.c_str(),std::ofstream::binary);

    if (!outfile.is_open()) {
        std::cout << "Can't open file to write" << std::endl;
        exit(1);
    }

    outfile.write (publicKeyInCharArray,size);
    outfile.close();

    // release dynamically-allocated memory
    delete[] publicKeyInCharArray;

    //Load public key from file
    FileSource source(file.c_str(), true);
    this->rsaEncryptor.AccessPublicKey().Load(source);
}

Code main.cpp:

int main() {
    char *buffer = keysEncoder.getRsaPublicKey();
    cout << "buffer: " << buffer << endl;
    //...
    //send buffer
    //receive buffer from other side
    //..
    keysEncoder.setRsaPublicKey(buffer);

    string decoded = keysEncoder.decrypt(cypher);
    cout << "decoded: " << decoded << endl;

    return 0;
}

But he crashed with an error:

terminate called after throwing an instance of 'CryptoPP::BERDecoderErr'
wait(): BER decode error
Aborted (core dumped)

Process returned 134 (0x86)    execution time: 2.891

Why?

Answer 1

RSA, , ECIES. .

---

'CryptoPP:: BERDecoderErr'

, try/catch:

try
{
    ...
}
catch(const BERDecoderErr& ex)
{
    cerr << ex.what() << endl;
}

---

char *Encoder::getPublicKey() {
    ...
    char* buffer = ...
    return buffer;
}

ASN.1/DER, , NULL, , C-.

, , std::string, NULL:

// get size of file
infile.seekg (0,infile.end);
long size = infile.tellg();
infile.seekg (0);

// allocate memory for file content
string buffer(size, '0');
infile.read (&buffer[0], size);
infile.close();

return buffer;

---

ASCII ++ std::string:

std::ifstream infile (file.c_str(), std::ifstream::binary);
std::string buffer((std::istreambuf_iterator<char>(infile)),
                    std::istreambuf_iterator<char>());

---

, NULL :

string Encoder::getPublicKey() {
    string encodedKey;
    HexEncoder sink(new StringSink(encodedKey));
    Encryptor.GetPublicKey().Save(sink);
    return encodedKey;
}

void Encoder::setPublicKey(const string& encodedKey) {
    StringSource source(encodedKey, new HexDecoder());
    Encryptor.AccessPublicKey().Load(source);
}

StringSource StringSink, . , FileSource FileSink.