Question

Resolved (look for my answer). I need help encrypting a password with RSA in C++. I’m working for Blackberry10 in C++ and I’ve been looking for a RSA tutorial or something that walk me through the encrypting process but sadly I haven’t found anything consistant.

I’ve been told that the process consist basicaly in three steps:

1)Generate the RSA public key with the module and exponent.
2)Encrypt the text with the public key.
3)Encrypt the text again in base640.

If you are wondering why I need to follow this three steps is because I’m working in a banking app, and those are their requirements.

I’ve been searching all over and I haven’t found even how to make the first step, generate the public key with the module and the exponent (I already have both).

Any help will be appreciated.

Thanks.

---

Is not that I’m building the whole app by myself. We are a team and I need to encrypt just the client password with RSA and send it to the next step of the process. I do have experiencie working with Blackberry and RSA but in Java, where the process is a little bit easier, e.g: In java the first step once you got the module and public exponent is create the RSA Public Key Object through a very simple syntaxis: RSAPublicKey publicKey = new RSAPublicKey(new RSACryptoSystem(2048),ebytes, mbytes);. In this part is where I’m little bit lost because I haven’t found the proper BB10 documentation. I’m sorry if I created the illusion that I’m creating a whole encryption API by myself. BB10 has this security API based in hursa.h (https://developer.blackberry.com/native/beta/reference/com.qnx.doc.crypto/topic/about_rsa_raw.html) I’m trying to implement it, but I haven’t been successful. @owlstead @dajames @bta

Answer 1

Resolved. After doing some research and getting to know better with BB10 coding and RSA, I finally came out with the solution to successfuly encrypt a plain text with RSA and Base64 in C/C++ for BB10 or any other platform. Please take in consideration that I have the modulus and the public exponent of the rsa object from the services that I’m working with.

The code:

    QByteArray answer;

    RSA* rsa = RSA_new();

    BIGNUM *modulus = BN_new();
    BIGNUM *exponent = BN_new();
    const char *modulusString = rsaObj->getM(); //My Modulus
    const char *exponentString = rsaObj->getE(); //My exponent

    BN_hex2bn(&modulus, modulusString);
    BN_hex2bn(&exponent, exponentString);

    rsa->n = BN_new();
    BN_copy(rsa->n, modulus);
    rsa->e = BN_new();
    BN_copy(rsa->e, exponent);

    int maxSize = RSA_size(rsa);
    qDebug() << "maxSize:" << maxSize;

    const char *inn = "1234";
    unsigned char *encrypted = (unsigned char*) malloc(maxSize);
    int bufferSize = RSA_public_encrypt(strlen(inn), (unsigned char *) inn,
            encrypted, rsa, RSA_PKCS1_PADDING);

    if (bufferSize == -1) {
        RSA_free(rsa);
        qDebug() << "Error";
    }

    QByteArray enc = QByteArray::fromRawData((const char*) encrypted, 256);
    answer = enc.toBase64();

    return answer;

Thanks and I expect this helps to the new BB10 developers