(C++) RSA Encrypt and Decrypt Credit Card Numbers

C++ sample code to RSA public-key encrypt and decrypt credit card numbers. The RSA key is loaded from an unencrypted PKCS8 file. Chilkat provides many ways of setting the key -- loading from both encrypted and unencrypted PEM, PKCS8, DER, PVK, etc. Keys may be loaded from files or in-memory representations. (The RSA component also provides the ability to generate RSA keys.)

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#include <CkRsa.h>
#include <CkPrivateKey.h>

void ChilkatSample(void)
    {
    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkRsa rsa;

    CkPrivateKey key;

    // Load an RSA private key from a file:
    bool success = key.LoadAnyFormatFile("rsaPrivateKey.key","");
    if (success != true) {
        std::cout << key.lastErrorText() << "\r\n";
        return;
    }

    // Get the key as XML:
    const char *keyXml = 0;
    keyXml = key.getXml();

    // We'll encrypt with the public key and decrypt with the private
    // key.  (It's also possible to do the reverse.)
    // Note: An RSA private key is composed of different parts internally: modulus, exponent, P, Q, etc.
    // An RSA public-key is a sub-set of the private key.
    // Therefore, when you have a private key, you really have
    // both public and private keys.
    success = rsa.ImportPublicKey(keyXml);
    if (success != true) {
        std::cout << rsa.lastErrorText() << "\r\n";
        return;
    }

    // Encrypt a VISA credit card number:
    // 1234-5678-0000-9999
    const char *ccNumber = "1234567800009999";

    bool usePrivateKey = false;
    rsa.put_EncodingMode("base64");
    const char *encryptedStr = rsa.encryptStringENC(ccNumber,usePrivateKey);
    std::cout << "Encrypted:" << "\r\n";
    std::cout << encryptedStr << "\r\n";

    // Now decrypt:
    CkRsa rsaDecryptor;

    rsaDecryptor.put_EncodingMode("base64");
    success = rsaDecryptor.ImportPrivateKey(keyXml);

    usePrivateKey = true;
    const char *decryptedStr = rsaDecryptor.decryptStringENC(encryptedStr,usePrivateKey);

    std::cout << "Decrypted:" << "\r\n";
    std::cout << decryptedStr << "\r\n";

    // Important: RSA encryption should only be used to encrypt small amounts of data.
    // It is typically used for encrypting symmetric encryption
    // keys such that a symmetric encryption algorithm, such as 
    // AES is then used to encrypt/decrypt bulk data
    }