(MFC) RSA Encrypt and Decrypt Credit Card Numbers

MFC 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.)

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

    // 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 PKCS8 file:
    bool success = key.LoadPkcs8File("rsaPrivateKey.p8");
    if (success != true) {
        strOut.append(key.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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) {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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);
    strOut.append("Encrypted:");
    strOut.append("\r\n");
    strOut.append(encryptedStr);
    strOut.append("\r\n");

    // Now decrypt:
    CkRsa rsaDecryptor;

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

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

    strOut.append("Decrypted:");
    strOut.append("\r\n");
    strOut.append(decryptedStr);
    strOut.append("\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


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }