(MFC) RSA Encrypt and Decrypt Strings

MFC sample code to RSA public-key encrypt and decrypt strings using public and private keys.

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

See Also: Using MFC CString in Chilkat

#include <CkRsa.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;

    // This example also generates the public and private
    // keys to be used in the RSA encryption.
    // Normally, you would generate a key pair once,
    // and distribute the public key to your partner.
    // Anything encrypted with the public key can be
    // decrypted with the private key.  The reverse is 
    // also true: anything encrypted using the private
    // key can be decrypted using the public key.

    // Generate a 1024-bit key.  Chilkat RSA supports
    // key sizes ranging from 512 bits to 4096 bits.
    bool success = rsa.GenerateKey(1024);
    if (success != true) {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Keys are exported in XML format:
    const char *publicKey = rsa.exportPublicKey();
    const char *privateKey = rsa.exportPrivateKey();

    const char *plainText = "Encrypting and decrypting should be easy!";

    // Start with a new RSA object to demonstrate that all we
    // need are the keys previously exported:
    CkRsa rsaEncryptor;

    // Encrypted output is always binary.  In this case, we want
    // to encode the encrypted bytes in a printable string.
    // Our choices are "hex", "base64", "url", "quoted-printable".
    rsaEncryptor.put_EncodingMode("hex");

    // We'll encrypt with the public key and decrypt with the private
    // key.  It's also possible to do the reverse.
    success = rsaEncryptor.ImportPublicKey(publicKey);

    bool usePrivateKey = false;
    const char *encryptedStr = rsaEncryptor.encryptStringENC(plainText,usePrivateKey);
    strOut.append(encryptedStr);
    strOut.append("\r\n");

    // Now decrypt:
    CkRsa rsaDecryptor;

    rsaDecryptor.put_EncodingMode("hex");
    success = rsaDecryptor.ImportPrivateKey(privateKey);

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

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


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }