(MFC) Encrypt with Chilkat, Decrypt with OpenSSL

Demonstrates how to RSA encrypt a string using Chilkat, and then shows the corresponding OpenSSL command to RSA decrypt. The OpenSSL command to decrypt is as follows:

openssl rsautl -decrypt -inkey VP_Private.pem -in rsa_encrypted.bin -out original.txt

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

See Also: Using MFC CString in Chilkat

#include <CkRsa.h>
#include <CkPublicKey.h>
#include <CkByteData.h>
#include <CkFileAccess.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkRsa rsa;

    // Note: RSA encryption uses the public key.  
    // RSA decryption uses the private key.
    // The reason is that the public key can be freely provided to anybody.  This allows anybody
    // to send an encrypted message to the private key owner, and only the private key owner 
    // can decrypt.
    CkPublicKey key;

    // Load an RSA public key from a PEM file:
    bool success = key.LoadFromFile("qa_data/pem/VP_Public.pem");
    if (success != true) {
        strOut.append(key.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Load the public key into the RSA object.
    success = rsa.ImportPublicKeyObj(key);
    if (success != true) {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    const char *strToEncrypt = "00000000;XYZ2-3BHQ-ABCD-MMVV;6MY1-GHJK-9LRR;0";

    // The LittleEndian property is false by default, but it is set here
    // anyway to show that LittleEndian byte ordering is required for OpenSSL compatibility.
    rsa.put_LittleEndian(false);

    bool usePrivateKey = false;
    CkByteData encryptedBytes;
    success = rsa.EncryptString(strToEncrypt,usePrivateKey,encryptedBytes);
    if (rsa.get_LastMethodSuccess() != true) {
        strOut.append(rsa.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // The OpenSSL command to decrypt would be this:
    // openssl rsautl -decrypt -inkey VP_Private.pem -in rsa_encrypted.bin -out original.txt

    CkFileAccess fac;
    success = fac.WriteEntireFile("qa_output/rsa_encrypted.bin",encryptedBytes);
    if (success != true) {
        strOut.append(fac.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("RSA Encryption Succeeded.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }