(C++) Encrypt a File to a PKCS7 (CMS) Message

Shows how to encrypt a file into a PKCS7 encrypted message using the recipient's certificate. Public-key encryption requires no private key. However, the recipient's private key is necessary for decryption.

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#include <CkCrypt2.h>
#include <CkCert.h>
#include <CkBinData.h>

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

    CkCrypt2 crypt;

    // Load the recipient's digital certificate. 
    // We don't need the private key for encryption.
    // Only the public key is needed (which is included in a certificate).
    CkCert cert1;
    bool success = cert1.LoadFromFile("qa_data/user1/cert_user1.pem");
    // Assume success for the example, but make sure your application checks for success/failure...
    crypt.SetEncryptCert(cert1);

    // Indicate that we want PKI encryption (i.e. public-key infrastructure)
    // to produce a CMS message (Cryptographic Message Syntax/PKCS7),
    // that is be created with RSAES-OAEP padding, SHA256, and AES-256 for the
    // bulk encryption.
    crypt.put_CryptAlgorithm("pki");
    crypt.put_Pkcs7CryptAlg("aes");
    crypt.put_KeyLength(256);
    crypt.put_OaepHash("sha256");
    crypt.put_OaepPadding(true);

    // Load the file to be encrypted...
    CkBinData fileData;
    success = fileData.LoadFile("qa_data/jpg/penguins.jpg");
    // Your app should check for success/failure..

    // Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
    success = crypt.EncryptBd(fileData);
    if (success != true) {
        std::cout << crypt.lastErrorText() << "\r\n";
        return;
    }

    // Save the PKCS7 encrypted message to a file..
    success = fileData.WriteFile("qa_output/pkcs7_encrypted.p7");

    std::cout << "OK." << "\r\n";
    }