(Unicode C++) Encrypt File to PKCS7 .p7m

Unicode C++ example to public-key encrypt a file creating a PKCS#7 .p7m file as output. Also demonstrates how to decrypt the .p7m to recover the original file.

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#include <CkCrypt2W.h>
#include <CkCertW.h>

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

    CkCrypt2W crypt;

    // Indicate the public-key encryption is to be used.
    // Do this by setting the encryption algorithm equal 
    // to "PKI" (an acroynm for public-key infrastructure).
    crypt.put_CryptAlgorithm(L"PKI");

    // Indicate the inner symmetric encryption algorithm to be used.
    // possible values are "aes", "des", "3des", and "rc2".
    // For this example, we'll use 256-bit AES encryption.
    crypt.put_Pkcs7CryptAlg(L"aes");
    crypt.put_KeyLength(256);

    // To encrypt, only a certificate w/ public key is needed.
    // (The certificate w/ private key is required for decryption.)

    // The LoadFromFile method can load virtually any certificate format:
    // 1. DER encoded binary X.509 (.CER)
    // 2. Base-64 encoded X.509 (.CER)
    // 3. Cryptographic Message Syntax Standard - PKCS #7 Certificates (.P7B)
    // 4. PEM format
    CkCertW encryptCert;
    bool success = encryptCert.LoadFromFile(L"/Users/chilkat/testData/cer/acme.cer");
    if (success != true) {
        wprintf(L"%s\n",encryptCert.lastErrorText());
        return;
    }

    // Tell the crypt object to use the certificate for encrypting:
    crypt.AddEncryptCert(encryptCert);

    // Encrypt a file, producing a .p7m as output.
    // The input file is unchanged, the output .p7m contains the encrypted
    // contents of the input file.
    const wchar_t *inFile = L"/Users/chilkat/testData/pdf/sample.pdf";
    const wchar_t *outFile = L"/Users/chilkat/testData/p7m/sample.pdf.p7m";
    success = crypt.CkEncryptFile(inFile,outFile);
    if (success != true) {
        wprintf(L"%s\n",crypt.lastErrorText());
        return;
    }

    // For demonstration purposes, a different instance of the object will be used
    // for decryption.
    CkCrypt2W decrypt;

    // To decrypt, the certificate w/ private key is required.  A PFX (also known
    // as PKCS#12) is a common secure container for certs and private keys.
    const wchar_t *pfxFilename = L"/Users/chilkat/testData/pfx/acme.pfx";
    const wchar_t *pfxPassword = L"secret";

    // Tell the component to look in the PFX file for certs and private keys.
    success = decrypt.AddPfxSourceFile(pfxFilename,pfxPassword);
    if (success != true) {
        wprintf(L"%s\n",decrypt.lastErrorText());
        return;
    }

    // Tell the decrypt object that PKI (public key encryption) is to be used
    // for decryptiong.
    decrypt.put_CryptAlgorithm(L"PKI");
    // There is no need to set the Pkcs7Alg or KeyLength because this information
    // is contained within the .p7m

    // Decrypt the .p7m
    inFile = L"/Users/chilkat/testData/p7m/sample.pdf.p7m";
    outFile = L"/Users/chilkat/testData/pdf/recovered.pdf";
    success = decrypt.CkDecryptFile(inFile,outFile);
    if (success == false) {
        wprintf(L"%s\n",decrypt.lastErrorText());
        return;
    }

    wprintf(L"Success!\n");
    }