(MFC) Encrypt File to PKCS7 .p7m

MFC 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.

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

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkCrypt2 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("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("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
    CkCert encryptCert;
    bool success = encryptCert.LoadFromFile("/Users/chilkat/testData/cer/acme.cer");
    if (success != true) {
        strOut.append(encryptCert.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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 char *inFile = "/Users/chilkat/testData/pdf/sample.pdf";
    const char *outFile = "/Users/chilkat/testData/p7m/sample.pdf.p7m";
    success = crypt.CkEncryptFile(inFile,outFile);
    if (success != true) {
        strOut.append(crypt.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // For demonstration purposes, a different instance of the object will be used
    // for decryption.
    CkCrypt2 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 char *pfxFilename = "/Users/chilkat/testData/pfx/acme.pfx";
    const char *pfxPassword = "secret";

    // Tell the component to look in the PFX file for certs and private keys.
    success = decrypt.AddPfxSourceFile(pfxFilename,pfxPassword);
    if (success != true) {
        strOut.append(decrypt.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

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

    // Decrypt the .p7m
    inFile = "/Users/chilkat/testData/p7m/sample.pdf.p7m";
    outFile = "/Users/chilkat/testData/pdf/recovered.pdf";
    success = decrypt.CkDecryptFile(inFile,outFile);
    if (success == false) {
        strOut.append(decrypt.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("Success!");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }