(C) Encrypt a file to a PKCS7 encrypted message using multiple certificates from different users

Demonstrates how to encrypt a file to a PKCS7 encrypted message using multiple certificates from different users. Any one of the users can decrypt using his/her own certificate + private key.

Note: When doing public key encryption, it is the public key that is used to encrypt. The private key is required for decryption.

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#include <C_CkCrypt2.h>
#include <C_CkCert.h>
#include <C_CkBinData.h>

void ChilkatSample(void)
    {
    HCkCrypt2 crypt;
    HCkCert cert1;
    BOOL success;
    HCkCert cert2;
    HCkCert cert3;
    HCkBinData fileData;

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

    crypt = CkCrypt2_Create();

    //  Tell the crypt object to use 3 certificates.
    //  Do this by calling AddEncryptCert for each certificate.

    //  Load a digital certificate.
    //  We don't need the private key for encryption.
    //  Only the public key is needed (which is included in a certificate).
    cert1 = CkCert_Create();
    success = CkCert_LoadFromFile(cert1,"qa_data/user1/cert_user1.pem");
    //  Assume success for the example, but make sure your application checks for success/failure...
    CkCrypt2_AddEncryptCert(crypt,cert1);

    cert2 = CkCert_Create();
    success = CkCert_LoadFromFile(cert2,"qa_data/user2/cert_user2.pem");
    CkCrypt2_AddEncryptCert(crypt,cert2);

    cert3 = CkCert_Create();
    success = CkCert_LoadFromFile(cert3,"qa_data/user3/cert_user3.pem");
    CkCrypt2_AddEncryptCert(crypt,cert3);

    //  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-128 for the
    //  bulk encryption.
    CkCrypt2_putCryptAlgorithm(crypt,"pki");
    CkCrypt2_putPkcs7CryptAlg(crypt,"aes");
    CkCrypt2_putKeyLength(crypt,128);
    CkCrypt2_putOaepHash(crypt,"sha256");
    CkCrypt2_putOaepPadding(crypt,TRUE);

    //  Load the file to be encrypted...
    fileData = CkBinData_Create();
    success = CkBinData_LoadFile(fileData,"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 = CkCrypt2_EncryptBd(crypt,fileData);
    if (success != TRUE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkCrypt2_Dispose(crypt);
        CkCert_Dispose(cert1);
        CkCert_Dispose(cert2);
        CkCert_Dispose(cert3);
        CkBinData_Dispose(fileData);
        return;
    }

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

    //  Now indicate that the PKCS7 output is to be returned in the base64 encoding.
    CkCrypt2_putEncodingMode(crypt,"base64");

    printf("OK.\n");


    CkCrypt2_Dispose(crypt);
    CkCert_Dispose(cert1);
    CkCert_Dispose(cert2);
    CkCert_Dispose(cert3);
    CkBinData_Dispose(fileData);

    }