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. C#

bool success = false;

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

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();

//  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).
Chilkat.Cert cert1 = new Chilkat.Cert();
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.CryptAlgorithm = "pki";
crypt.Pkcs7CryptAlg = "aes";
crypt.KeyLength = 256;
crypt.OaepHash = "sha256";
crypt.OaepPadding = true;

//  Load the file to be encrypted...
Chilkat.BinData fileData = new Chilkat.BinData();
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) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

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

Debug.WriteLine("OK.");