Encrypt File to .p7m

C# example program to encrypt a file to produce a .p7m as output. A digital certificate (public-key) is used for encrypting.

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

//  Any string argument automatically begins the 30-day trial.
bool success;
success = crypt.UnlockComponent("30-day trial");
if (success != true) {
    MessageBox.Show("Crypt component unlock failed");
    return;
}

//  Use public-key encryption with a digital certificate:
crypt.CryptAlgorithm = "pki";

//  There are many ways to select and load a digital certificate.
//  Certs can be retrieved from the Windows registry-based
//  certificate stores, from database tables, files, etc.
//  This example will load a .cer file.
Chilkat.Cert cert = new Chilkat.Cert();

success = cert.LoadFromFile("myCert.cer");
if (success != true) {
    MessageBox.Show(cert.LastErrorText);
    return;
}

crypt.SetEncryptCert(cert);

//  The CkEncryptFile can encrypt files of any size.  The
//  encryption occurs in streaming mode, so it is not necessary
//  to hold the entire contents of the file in memory at once.
success = crypt.CkEncryptFile("dude.gif","dude.p7m");
if (success != true) {
    MessageBox.Show(crypt.LastErrorText);
    return;
}

//  To decrypt the file, you'll need the private key.
//  Also, the certificate should have already been installed
//  on the computer.  This is typically achieved by installing
//  from a .pfx file, or by importing from a certificate
//  authority's online web application.  If you are decrypting
//  from ASP, ASP.NET, or a Windows Service, you'll need to
//  import in a way that provides the calling process permission
//  to access and use the private key.  The procedure for
//  doing this is explained here:
//  http://blog.chilkatsoft.com/?p=149
// 
//  Also, there is no "SetDecryptCert" method.  The .p7m
//  contains information that allows the Chilkat component
//  to locate the certificate to be used for decryption.
//  The Chilkat Crypt component automatically searches
//  the Windows Current User certificate store and the
//  Local Machine certificate store.
success = crypt.CkDecryptFile("dude.p7m","dudeOut.gif");
if (success != true) {
    MessageBox.Show(crypt.LastErrorText);
    return;
}