Decrypt P7M using PFX to get MIME

Demonstrates how to decrypt a .p7m (PKCS7) binary file using a certificate and private key from a PFX file. The result of the decryption (in this case) is MIME text that may be loaded into a Chilkat MIME object.

Note: Any type of file or data may be encrypted to produce a .p7m (PKCS7) encrypted file. This example was prompted by a customer needing to decrypt a MIME message. The final step of loading the decrypted text into a MIME object would be skipped if decrypting something other than MIME..

Download: Chilkat .NET Assemblies

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.LastErrorText);
    return;
}

//  Read the P7M file into memory.
byte[] p7mData = null;
p7mData = crypt.ReadFile("encrypted.p7m");

//  Setup the crypt object:

//  Indicate that public-key decryption is to be used.
crypt.CryptAlgorithm = "pki";

//  Add a PFX file to allow the crypt object to find
//  the certificate and private key needed for decryption
string pfxFilePath;
pfxFilePath = "myPfx.pfx";
string pfxPassword;
pfxPassword = "secret";
success = crypt.AddPfxSourceFile(pfxFilePath,pfxPassword);
if (success != true) {
    MessageBox.Show(crypt.LastErrorText);
    return;
}

//  Assuming the decrypted data will be text, decrypt to
//  a string.
string mimeText;
mimeText = crypt.DecryptString(p7mData);
if (mimeText == null ) {
    MessageBox.Show(crypt.LastErrorText);
    return;
}

//  Note: Chilkat Crypt and Chilkat MIME are separate products.
//  To use both objects, one would license the "Chilkat Bundle",
//  which provides licenses to all existing Chilkat products.
//  This is less expensive than licensing each of the two products separately.

Chilkat.Mime mime = new Chilkat.Mime();

success = mime.UnlockComponent("Anyting for 30-day trial");
if (success != true) {
    MessageBox.Show(mime.LastErrorText);
    return;
}

//  Load the MIME text into the MIME object.
success = mime.LoadMime(mimeText);
if (success != true) {
    MessageBox.Show(mime.LastErrorText);
    return;
}

//  Save the MIME to a file:
success = mime.SaveMime("outMime.txt");
if (success != true) {
    MessageBox.Show(mime.LastErrorText);
    return;
}

//  Success!  Output the MIME text:
textBox1.Text += mime.GetMime() + "\r\n";