(C#) Send aes-gcm authEnvelopedData Encrypted Email

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Note: This example requires Chilkat v10.0.0 or later

Demonstrates how to send encrypted email using 128-bit AES in GCM mode.

"AES-GCM" (Advanced Encryption Standard - Galois/Counter Mode) is a cryptographic algorithm that provides both encryption and integrity protection (authentication). When used in the context of email security with "authEnvelopedData", it often refers to a method of securely sending encrypted and authenticated email content.

Here’s a brief breakdown:

• AES-GCM: Combines symmetric encryption (AES) with authentication, ensuring both the confidentiality and integrity of the message. It generates an authentication tag to detect any unauthorized changes.
• authEnvelopedData: Refers to a type of structure used in secure email protocols (like S/MIME) to package encrypted content. It contains the encrypted data and associated encrypted session keys.
• Email Security: When applied to emails, AES-GCM ensures the email content is encrypted (confidential) and also tamper-resistant (authenticated), with the encryption keys typically shared securely using asymmetric encryption (e.g., public key infrastructure, or PKI).

In short, AES-GCM with "authEnvelopedData" provides a way to encrypt and authenticate emails, making them confidential and resistant to tampering.

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

// The mailman object is used for sending and receiving email.
Chilkat.MailMan mailman = new Chilkat.MailMan();

mailman.SmtpHost = "smtp.example.com";

mailman.SmtpUsername = "my_smtp_login";
mailman.SmtpPassword = "my_smtp_password";

// The typical SMTP ports are 465 for implicit SSL/TLS or 587 for explicit SSL/TLS
mailman.SmtpPort = 465;
mailman.SmtpSsl = true;

// Use the recipient's certificate for encryption.
Chilkat.Cert cert = new Chilkat.Cert();
bool success = cert.LoadFromFile("c:/someDir/recipient_cert.cer");
if (success != true) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

Chilkat.Email email = new Chilkat.Email();

email.Subject = "This email is encrypted";
email.Body = "This is AES-GCM encrypted mail";
email.From = "Mary <mary@example1.com>";
success = email.AddTo("Joe","joe@example.com");

// Specify that AES-GCM w/ authEnvelopedData is to be used. 
// Also specify other params..
email.Pkcs7CryptAlg = "aes-gcm";
email.Pkcs7KeyLength = 128;
email.OaepPadding = true;
email.OaepHash = "sha256";
email.OaepMgfHash = "sha256";

// Indicate the email is to be sent encrypted.
email.SendEncrypted = true;

// Specify the certificate to be used for encryption.
success = email.SetEncryptCert(cert);

success = mailman.SendEmail(email);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
}
else {
    Debug.WriteLine("Mail Sent!");
}