HOW TO：封套多位收件者的訊息
此範例會使用 System.Security.Cryptography.Pkcs 建立 CMS/PKCS #7 封套訊息。此訊息會為多位收件者加密。接著，系統會使用每一位收件者的私密金鑰將訊息解密。範例中使用了 EnvelopedCms 物件，它可以讓訊息為一或多個收件者加密 (或稱*「封套」*)。
範例
本範例使用下列類別：
EnvelopedCms
若要在單一電腦上執行，下列範例的「通訊錄」憑證存放區和「我的」憑證存放區中都必須具有主體名稱為 "Recipient1" 和 "Recipient2" 的公開金鑰憑證。該電腦上也必須存放關聯的私密金鑰。此範例程式碼先扮演訊息傳送者，然後扮演訊息收件者。兩個角色都使用相同的公開金鑰認證。因此這個範例要求兩個存放區中都必須具有公開金鑰憑證。做為傳送者時，此範例會在「通訊錄」憑證存放區中搜尋收件者的憑證，並使用該憑證來加密訊息。做為收件者時，它會在「我的」憑證存放區中搜尋憑證，並使用關聯的私密金鑰將訊息解密。
.gif) 注意： |
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此範例僅用於示範。實際執行環境中可能使用不同的模型，其中訊息的傳送者和收件者會使用其唯一公開金鑰認證，在不同的處理序中執行。 |
使用 Makecert.exe 公用程式設定此範例，這是完成此工作的方法之一。Certificate Creation Tool (Makecert.exe) 是測試憑證的方便公用程式。在實際執行環境中，憑證是由憑證授權單位所產生。
下面的 Makecert 命令會產生必要的公開金鑰憑證和私密金鑰。
Makecert -n "CN=Recipient1" -ss My
Makecert -n "CN=Recipient2" -ss My
這些命令會將適當的公開金鑰憑證置於「我的」憑證存放區內。此時，您必須匯出公開金鑰憑證，然後再依照HOW TO：匯出和匯入公開金鑰憑證中的程序，為每一位收件者將其匯入「通訊錄」憑證存放區。
// Copyright (c) Microsoft Corporation. All rights reserved.
#region Using directives
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.Pkcs;
using System.Security.Cryptography.X509Certificates;
using System.Text;
#endregion
namespace EnvelopAMessageForMultipleRecipients
{
class EnvelopedCmsMultipleRecipients
{
const String recipientName1 = "Recipient1";
const String recipientName2 = "Recipient2";
static void Main(string[] args)
{
Console.WriteLine("System.Security.Cryptography.Pkcs " +
"Sample: Multiple-recipient " +
"encrypted and decrypted message");
// Original message.
const String msg = "To all department heads: The following " +
"organizational changes will be announced next week:";
Console.WriteLine("\nOriginal message (len {0}): {1} ",
msg.Length, msg);
// Convert message to array of Unicode bytes for signing.
UnicodeEncoding unicode = new UnicodeEncoding();
byte[] msgBytes = unicode.GetBytes(msg);
Console.WriteLine("\n\n------------------------------");
Console.WriteLine(" SETUP OF CREDENTIALS ");
Console.WriteLine("------------------------------\n");
// The recipients' certificates are necessary to encrypt
// the message for those recipients.
X509Certificate2Collection recipientCerts = GetRecipientCerts();
Console.WriteLine("\n\n----------------------");
Console.WriteLine(" SENDER SIDE ");
Console.WriteLine("----------------------\n");
byte[] encodedEnvelopedCms = EncryptMsg(msgBytes,
recipientCerts);
Console.Write("\nMessage after encryption (len {0}): ",
encodedEnvelopedCms.Length);
foreach (byte b in encodedEnvelopedCms)
{
Console.Write("{0:x}", b);
}
Console.WriteLine();
Console.WriteLine("\n\n------------------------");
Console.WriteLine(" RECIPIENT SIDE ");
Console.WriteLine("------------------------\n");
// Decrypts the message for one of the recipients.
// Return the decrypted message to display it.
Byte[] decryptedMsg = DecryptMsg(encodedEnvelopedCms);
// Convert Unicode bytes to the original message string.
Console.WriteLine("\nDecrypted Message: {0}",
unicode.GetString(decryptedMsg));
}
// Open the AddressBook (called Other in Internet Explorer)
// certificate store and search for recipient
// certificates with which to encrypt the message. It must
// include two certificates: one with the subject name
// "Recipient1", and one with the subject name "Recipient2".
static public X509Certificate2Collection GetRecipientCerts()
{
// Open the AddressBook local user X509 certificate store.
X509Store storeAddressBook = new X509Store(StoreName.
AddressBook, StoreLocation.CurrentUser);
storeAddressBook.Open(OpenFlags.ReadOnly);
// Display certificates to help troubleshoot the
// example's setup.
Console.WriteLine(
"Found certs with the following subject names in the " +
"{0} store:", storeAddressBook.Name);
foreach (X509Certificate2 cert in storeAddressBook.Certificates)
{
Console.WriteLine("\t{0}", cert.SubjectName.Name);
}
// Get recipient certificates.
// For purposes of this sample, do not validate the
// certificates. Note that in a production environment,
// validating the certificates will probably be necessary.
// Get first recipient certificate.
X509Certificate2Collection certColl = storeAddressBook.
Certificates.Find(X509FindType.FindBySubjectName,
recipientName1, false);
Console.WriteLine(
"Found {0} certificates in the {1} store with name {2}",
certColl.Count, storeAddressBook.Name, recipientName1);
X509Certificate2Collection recipientCerts =
new X509Certificate2Collection();
// Check to see if the certificate suggested by the example
// requirements is not present.
if (certColl.Count == 0)
{
Console.WriteLine(
"A suggested certificate to use for this example " +
"is not in the certificate store. Select " +
"an alternate certificate to use for " +
"signing the message.");
}
recipientCerts.Add(certColl[0]);
// Get second recipient certificate.
certColl = storeAddressBook.
Certificates.Find(X509FindType.FindBySubjectName,
recipientName2, false);
Console.WriteLine(
"Found {0} certificates in the {1} store with name {2}",
certColl.Count, storeAddressBook.Name, recipientName2);
// Check to see if the certificate suggested by the example
// requirements is not present.
if (certColl.Count == 0)
{
Console.WriteLine(
"A suggested certificate to use for this example " +
"is not in the certificate store. Select " +
"an alternate certificate to use for " +
"signing the message.");
}
recipientCerts.Add(certColl[0]);
storeAddressBook.Close();
return recipientCerts;
}
// Encrypt the message for each recipient by using the public
// key of that recipient. This is done by
// enveloping the message by using an EnvelopedCms object.
static public byte[] EncryptMsg(
Byte[] msg,
X509Certificate2Collection recipientCerts)
{
// Place message in a ContentInfo object.
// This is required to build an EnvelopedCms object.
ContentInfo contentInfo = new ContentInfo(msg);
// Instantiate EnvelopedCms object with the ContentInfo
// above.
// Has default SubjectIdentifierType IssuerAndSerialNumber.
// Has default ContentEncryptionAlgorithm property value
// RSA_DES_EDE3_CBC.
EnvelopedCms envelopedCms = new EnvelopedCms(contentInfo);
// Formulate a CmsRecipientCollection object that
// represents information about the set of recipients
// to encrypt the message for.
CmsRecipientCollection recips =
new CmsRecipientCollection(
SubjectIdentifierType.IssuerAndSerialNumber,
recipientCerts);
Console.WriteLine("\nEncrypting data for multiple " +
"recipients with subject names: ");
foreach (CmsRecipient recip in recips)
{
Console.WriteLine("\t" +
recip.Certificate.SubjectName.Name);
}
// Encrypt the message for the collection of recipients.
envelopedCms.Encrypt(recips);
Console.WriteLine("Done.");
// The encoded EnvelopedCms message contains the message
// ciphertext and the information about each recipient
// that the message was enveloped for.
return envelopedCms.Encode();
}
// Decrypt the encoded EnvelopedCms message for one of the
// recipients.
static public Byte[] DecryptMsg(byte[] encodedEnvelopedCms)
{
// Prepare object in which to decode and decrypt.
EnvelopedCms envelopedCms = new EnvelopedCms();
// Decode the message.
envelopedCms.Decode(encodedEnvelopedCms);
// Display the number of recipients the message is
// enveloped for; it should be 2 for this example.
DisplayEnvelopedCms(envelopedCms, false);
// Decrypt the message.
// The message is decrypted for the recipient that
// you find the first matching private key for.
// A line similar to the following, however,
// decrypts the message for a specified recipient. In
// in this case, the first recipient.
// envelopedCms.Decrypt(envelopedCms.RecipientInfos[0]);
Console.Write("Decrypting Data for one recipient ... ");
envelopedCms.Decrypt();
Console.WriteLine("Done.");
// The decrypted message occupies the ContentInfo property
// after the Decrypt method is invoked.
return envelopedCms.ContentInfo.Content;
}
// Display the ContentInfo property of an EnvelopedCms object.
static private void DisplayEnvelopedCmsContent(String desc,
EnvelopedCms envelopedCms)
{
Console.WriteLine(desc + " (length {0}): ",
envelopedCms.ContentInfo.Content.Length);
foreach (byte b in envelopedCms.ContentInfo.Content)
{
Console.Write(b.ToString() + " ");
}
Console.WriteLine();
}
// Display some properties of an EnvelopedCms object.
static private void DisplayEnvelopedCms(EnvelopedCms e,
Boolean displayContent)
{
Console.WriteLine("\nEnveloped PKCS #7 Message Information:");
Console.WriteLine(
"\tThe number of recipients for the Enveloped PKCS #7 " +
"is: {0}", e.RecipientInfos.Count);
for (int i = 0; i < e.RecipientInfos.Count; i++)
{
Console.WriteLine(
"\tRecipient #{0} has type {1}.",
i + 1,
e.RecipientInfos[i].RecipientIdentifier.Type);
}
if (displayContent)
{
DisplayEnvelopedCmsContent("Enveloped PKCS #7 Content", e);
}
Console.WriteLine();
}
}
}
請參閱
工作
HOW TO：由一位簽署者簽署訊息
HOW TO：由多位簽署者簽署一個訊息
HOW TO：副署訊息
HOW TO：封套單一收件者的訊息
概念
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