如何：为多个收件人封装邮件
此示例使用 System.Security.Cryptography.Pkcs 创建 CMS/PKCS #7 封装邮件。该邮件针对多个收件人进行加密。可使用收件人的私钥为每个收件人解密该邮件。此示例使用 EnvelopedCms 对象，从而可以针对一个或多个收件人对邮件进行加密，或“封装”**。
示例
此示例使用下列类：
EnvelopedCms
要在一台计算机上运行，以下示例要求“通讯簿”和“我的证书”存储中均包含两个使用者名称分别为“Recipient1”和“Recipient2”的公钥证书。此示例还要求该计算机上存储有关联的私钥。示例代码先充当邮件发件人，然后再充当邮件收件人。每个角色中使用相同的公钥凭据。同样，该示例要求两个存储中均包含公钥证书。作为发件人，该示例在“通讯簿”证书存储中搜索收件人的证书并用来加密邮件。作为收件人，该示例在“我的证书”存储中搜索该证书，并使用关联的私钥解密邮件。
.gif) 注意: |
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这只是一个说明性的示例。生产环境可能会使用不同的模型，邮件的发件人和收件人在不同的进程中使用唯一的公钥凭据执行操作。 |
使用 Makecert.exe 实用程序设置此示例，可以通过多种方法实现。Certificate Creation Tool (Makecert.exe) 是用于测试证书的一种很方便的实用程序。在生产环境中，证书由证书颁发机构生成。
下列 Makecert 命令生成所需的公钥证书和私钥。
Makecert -n "CN=Recipient1" -ss My
Makecert -n "CN=Recipient2" -ss My
这些命令将相应的公钥证书放入“我的证书”存储。此时，需要导出公钥证书，然后将其导入每个收件人的“通讯簿”证书存储，请遵照如何：导出和导入公钥证书中的步骤执行。
// 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();
}
}
}
请参见
任务
如何：由一个签名者为邮件签名
如何：由多个签名者为邮件签名
如何：对邮件进行副署
如何：为一个收件人封装邮件
概念
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