如何：为一个收件人封装邮件
此示例使用 System.Security.Cryptography.Pkcs 创建 CMS/PKCS #7 封装邮件。该邮件针对单个收件人进行加密。可使用该收件人的私钥解密该邮件。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：
要在一台计算机上运行，以下示例要求“通讯簿”和“我的证书”存储中均包含使用者名称为“Recipient1”的公钥证书。此示例还要求该计算机上存储有关联的私钥。此示例通过在每个角色中使用相同的公钥凭据，先充当邮件发件人，然后再充当邮件收件人。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使用该证书来加密邮件。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) 是用于生成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
此命令将相应的公钥证书放入“我的证书”存储并生成私钥。此时，需要将公钥证书的副本放入“通讯簿”证书存储。要实现此目的，导出公钥证书，然后将其导入“通讯簿”证书存储，请遵循如何：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 EnvelopAMessageForOneRecipient
{
class EnvelopedCmsSingleRecipient
{
const String recipientName = "Recipient1";
static void Main(string[] args)
{
Console.WriteLine("System.Security.Cryptography.Pkcs " +
"Sample: Single-recipient encrypted and decrypted message");
// Original message.
const String msg = "Here is your personal identification number:";
Console.WriteLine("\nOriginal message (len {0}): {1} ",
msg.Length, msg);
// Convert message to an 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 recipient's certificate is necessary to encrypt
// the message for that recipient.
X509Certificate2 recipientCert = GetRecipientCert();
Console.WriteLine("\n\n----------------------");
Console.WriteLine(" SENDER SIDE ");
Console.WriteLine("----------------------\n");
byte[] encodedEnvelopedCms = EncryptMsg(msgBytes,
recipientCert);
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");
Byte[] decryptedMsg = DecryptMsg(encodedEnvelopedCms);
// Convert Unicode bytes to the original message string.
Console.WriteLine("\nDecrypted Message: {0}",
unicode.GetString(decryptedMsg));
}
// Open the AddressBook (also known as Other in
// Internet Explorer) certificate store and search for
// a recipient certificate with which to encrypt the
// message. The certificate must have a subject name
// of "Recipient1".
static public X509Certificate2 GetRecipientCert()
{
// 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 certificate.
// For purposes of this sample, do not validate the
// certificate. Note that in a production environment,
// validating the certificate will probably be necessary.
X509Certificate2Collection certColl = storeAddressBook.
Certificates.Find(X509FindType.FindBySubjectName,
recipientName, false);
Console.WriteLine(
"Found {0} certificates in the {1} store with name {2}",
certColl.Count, storeAddressBook.Name, recipientName);
// 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.");
}
storeAddressBook.Close();
return certColl[0];
}
// Encrypt the message with the public key of
// the recipient. This is done by enveloping the message by
// using an EnvelopedCms object.
static public byte[] EncryptMsg(
Byte[] msg,
X509Certificate2 recipientCert)
{
// Place the message in a ContentInfo object.
// This is required to build an EnvelopedCms object.
ContentInfo contentInfo = new ContentInfo(msg);
// Instantiate an 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 CmsRecipient object that
// represents information about the recipient
// to encrypt the message for.
CmsRecipient recip1 = new CmsRecipient(
SubjectIdentifierType.IssuerAndSerialNumber,
recipientCert);
Console.Write(
"Encrypting data for a single recipient of " +
"subject name {0} ... ",
recip1.Certificate.SubjectName.Name);
// Encrypt the message for the recipient.
envelopedCms.Encrypt(recip1);
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.
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 1 for this example.
DisplayEnvelopedCms(envelopedCms, false);
// Decrypt the message for the single recipient.
Console.Write("Decrypting Data ... ");
envelopedCms.Decrypt(envelopedCms.RecipientInfos[0]);
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 CMS/PKCS #7 Message " +
"Information:");
Console.WriteLine(
"\tThe number of recipients for the Enveloped CMS/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 CMS/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：为多个收件人封装邮件
概念
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