How to: Sign a Message by Multiple Signers
This example creates a CMS/PKCS #7 signed message by using System.Security.Cryptography.Pkcs. The message is signed by multiple signers. The signatures on that message are then verified.
Example
This example uses the following classes:
The following example begins by using a previously generated encoded SignedCms message (signed by a signer with the subject name "MessageSigner1"), and then signs it a second time by a signer with the subject name "MessageSigner2". This example requires that a public key certificate with the subject name "MessageSigner2" be contained in the My certificate store, and that is has an associated private key.
.gif) Note |
|---|
This example is only for illustrative purposes. Production environments might use a different model in which the sender and the recipient of the message execute in different processes with their unique public key credentials. |
Set up this example by using the Makecert.exe utility, one of several ways to do so. Certificate Creation Tool (Makecert.exe) is a convenient utility for generating test certificates. In a production environment, certificates are generated by a certification authority.
The following Makecert command generates the required public key certificates and private keys.
Makecert -n "CN=MessageSigner2" -ss My
// Copyright (c) Microsoft Corporation. All rights reserved.
#region Using directives
using System;
using System.Security.Cryptography.Pkcs;
using System.Security.Cryptography.X509Certificates;
using System.Text;
#endregion
namespace SigningAMessageByMultipleSigners
{
class SignedCmsMultipleSigners
{
// Subject name of the second signer of the message.
const String signerName = "MessageSigner2";
static void Main(string[] args)
{
// An encoded SignedCms message that was generated
// previously. It is the message "The Board of Directors
// hereby adopts the resolution." signed by one signer
// with the subject name "MessageSigner1". This example
// adds a second signature to this encoded
// SignedCms message.
Byte[] signedMessage = {
0x30, 0x82, 0x03, 0x34, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
0xf7, 0x0d, 0x01, 0x07, 0x02, 0xa0, 0x82, 0x03, 0x25, 0x30,
0x82, 0x03, 0x21, 0x02, 0x01, 0x01, 0x31, 0x0b, 0x30, 0x09,
0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x30,
0x77, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01,
0x07, 0x01, 0xa0, 0x6a, 0x04, 0x68, 0x54, 0x00, 0x68, 0x00,
0x65, 0x00, 0x20, 0x00, 0x42, 0x00, 0x6f, 0x00, 0x61, 0x00,
0x72, 0x00, 0x64, 0x00, 0x20, 0x00, 0x6f, 0x00, 0x66, 0x00,
0x20, 0x00, 0x44, 0x00, 0x69, 0x00, 0x72, 0x00, 0x65, 0x00,
0x63, 0x00, 0x74, 0x00, 0x6f, 0x00, 0x72, 0x00, 0x73, 0x00,
0x20, 0x00, 0x68, 0x00, 0x65, 0x00, 0x72, 0x00, 0x65, 0x00,
0x62, 0x00, 0x79, 0x00, 0x20, 0x00, 0x61, 0x00, 0x64, 0x00,
0x6f, 0x00, 0x70, 0x00, 0x74, 0x00, 0x73, 0x00, 0x20, 0x00,
0x74, 0x00, 0x68, 0x00, 0x65, 0x00, 0x20, 0x00, 0x72, 0x00,
0x65, 0x00, 0x73, 0x00, 0x6f, 0x00, 0x6c, 0x00, 0x75, 0x00,
0x74, 0x00, 0x69, 0x00, 0x6f, 0x00, 0x6e, 0x00, 0x2e, 0x00,
0xa0, 0x82, 0x01, 0xc2, 0x30, 0x82, 0x01, 0xbe, 0x30, 0x82,
0x01, 0x68, 0xa0, 0x03, 0x02, 0x01, 0x02, 0x02, 0x10, 0x04,
0xd3, 0xc9, 0xdd, 0xb4, 0x38, 0x2a, 0xb5, 0x4d, 0x43, 0x4b,
0x99, 0x65, 0x19, 0xab, 0xeb, 0x30, 0x0d, 0x06, 0x09, 0x2a,
0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x04, 0x05, 0x00,
0x30, 0x16, 0x31, 0x14, 0x30, 0x12, 0x06, 0x03, 0x55, 0x04,
0x03, 0x13, 0x0b, 0x52, 0x6f, 0x6f, 0x74, 0x20, 0x41, 0x67,
0x65, 0x6e, 0x63, 0x79, 0x30, 0x1e, 0x17, 0x0d, 0x30, 0x33,
0x31, 0x32, 0x32, 0x36, 0x32, 0x32, 0x34, 0x35, 0x33, 0x37,
0x5a, 0x17, 0x0d, 0x33, 0x39, 0x31, 0x32, 0x33, 0x31, 0x32,
0x33, 0x35, 0x39, 0x35, 0x39, 0x5a, 0x30, 0x19, 0x31, 0x17,
0x30, 0x15, 0x06, 0x03, 0x55, 0x04, 0x03, 0x13, 0x0e, 0x4d,
0x65, 0x73, 0x73, 0x61, 0x67, 0x65, 0x53, 0x69, 0x67, 0x6e,
0x65, 0x72, 0x31, 0x30, 0x81, 0x9f, 0x30, 0x0d, 0x06, 0x09,
0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05,
0x00, 0x03, 0x81, 0x8d, 0x00, 0x30, 0x81, 0x89, 0x02, 0x81,
0x81, 0x00, 0x9b, 0xb4, 0x92, 0x23, 0x35, 0x3f, 0x23, 0xec,
0x4b, 0xcf, 0x4d, 0x5b, 0xed, 0x81, 0x22, 0x45, 0x62, 0x97,
0xea, 0x38, 0xff, 0x32, 0xc6, 0xa0, 0xdd, 0xeb, 0xd1, 0x18,
0x6a, 0x30, 0xec, 0x6e, 0x4b, 0x4f, 0xab, 0x2a, 0x41, 0xc7,
0x0d, 0xbb, 0xcd, 0x80, 0xdc, 0xef, 0xf2, 0xd0, 0x00, 0xd6,
0x82, 0x81, 0x7f, 0x9a, 0x9c, 0xc9, 0x41, 0xf3, 0xa8, 0x0b,
0xa3, 0x9d, 0xed, 0x9a, 0xee, 0x23, 0xb8, 0xf0, 0xe6, 0x27,
0x65, 0x30, 0x10, 0x13, 0x65, 0x75, 0x33, 0x64, 0x0b, 0x0b,
0xea, 0x7f, 0xf8, 0x3b, 0x49, 0xa7, 0xea, 0xd0, 0x2d, 0xc1,
0xf8, 0xa1, 0x66, 0xb9, 0x6d, 0xa2, 0x8d, 0x36, 0x43, 0x2e,
0xe1, 0x91, 0xe2, 0x41, 0xa1, 0xe6, 0x80, 0xc4, 0xa5, 0xf6,
0x1a, 0xa4, 0x1e, 0x1a, 0x47, 0x3e, 0x5e, 0xf1, 0x97, 0xc9,
0x26, 0x6a, 0x0c, 0xf1, 0x0f, 0xcb, 0x55, 0x03, 0xb2, 0xb7,
0x02, 0x03, 0x01, 0x00, 0x01, 0xa3, 0x4b, 0x30, 0x49, 0x30,
0x47, 0x06, 0x03, 0x55, 0x1d, 0x01, 0x04, 0x40, 0x30, 0x3e,
0x80, 0x10, 0x12, 0xe4, 0x09, 0x2d, 0x06, 0x1d, 0x1d, 0x4f,
0x00, 0x8d, 0x61, 0x21, 0xdc, 0x16, 0x64, 0x63, 0xa1, 0x18,
0x30, 0x16, 0x31, 0x14, 0x30, 0x12, 0x06, 0x03, 0x55, 0x04,
0x03, 0x13, 0x0b, 0x52, 0x6f, 0x6f, 0x74, 0x20, 0x41, 0x67,
0x65, 0x6e, 0x63, 0x79, 0x82, 0x10, 0x06, 0x37, 0x6c, 0x00,
0xaa, 0x00, 0x64, 0x8a, 0x11, 0xcf, 0xb8, 0xd4, 0xaa, 0x5c,
0x35, 0xf4, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
0xf7, 0x0d, 0x01, 0x01, 0x04, 0x05, 0x00, 0x03, 0x41, 0x00,
0x1c, 0x97, 0xe5, 0x69, 0xac, 0x34, 0xa5, 0xa0, 0xbb, 0xc5,
0x65, 0x2e, 0xdf, 0x14, 0xa8, 0x8d, 0x4e, 0xf1, 0x86, 0x6c,
0x05, 0x5f, 0x51, 0xf3, 0xcc, 0x09, 0x8e, 0xaa, 0xa9, 0x43,
0x85, 0x11, 0x3b, 0xa9, 0xc3, 0x7d, 0x46, 0x58, 0x6b, 0xae,
0xf5, 0x6b, 0xd4, 0xef, 0xdf, 0xa5, 0x0f, 0xdb, 0x37, 0x78,
0xfd, 0x79, 0xf3, 0x31, 0x61, 0x26, 0x44, 0x98, 0x8b, 0xa4,
0xab, 0x3a, 0x89, 0x6e, 0x31, 0x81, 0xcf, 0x30, 0x81, 0xcc,
0x02, 0x01, 0x01, 0x30, 0x2a, 0x30, 0x16, 0x31, 0x14, 0x30,
0x12, 0x06, 0x03, 0x55, 0x04, 0x03, 0x13, 0x0b, 0x52, 0x6f,
0x6f, 0x74, 0x20, 0x41, 0x67, 0x65, 0x6e, 0x63, 0x79, 0x02,
0x10, 0x04, 0xd3, 0xc9, 0xdd, 0xb4, 0x38, 0x2a, 0xb5, 0x4d,
0x43, 0x4b, 0x99, 0x65, 0x19, 0xab, 0xeb, 0x30, 0x09, 0x06,
0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x30, 0x0d,
0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,
0x01, 0x05, 0x00, 0x04, 0x81, 0x80, 0x4f, 0x71, 0x32, 0xc8,
0x5f, 0x2f, 0xe3, 0x8e, 0xc7, 0x8d, 0x85, 0x96, 0x28, 0x1d,
0x6e, 0xa6, 0x6e, 0x76, 0x63, 0x64, 0xae, 0x8d, 0xdc, 0x06,
0x64, 0x14, 0xeb, 0xcf, 0xcb, 0x2a, 0xd2, 0x17, 0xaa, 0xa5,
0x24, 0xd9, 0x17, 0x05, 0x07, 0x35, 0x8e, 0xa0, 0xce, 0x48,
0xed, 0x4b, 0x9d, 0xe4, 0x6c, 0xfa, 0xdc, 0x00, 0x82, 0x15,
0x6b, 0xde, 0x29, 0x90, 0x28, 0xe9, 0x53, 0xcb, 0x6b, 0xb7,
0xac, 0xa0, 0xf5, 0xd7, 0x75, 0x92, 0x89, 0x5e, 0x3d, 0x71,
0x46, 0x0c, 0x38, 0xee, 0xfb, 0x51, 0xfc, 0x4b, 0x7e, 0x70,
0x87, 0xde, 0x09, 0x8f, 0x0d, 0x63, 0x27, 0x26, 0x81, 0x43,
0xce, 0xcb, 0x03, 0x44, 0xe9, 0x70, 0xf5, 0xf0, 0x80, 0xcd,
0xe1, 0x89, 0x2b, 0xd8, 0x84, 0xd2, 0xc4, 0x90, 0xef, 0xbc,
0xad, 0x31, 0x2a, 0x3a, 0x29, 0xa0, 0xb0, 0x84, 0x9f, 0x65,
0x5b, 0x0d, 0x6f, 0x61};
Console.WriteLine("System.Security.Cryptography.Pkcs " +
"Sample: Multiple-signer signed " +
"and verified message");
Console.WriteLine("\n\n------------------------------");
Console.WriteLine(" SETUP OF CREDENTIALS ");
Console.WriteLine("------------------------------\n");
// Get the certificate of the additional message signer.
X509Certificate2Collection signerCerts = GetSignerCerts();
Console.WriteLine("\n\n----------------------");
Console.WriteLine(" SENDER SIDE ");
Console.WriteLine("----------------------\n");
// Decode the existing SignedCms message and add a signature
// to it.
byte[] encodedSignedCms = SignMsg(signedMessage, signerCerts);
Console.WriteLine("\n\n------------------------");
Console.WriteLine(" RECIPIENT SIDE ");
Console.WriteLine("------------------------\n");
// Verify all signatures in the message.
if (VerifyMsg(encodedSignedCms))
{
Console.WriteLine("\nMessage verified");
}
else
{
Console.WriteLine("\nMessage failed to verify");
}
}
// Open the My (or Personal) certificate store and search for
// credentials to sign the message with. There must be
// a certificate with subject name "MessageSigner2" in that
// certificate store.
static public X509Certificate2Collection GetSignerCerts()
{
// Open the My certificate store.
X509Store storeMy = new X509Store(StoreName.My,
StoreLocation.CurrentUser);
storeMy.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:", storeMy.Name.ToString());
foreach (X509Certificate2 cert in storeMy.Certificates)
{
Console.WriteLine("\t{0}", cert.SubjectName.Name);
}
// Find the signer's certificate.
// Add to the signers' certificate collection.
X509Certificate2Collection signerCertsColl =
storeMy.Certificates.Find(X509FindType.FindBySubjectName,
signerName, false);
Console.WriteLine(
"Found {0} certificates in the {1} store with name {2}",
signerCertsColl.Count, storeMy.Name, signerName);
// Check to see if the certificate suggested by the example
// requirements is not present.
if (signerCertsColl.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.");
}
storeMy.Close();
return signerCertsColl;
}
// Sign the message with the private key of the signer.
static public byte[] SignMsg(
Byte[] signedCmsMsg,
X509Certificate2Collection signerCerts)
{
// Instantiate a SignedCms object, and then decode the
// input encoded SignedCms message.
// Has default SubjectIdentifierType IssuerAndSerialNumber.
// Has default Detached property value false, so message is
// included in the encoded SignedCms.
SignedCms signedCms = new SignedCms();
signedCms.Decode(signedCmsMsg);
DisplaySignedCmsProperties("Original message", signedCms);
// Sign the PKCS #7/CMS message once for each
// signer certificate. In this example, one additional
// signer is added to the SignedCms object.
foreach (X509Certificate2 cert in signerCerts)
{
Console.Write("Computing signature with signer subject "
+ "name {0} ... ", cert.SubjectName.Name);
signedCms.ComputeSignature(new CmsSigner(cert));
Console.WriteLine("Done.");
}
DisplaySignedCmsProperties("Message with additional " +
"signer", signedCms);
// Encode the PKCS #7/CMS message.
return signedCms.Encode();
}
// Verify the encoded SignedCms message and return a Boolean
// value that specifies whether the verification was successful.
static public bool VerifyMsg(byte[] encodedSignedCms)
{
// Prepare an object in which to decode and verify.
SignedCms signedCms = new SignedCms();
signedCms.Decode(encodedSignedCms);
// Catch a verification exception if you want to
// advise the message recipient that security actions might
// be appropriate.
try
{
// Verify signature. Do not validate signer
// certificate chain for the purposes of this example.
// Note that in a production environment, validating
// the signer certificate chain will probably
// be necessary.
Console.Write("Checking signatures on message ... ");
signedCms.CheckSignature(true);
Console.WriteLine("Done.");
}
catch (System.Security.Cryptography.CryptographicException e)
{
Console.WriteLine("VerifyMsg caught exception: {0}",
e.Message);
Console.WriteLine("Verification of the signed PKCS #7 " +
"failed. The message, signatures, or " +
"countersignatures might have been modified " +
"in transit or storage. The message signers or " +
"countersigners might not be who they claim to be. " +
"The message's authenticity or integrity, or both, " +
"are not guaranteed.");
return false;
}
return true;
}
// This method displays some properties of a signed
// CMS/PKCS #7 message. These properties include the number of
// signers and countersigners for each signer, whether the
// message is detached, and the version of the message.
static void DisplaySignedCmsProperties(String info, SignedCms s)
{
Console.WriteLine();
Console.WriteLine("\n>>>>> SignedCms Signer Info: {0}", info);
Console.WriteLine("\tNumber of signers:\t\t\t{0}",
s.SignerInfos.Count);
for (int i = 0; i < s.SignerInfos.Count; i++)
{
Console.WriteLine("\tSubject name of signer #{0}:\t\t{1}",
i + 1, s.SignerInfos[i].Certificate.SubjectName.Name);
Console.WriteLine("\tNumber of countersigners for " +
"signer #{0}:\t{1}",
i + 1, s.SignerInfos[i].CounterSignerInfos.Count);
}
Console.WriteLine("\tMessage detached state:\t\t\t{0}",
s.Detached);
Console.WriteLine("\tMessage version:\t\t\t{0}", s.Version);
Console.WriteLine();
}
}
}
See Also
Tasks
How to: Sign Messages by One Signer
How to: Countersign a Message
How to: Envelope a Message for One Recipient
How to: Envelope a Message for Multiple Recipients