使用X509證書對多個收件人進行XML加密和解密

Question

我已經設法使用MSDN上的示例加密和解密xml文檔。 http://msdn.microsoft.com/en-us/library/ms229744.aspx和http://msdn.microsoft.com/en-us/library/ms229943.aspx

這都是根據W3C XML加密標准（XML Enc）完成的。

這一切都很好。 我的問題是一個xml文檔適用於2或3個收件人。 我想用多個密鑰（X509證書公鑰）加密相同的xml，以便多個收件人可以解密文檔。

根據W3C XML加密標准，通過使用包含加密對稱會話密鑰的多個EncryptionKey元素，這一切都是可能的。

我找不到任何關於如何使用標准加密類在.Net中實現此目的的示例。

這必須在.NET C＃中實現。

有沒有辦法在某處做這個或代碼示例？

Answer 1

EncryptedElement類可以根據需要使用盡可能多的EncryptedKeys。 只要對方能夠正確識別他們的EncryptedKey（使用Recipient或KeyInfoName元素），就不應該有任何問題：

// example xml
XmlDocument xdoc = new XmlDocument();
xdoc.PreserveWhitespace = true;
xdoc.LoadXml(@"<root><encryptme>hello world</encryptme></root>");

var elementToEncrypt = (XmlElement)xdoc.GetElementsByTagName("encryptme")[0];

// keys
// rsa keys would normally be pulled from a store
RSA rsaKey1 = new RSACryptoServiceProvider();
RSA rsaKey2 = new RSACryptoServiceProvider();
var publicKeys = new[] { rsaKey1, rsaKey2 };

string sessKeyName = "helloworldkey";
var sessKey = new RijndaelManaged() { KeySize = 256 };

// encrypt
var encXml = new EncryptedXml();
var encryptedElement = new EncryptedData()
{
    Type = EncryptedXml.XmlEncElementUrl,
    EncryptionMethod = new EncryptionMethod(EncryptedXml.XmlEncAES256Url),
    KeyInfo = new KeyInfo()
};
encryptedElement.CipherData.CipherValue = encXml.EncryptData(elementToEncrypt, sessKey, false);
encryptedElement.KeyInfo.AddClause(new KeyInfoName(sessKeyName));

// encrypt the session key and add keyinfo's
int keyID = 0;
foreach (var pk in publicKeys)
{
    var encKey = new EncryptedKey()
    {
        CipherData = new CipherData(EncryptedXml.EncryptKey(sessKey.Key, pk, false)),
        EncryptionMethod = new EncryptionMethod(EncryptedXml.XmlEncRSA15Url),
        Recipient = string.Format("recipient{0}@foobar.com", ++keyID),
        CarriedKeyName = sessKeyName,
    };
    encKey.KeyInfo.AddClause(new KeyInfoName(encKey.Recipient));
    encryptedElement.KeyInfo.AddClause(new KeyInfoEncryptedKey(encKey));
}

// update the xml
EncryptedXml.ReplaceElement(elementToEncrypt, encryptedElement, false);

// show the result
Console.Write(xdoc.InnerXml);
Console.ReadLine();
Console.WriteLine(new string('-', 80));

產生

<root>
    <EncryptedData Type="http://www.w3.org/2001/04/xmlenc#Element" xmlns="http://www.w3.org/2001/04/xmlenc#">
        <EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes256-cbc" />
        <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
            <KeyName>helloworldkey</KeyName>
            <EncryptedKey Recipient="recipient1@foobar.com" xmlns="http://www.w3.org/2001/04/xmlenc#">
                <EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-1_5" />
                <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
                    <KeyName>recipient1@foobar.com</KeyName>
                </KeyInfo>
                <CipherData>
                    <CipherValue>bmVT4SuAgWto6NJoTnUhrwaQ5/bWx39WKfs8y/QEQbaEBqdvl2Wa3woQGZxfigZ2wsWZQJFW0YGMII0W6AATnsqGOOVEbdGxmnvXRISiRdhcyNHkHot0kDK987y446ws5CZQQuz8inGq/SNrhiK6RyVnBE4ykWjrJyIS5wScwqA=</CipherValue>
                </CipherData>
                <CarriedKeyName>helloworldkey</CarriedKeyName>
            </EncryptedKey>
            <EncryptedKey Recipient="recipient2@foobar.com" xmlns="http://www.w3.org/2001/04/xmlenc#">
                <EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-1_5" />
                <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
                    <KeyName>recipient2@foobar.com</KeyName>
                </KeyInfo>
                <CipherData>
                    <CipherValue>oR8NPTm1NasWeDXBjayLk+p9/5RTWOZwNJHUMTQpZB9v1Aasi75oSjGqSqN0HMTiviw6NWz8AvHB9+i08L4Hw8JRDLxZgjaKqTGu31wXmM3Vc0CoYQ15AWMZN4q4tSxDhwuT8fp9SN+WFBm+M3w3bcPoooAazzDHK3ErzfXzYiU=</CipherValue>
                </CipherData>
                <CarriedKeyName>helloworldkey</CarriedKeyName>
            </EncryptedKey>
        </KeyInfo>
        <CipherData>
            <CipherValue>ohjWIEFf2WO6v/CC+ugd7uxEKGJlxgdT9N+t3MhoTIyXHqT5VlknWs0XlAhcgajkxKFjwVO3p413eRSMTLXKCg==</CipherValue>
        </CipherData>
    </EncryptedData>
</root>

要解密文檔，您必須提供密鑰名稱和證書私鑰之間的映射：

// Decrypt
string myKeyName = "recipient1@foobar.com";

// specify we want to use the key for recipient1
var encryptedDoc = new EncryptedXml(xdoc);
encryptedDoc.AddKeyNameMapping(myKeyName, rsaKey1);
encryptedDoc.Recipient = myKeyName;

// Decrypt the element.
encryptedDoc.DecryptDocument();

// show the result
Console.Write(xdoc.InnerXml);
Console.ReadLine();

結果：

<root><encryptme>hello world</encryptme></root>