有关在.net framework 4.7中执行ECDiffieHellmanCng的秘密协议的问题？

问题描述：

我有以下代码：有关在.net framework 4.7中执行ECDiffieHellmanCng的秘密协议的问题？

 var curve = ECCurve.NamedCurves.nistP256; 
     var ecdhSender = ECDiffieHellman.Create(curve); 
     var ecdhReceiver = ECDiffieHellman.Create(curve);

我的理解是，我应该能够计算秘密协议，无论是从使用ecdhSender对象使用ecdhReceiver.PublicKey或使用与ecdhSender.PublicKey ecdhReceiver对象和两个秘密协议值应相同。如果这是一个错误的假设，请让我知道。

由于ECDiffieHellman.Create返回ECDiffieHellman类型，我写了下面的代码来获取秘密协议：

 string receiverHexString = null; 
     using (SafeNCryptSecretHandle secretAgreement = (ecdhReceiver as ECDiffieHellmanCng).DeriveSecretAgreementHandle(ecdhSender.PublicKey)) 
     { 
      byte[] secretAgreementBytes = new byte[32]; 
      IntPtr pointer = secretAgreement.DangerousGetHandle(); 
      Marshal.Copy(pointer, secretAgreementBytes, 0, secretAgreementBytes.Length); 
      receiverHexString = BitConverter.ToString(secretAgreementBytes).Replace("-", string.Empty).ToLower(); 
      Console.WriteLine($"receiver secretAgreement: 0x{receiverHexString}"); 
     } 

     string senderHexString = null; 
     using (SafeNCryptSecretHandle secretAgreement = (ecdhSender as ECDiffieHellmanCng).DeriveSecretAgreementHandle(ecdhReceiver.PublicKey)) 
     { 
      byte[] secretAgreementBytes = new byte[32]; 
      IntPtr pointer = secretAgreement.DangerousGetHandle(); 
      Marshal.Copy(pointer, secretAgreementBytes, 0, secretAgreementBytes.Length); 
      senderHexString = BitConverter.ToString(secretAgreementBytes).Replace("-", string.Empty).ToLower(); 
      Console.WriteLine($"sender secretAgreement: 0x{senderHexString}"); 
     } 

     Assert.AreEqual(receiverHexString, senderHexString);

我断言失败。显然我做错了一些事情（如果秘密协议应该是相同的）。

难道我是如何提取字节的句柄吗？或者是其他东西？

你想完成什么？ NCRYPT_SECRET_HANDLE结构是不透明的，你不应该读它的内存。 – bartonjs

尝试使用详细步骤验证来自合作伙伴的结果。如果在我的问题的第一部分中，我的假设是正确的还是错误的，请您评论一下吗？ – Raghu

答

从last time I checked开始，没有文档记载的方式从CNG获取原始秘密协议值，这就是.NET不公开它的原因。

在.NET的预期使用ECDH的是

ECCurve curve = ECCurve.NamedCurves.nistP256; 

// Usually you'll only have one private key (yours), so this isn't representative of 
// real code. An `ECDiffieHellman` object doesn't necessarily have a private key, 
// but an `ECDiffieHellmanPublicKey` object definitely doesn't. 
using (ECDiffieHellman bobPrivate = ECDiffieHellman.Create(curve)) 
using (ECDiffieHellman alicePrivate = ECDiffieHellman.Create(curve)) 
using (ECDiffieHellmanPublicKey bobPublic = bobPrivate.PublicKey) 
using (ECDiffieHellmanPublicKey alicePublic = alicePrivate.PublicKey) 
{ 
    byte[] ba = bobPrivate.DeriveKeyFromHash(alicePublic, HashAlgorithmName.SHA256); 
    byte[] ab = alicePrivate.DeriveKeyFromHash(bobPublic, HashAlgorithmName.SHA256); 

    // ba and ab have the same contents. 
}

还有

DeriveKeyFromHash(ECDiffieHellmanPublicKey otherPartyPublicKey, HashAlgorithmName hashAlgorithm, byte[] secretPrepend, byte[] secretAppend)
DeriveKeyFromHmac(ECDiffieHellmanPublicKey otherPartyPublicKey, HashAlgorithmName hashAlgorithm, byte[] hmacKey)
DeriveKeyFromHmac(ECDiffieHellmanPublicKey otherPartyPublicKey, HashAlgorithmName hashAlgorithm, byte[] hmacKey, byte[] secretPrepend, byte[] secretAppend)
DeriveKeyTls(ECDiffieHellmanPublicKey otherPartyPublicKey, byte[] prfLabel, byte[] prfSeed)

如果bobPrivate和alicePublic（或者相反，alicePrivate和bobPublic）不变，那么提供相同的输入将产生相同的输出。

注意：你应该避免专门讨论ECDiffieHellmanCng，如果可以的话。当ECDH最终将其转换为.NET标准时，ECDHCng类不会。从.NET 4.6.2开始，一切都可以在基类上完成（打开持久键除外）;而.NET Core往往不会从其工厂方法中返回公共类型。

有关在.net framework 4.7中执行ECDiffieHellmanCng的秘密协议的问题？

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