Question

我有以下代码：

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

我的理解是，我应该能够通过使用ecdhReceiver.PublicKey使用ecdhSender对象或使用ecdhSender.PublicKey使用ecdhReceiver对象来计算秘密协议，并且两个秘密协议值应该相同。如果这是一个错误的假设，请告诉我。

由于ECDiffieHellman.Create返回ECDiffieHellman类型，我编写了以下代码以获取秘密协议：

        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);

我的断言失败了。显然我做错了（如果秘密协议应该是相同的）。

我是如何从句柄中提取字节的？或其他什么？

Answer 1

从last time I checked开始，没有记录的方法可以从CNG获取原始秘密协议值，这就是.NET不公开它的原因。

.NET中预期使用ECDH

"click_id and number"

还有

created_at and timestamp
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. }
DeriveKeyFromHash(ECDiffieHellmanPublicKey otherPartyPublicKey, HashAlgorithmName hashAlgorithm, byte[] secretPrepend, byte[] secretAppend)
DeriveKeyFromHmac(ECDiffieHellmanPublicKey otherPartyPublicKey, HashAlgorithmName hashAlgorithm, byte[] hmacKey)

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

注意：如果可以的话，你应该避免具体谈论DeriveKeyFromHmac(ECDiffieHellmanPublicKey otherPartyPublicKey, HashAlgorithmName hashAlgorithm, byte[] hmacKey, byte[] secretPrepend, byte[] secretAppend)。当ECDH最终进入.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（除了打开持久化键）;并且.NET Core倾向于不从其DeriveKeyTls(ECDiffieHellmanPublicKey otherPartyPublicKey, byte[] prfLabel, byte[] prfSeed)工厂方法返回公共类型。

关于ECDiffieHellmanCng在.net framework 4.7中实现的秘密协议的问题？

1 个答案: