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[英]Importing an Objective-C RSA public key into c# RSACryptoServiceProvider
[英]C# - importing a public key blob into ECDiffieHellmanCng
我在使用ECDiffieHellmanCng类交换密钥时遇到了麻烦:
第1步-创建公钥
public byte[] CreatePublicKey()
{
using (ECDiffieHellmanCng cng = new ECDiffieHellmanCng())
{
cng.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
cng.HashAlgorithm = CngAlgorithm.Sha512;
return cng.PublicKey.ToByteArray();
}
}
第2步-交换并获取私钥
public byte[] CreatePrivateKey(byte[] publicKey1, byte[] publicKey2)
{
using(ECDiffieHellmanCng cng = new ECDiffieHellmanCng(CngKey.Import(publicKey1, CngKeyBlobFormat.EccPublicBlob)))
{
cng.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
cng.HashAlgorithm = CngAlgorithm.Sha512;
return cng.DeriveKeyMaterial(CngKey.Import(publicKey2, CngKeyBlobFormat.EccPublicBlob));
}
}
例
byte[] alicePublicKey = CreatePublicKey();
byte[] bobPublicKey = CreatePublicKey();
// This fails
byte[] alicePrivateKey = CreatePrivateKey(alicePublicKey, bobPublicKey);
byte[] bobPrivateKey = CreatePrivateKey(bobPublicKey, alicePublicKey);
具体来说,它无法通过CreatePrivateKey(...)
方法在此行上执行:
return cng.DeriveKeyMaterial(CngKey.Import(publicKey2, CngKeyBlobFormat.EccPublicBlob));
错误
System.Security.Cryptography.CryptographicException:'密钥不存在。
我究竟做错了什么?
问题是您正在尝试使用两个公用密钥派生共享秘密( DeriveKeyMaterial
结果)。 这将行不通,因为您需要一个方的私钥和另一方的公钥(不需要第一方的公钥,因为它可以从私钥派生)。 这是一个示例(我固定了一些术语,因为现在它们具有误导性CreatePrivateKey
不会创建私钥)。 请注意,您通常不会像这样导出私钥,而是将其存储在容器中,因此仅举例来说:
public static (byte[] publicKey, byte[] privateKey) CreateKeyPair() {
using (ECDiffieHellmanCng cng = new ECDiffieHellmanCng(
// need to do this to be able to export private key
CngKey.Create(
CngAlgorithm.ECDiffieHellmanP256,
null,
new CngKeyCreationParameters
{ ExportPolicy = CngExportPolicies.AllowPlaintextExport }))) {
cng.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
cng.HashAlgorithm = CngAlgorithm.Sha512;
// export both private and public keys and return
var pr = cng.Key.Export(CngKeyBlobFormat.EccPrivateBlob);
var pub = cng.PublicKey.ToByteArray();
return (pub, pr);
}
}
public static byte[] CreateSharedSecret(byte[] privateKey, byte[] publicKey) {
// this returns shared secret, not private key
// initialize algorithm with private key of one party
using (ECDiffieHellmanCng cng = new ECDiffieHellmanCng(CngKey.Import(privateKey, CngKeyBlobFormat.EccPrivateBlob))) {
cng.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
cng.HashAlgorithm = CngAlgorithm.Sha512;
// use public key of another party
return cng.DeriveKeyMaterial(CngKey.Import(publicKey, CngKeyBlobFormat.EccPublicBlob));
}
}
现在具有以上两个功能:
var aliceKeyPair = CreateKeyPair();
var bobKeyPair = CreateKeyPair();
byte[] bobSharedSecret = CreateSharedSecret(bobKeyPair.privateKey, aliceKeyPair.publicKey);
byte[] aliceSharedSecret = CreateSharedSecret(aliceKeyPair.privateKey, bobKeyPair.publicKey);
// derived shared secrets are the same - the whole point of this algoritm
Debug.Assert(aliceSharedSecret.SequenceEqual(bobSharedSecret));
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