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c#encryptionkey-pairecdhprime256v1

c# generate key pair using ecdh prime256v1

I'm making private/public key using ecdh

var ecdh = new ECDiffieHellmanCng(CngKey.Create(CngAlgorithm.ECDiffieHellmanP256, null, new CngKeyCreationParameters { ExportPolicy = CngExportPolicies.AllowPlaintextExport }));
var privateKey = ecdh.Key.Export(CngKeyBlobFormat.EccPrivateBlob);
var publickey = ecdh.Key.Export(CngKeyBlobFormat.EccPublicBlob);

This code works fine, but I want to use Algorithm prime256v1 and CngAlgorithm has no such option. How can I do that ?

Solution

  • According to the docs, CngAlgorithm.ECDiffieHellmanP256 specifies the P-256 curve :

    An object that specifies an ECDH algorithm that uses the P-256 curve.

    This answer in crypto.stackexchange.com explains what those names come from different sources and that P-256 in NIST notation corresponds to prime256v1 in "ANSI X9.62 : Public Key Cryptography For The Financial Services Industry".