CngAlgorithm.ECDiffieHellmanP521/P256/P384生成的EccPrivateBlob的CngKeyBlobFormat是什么？

Question

CngKey key = CngKey.Create(CngAlgorithm.ECDiffieHellmanP521, null,
   new CngKeyCreationParameters { ExportPolicy = CngExportPolicies.AllowPlaintextExport });    
byte[] keyBlob= key.Export(CngKeyBlobFormat.EccPrivateBlob);

keyBlob的长度是206，它的格式是什么？ 32字节的私钥和64字节的public密钥分别是哪些字节？

在Import a Public key from somewhere else to CngKey?，长度为4+4+64+32=104。

Answer 1

所有三条曲线的斑点二进制结构都相同：

<magic number, 4 bytes><modulus length in bytes, 4 bytes><x-value of public key><y-value of public key><private key>

详细适用：

secp256r1 / NIST P-256

Private: 45434B32 20000000 <x-value of public key, 32 bytes><y-value of public key, 32 bytes><private key, 32 bytes>   total length: 104 bytes
Public:  45434B31 20000000 <x-value of public key, 32 bytes><y-value of public key, 32 bytes>                          total length:  72 bytes

secp384r1/NIST P-384

Private: 45434B34 30000000 <x-value of public key, 48 bytes><y-value of public key, 48 bytes><private key, 48 bytes>   total length: 152 bytes
Public:  45434B33 30000000 <x-value of public key, 48 bytes><y-value of public key, 48 bytes>                          total length: 104 bytes

secp521r1 / NIST P-521

Private: 45434B36 42000000 <x-value of public key, 66 bytes><y-value of public key, 66 bytes><private key, 66 bytes>   total length: 206 bytes
Public:  45434B35 42000000 <x-value of public key, 66 bytes><y-value of public key, 66 bytes>                          total length: 140 bytes

私钥和 public 密钥的 x- 和 y- 组件以大端格式存储。所有三个分量都具有模数的长度。因此，斑点的不同长度是由曲线的不同模量引起的。

另请参阅：SECG, SEC2, key blob format, magic numbers, format of ECCPublicBlob and ECCPrivateBlob

CngAlgorithm.ECDiffieHellmanP521/P256/P384生成的EccPrivateBlob的CngKeyBlobFormat是什么？

what is the CngKeyBlobFormat of EccPrivateBlob generated by CngAlgorithm.ECDiffieHellmanP521/P256/P384?

c#

cng

ecdh