生成的 ECDsaCng 密钥长于预期的 32 字节

Question

我在摆弄 ECDsaCng，发现密钥大小似乎不正确。从下面的代码来看，privateKey 变量，例如，是一个 104 字节长的数组，而我没想到它会大于 32。

我做错了什么？

        ECDsaCng dsa = new ECDsaCng(256);
        dsa.HashAlgorithm = CngAlgorithm.Sha256;
        dsa.GenerateKey(ECCurve.NamedCurves.nistP256);
        var privateKey = dsa.Key.Export(CngKeyBlobFormat.EccPrivateBlob);
        var publicKey = dsa.Key.Export(CngKeyBlobFormat.EccPublicBlob);

提前致谢。

Answer 1

私钥d是[1, n - 1]中的一个随机整数，其中n是基点G的顺序。 public键是曲线点(x, y) = d * G、here. For NIST P-256 (secp256r1) d、x和y被编码为32字节（值不能更大）。

MS 以 here. The format for the public key has an 8 bytes header, followed by the 32 bytes x-value and the 32 bytes y-value, so that the total length is 72 bytes. The format for the private key has a (different) 8-byte header, followed by the 32 byte x-value, the 32 byte y-value, and the 32 byte d-value, so that the total length is 104 bytes, in accordance with the value you found. A detailed description of the headers can be found here.

描述的特定格式存储这两个密钥

生成的 ECDsaCng 密钥长于预期的 32 字节

ECDsaCng key generated longer than expected 32-bytes

c#

ecdsa