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HpkeDerivePrivateKey Method

Derive an EC private key in a deterministic manner from input keying material using the DeriveKeyPair algorithm in RFC9180.

Namespace: CryptoSysPKI
Assembly: diCrSysPKINet (in diCrSysPKINet.dll) Version: 23.0.0.30549 (23.1.0.0)
Syntax
Copy
public static string DerivePrivateKey(
	byte[] ikm,
	HpkeCurveName curveName,
	HpkeOutputOpts opts = HpkeOutputOpts.Default
)

Parameters

ikm  Byte
Input key material (ikm). This must have length in bytes at least as long as the key to be produced.
curveName  HpkeCurveName
Curve name
opts  HpkeOutputOpts  (Optional)
Output options (default=internal key format)

Return Value

String
Derived private key in string form or an empty string on error.
Remarks
By default the key is output as an ephemeral "internal" key string, which can be used directly with Ecc.SaveKey, Ecc.SaveEncKey, Ecc.PublicKeyFromPrivate, Ecc.DHSharedSecret and Ecc.QueryKey. If opts is set to `OutputOpts.KeyAsHex` then the key is output in serialized hexadecimal form in the same manner as the test vectors in [RFC9180] (without the clamping). The KDF to be used is fixed by the EC curve group as follows:
EC curveKDF
P-256HKDF-SHA256
P-384HKDF-SHA384
P-521HKDF-SHA512
X25519HKDF-SHA256
X448HKDF-SHA512
Example
C#
Copy
string ikmhex = "7268600d403fce431561aef583ee1613527cff655c1343f29812e66706df3234";
string skhex = Hpke.DerivePrivateKey(Cnv.FromHex(ikmhex), Hpke.CurveName.X25519, Hpke.OutputOpts.KeyAsHex);
// 52c4a758a802cd8b936eceea314432798d5baf2d7e9235dc084ab1b9cfa2f736
See Also