Hpke.LabeledExpand Method

Compute the output of the LabeledExpand function as defined in RFC9180.

Syntax

public static byte[] LabeledExpand(
   int numBytes,
   byte[] prk,
   string label,
   byte[] info,
   Hpke.CurveName curveName,
   Hpke.AeadAlg aeadAlg = Hpke.AeadAlg.None 
)

Public Shared Function LabeledExpand (
   numBytes As Integer,
   prk As Byte(),
   label As String,
   info As Byte(),
   curveName As Hpke.CurveName,
   Optional aeadAlg As Hpke.AeadAlg = Hpke.AeadAlg.None 
) As Byte()

Parameters

numBytes  Int32

Required number of bytes (L) of output keying material.

prk  Byte

Pseudorandom key (prk)

label  String

Label string

info  Byte

Byte string info

curveName  Hpke.CurveName

ECDH curve used in scheme

aeadAlg  Hpke.AeadAlg  (Optional)

AEAD encryption algorithm used in the scheme or 0 (default) to indicate KDF is being used inside a KEM algorithm.

Return Value

Remarks

Example

int Nk = 16;
// key = LabeledExpand(secret, 'key', key_schedule_context, Nk)
byte[] key = Hpke.LabeledExpand(Nk, Cnv.FromHex("12fff91991e93b48de37e7daddb52981084bd8aa64289c3788471d9a9712f397"), "key",
   Cnv.FromHex("00725611c9d98c07c03f60095cd32d400d8347d45ed67097bbad50fc56da742d07cb6cffde367bb0565ba28bb02c90744a20f5ef37f30523526106f637abb05449"),
   Hpke.CurveName.X25519, Hpke.AeadAlg.Aes_128_Gcm);
// 4531685d41d65f03dc48f6b8302c05b0

See Also

VB6/C equivalent: HPKE_LabeledExpand

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