/// <summary>
/// Sets ck, tempK = HKDF(ck, inputKeyMaterial, 2).
/// If HashLen is 64, then truncates tempK to 32 bytes.
/// Calls InitializeKey(tempK).
/// </summary>
public void MixKey(ReadOnlySpan <byte> inputKeyMaterial)
{
int length = inputKeyMaterial.Length;
Debug.Assert(length == 0 || length == Aead.KeySize || length == dh.DhLen);
Span <byte> output = stackalloc byte[2 * hash.HashLen];
hkdf.ExtractAndExpand2(ck, inputKeyMaterial, output);
output.Slice(0, hash.HashLen).CopyTo(ck);
var tempK = output.Slice(hash.HashLen, Aead.KeySize);
state.InitializeKey(tempK);
}
/// <summary>
/// Sets ck, tempK = HKDF(ck, inputKeyMaterial, 2).
/// If HashLen is 64, then truncates tempK to 32 bytes.
/// Calls InitializeKey(tempK).
/// </summary>
public unsafe void MixKey(byte *inputKeyMaterial, int inputKeyMaterialLength)
{
var length = inputKeyMaterialLength;
Debug.Assert(length == 0 || length == Aead.KeySize || length == dh.DhLen);
Span <byte> output = stackalloc byte[2 * hash.HashLen];
hkdf.ExtractAndExpand2(ck, hash.HashLen, inputKeyMaterial, inputKeyMaterialLength, output);
var slice = output.Slice(0, hash.HashLen);
for (var i = 0; i < hash.HashLen; i++)
{
ck[i] = slice[i];
}
var tempK = output.Slice(hash.HashLen, Aead.KeySize);
state.InitializeKey(tempK);
}
/// <summary>
/// Returns a pair of CipherState objects for encrypting transport messages.
/// </summary>
public (CipherState <CipherType> c1, CipherState <CipherType> c2) Split()
{
Span <byte> output = stackalloc byte[2 * hash.HashLen];
hkdf.ExtractAndExpand2(ck, null, output);
var tempK1 = output.Slice(0, Aead.KeySize);
var tempK2 = output.Slice(hash.HashLen, Aead.KeySize);
var c1 = new CipherState <CipherType>();
var c2 = new CipherState <CipherType>();
c1.InitializeKey(tempK1);
c2.InitializeKey(tempK2);
return(c1, c2);
}
