public PublicKey DerivePublickey(PublicKey basepoint, PublicKey perCommitmentPoint)
{
// TODO: pubkey = basepoint + SHA256(per_commitment_point || basepoint) * G
Span <byte> toHash = stackalloc byte[PublicKey.LENGTH * 2];
perCommitmentPoint.GetSpan().CopyTo(toHash);
basepoint.GetSpan().CopyTo(toHash.Slice(PublicKey.LENGTH));
byte[] hashed = NBitcoin.Crypto.Hashes.SHA256(toHash);
if (ECPubKey.TryCreate(basepoint, Context.Instance, out _, out ECPubKey? ecpubkey))
{
if (ecpubkey.TryAddTweak(hashed.AsSpan(), out ECPubKey? ecpubkeytweaked))
{
if (ecpubkeytweaked != null)
{
Span <byte> pub = stackalloc byte[33];
ecpubkeytweaked.WriteToSpan(true, pub, out _);
return(new PublicKey(pub.ToArray()));
}
}
}
return(null);
}
public PublicKey DeriveRevocationPublicKey(PublicKey basepoint, PublicKey perCommitmentPoint)
{
// TODO: revocationpubkey = revocation_basepoint * SHA256(revocation_basepoint || per_commitment_point) + per_commitment_point * SHA256(per_commitment_point || revocation_basepoint)
Span <byte> toHash1 = stackalloc byte[PublicKey.LENGTH * 2];
basepoint.GetSpan().CopyTo(toHash1);
perCommitmentPoint.GetSpan().CopyTo(toHash1.Slice(PublicKey.LENGTH));
byte[] hashed1 = NBitcoin.Crypto.Hashes.SHA256(toHash1);
ECPubKey?revocationBasepointTweaked = null;
if (ECPubKey.TryCreate(basepoint, Context.Instance, out _, out ECPubKey? ecbasepoint))
{
if (ecbasepoint.TryMultTweak(hashed1.AsSpan(), out ECPubKey? ecpubkeytweaked))
{
if (ecpubkeytweaked != null)
{
revocationBasepointTweaked = ecpubkeytweaked;
}
}
}
Span <byte> toHash2 = stackalloc byte[PublicKey.LENGTH * 2];
perCommitmentPoint.GetSpan().CopyTo(toHash2);
basepoint.GetSpan().CopyTo(toHash2.Slice(PublicKey.LENGTH));
byte[] hashed2 = NBitcoin.Crypto.Hashes.SHA256(toHash2);
ECPubKey?perCommitmentPointTweaked = null;
if (ECPubKey.TryCreate(perCommitmentPoint, Context.Instance, out _, out ECPubKey? ecperCommitmentPoint))
{
if (ecperCommitmentPoint.TryMultTweak(hashed2.AsSpan(), out ECPubKey? ecperCommitmentPointtweaked))
{
if (ecperCommitmentPointtweaked != null)
{
perCommitmentPointTweaked = ecperCommitmentPointtweaked;
}
}
}
if (revocationBasepointTweaked != null && perCommitmentPointTweaked != null)
{
var keys = new ECPubKey[] { revocationBasepointTweaked, perCommitmentPointTweaked };
if (ECPubKey.TryCombine(Context.Instance, keys, out ECPubKey? revocationpubkey))
{
if (revocationpubkey != null)
{
Span <byte> pub = stackalloc byte[33];
revocationpubkey.WriteToSpan(true, pub, out _);
return(new PublicKey(pub.ToArray()));
}
}
}
return(null);
}
public MusigPubNonce(Context?context, ReadOnlySpan <byte> in66)
{
if (!ECPubKey.TryCreate(in66.Slice(0, 33), context, out _, out var k1) ||
!ECPubKey.TryCreate(in66.Slice(33, 33), context, out _, out var k2))
{
throw new ArgumentException("Invalid musig pubnonce");
}
this.context = context ?? Context.Instance;
this.k1 = k1;
this.k2 = k2;
}
