MimbleWimble(Tests): addressed comments

Addressed code review comments. Added latest Fsdk package in
order to use BetterAssert function.

src/NLitecoin/MimbleWimble/EC.fs

@@ -8,7 +8,7 @@ open Org.BouncyCastle.Math
 open Org.BouncyCastle.Math.EC
 open Org.BouncyCastle.Crypto.Digests
 
-let curve = ECNamedCurveTable.GetByName("secp256k1")
+let curve = ECNamedCurveTable.GetByName "secp256k1"
 let domainParams = new ECDomainParameters(curve.Curve, curve.G, curve.N, curve.H, curve.GetSeed())
 
 // see https://github.com/bitcoin-core/secp256k1/issues/1180#issuecomment-1356859346
@@ -42,7 +42,8 @@ type BigInteger with
 
 type NBitcoin.Secp256k1.ECPrivKey with
     member self.ToBytes() =
-        let bytes = Array.zeroCreate 32
+        let numBytesInPrivateKey = 32
+        let bytes = Array.zeroCreate numBytesInPrivateKey
         self.WriteToSpan(bytes.AsSpan())
         bytes
 
@@ -88,28 +89,31 @@ let IsQuadVar (elem: ECFieldElement) =
         Jakobi elem >= 0
 
 let SchnorrSign (key: array<byte>) (msgHash: array<byte>) : Signature =
+    let numBytesInSha256 = 32
     let k0 = 
         let hasher = Sha256Digest()
         hasher.BlockUpdate(key, 0, key.Length)
         hasher.BlockUpdate(msgHash, 0, msgHash.Length)
-        let arr = Array.zeroCreate 32
+        let arr = Array.zeroCreate numBytesInSha256
         hasher.DoFinal(arr, 0) |> ignore
         BigInteger.FromByteArrayUnsigned(arr).Mod(scalarOrder)
 
     if k0 = BigInteger.Zero then
         failwith "Failure. This happens only with negligible probability."
 
     let keyScalar = BigInteger.FromByteArrayUnsigned key
-    assert(keyScalar < scalarOrder)
+    Fsdk.Misc.BetterAssert (keyScalar < scalarOrder) "key is not in range [0; scalarOrder)"
 
     let R = generatorG.Multiply(k0).Normalize()
     let k = if Jakobi R.AffineYCoord <> 1 then scalarOrder.Subtract k0 else k0
     let e = 
         let hasher = Sha256Digest()
-        hasher.BlockUpdate(R.AffineXCoord.GetEncoded(), 0, 32)
-        hasher.BlockUpdate(generatorG.Multiply(keyScalar).GetEncoded(true), 0, 33)
+        let xEncoded = R.AffineXCoord.GetEncoded()
+        hasher.BlockUpdate(xEncoded, 0, xEncoded.Length)
+        let keyScalarTimesGEncoded = generatorG.Multiply(keyScalar).GetEncoded(true)
+        hasher.BlockUpdate(keyScalarTimesGEncoded, 0, keyScalarTimesGEncoded.Length)
         hasher.BlockUpdate(msgHash, 0, msgHash.Length)
-        let arr = Array.zeroCreate 32
+        let arr = Array.zeroCreate numBytesInSha256
         hasher.DoFinal(arr, 0) |> ignore
         BigInteger.FromByteArrayUnsigned(arr).Mod(scalarOrder)
 

src/NLitecoin/MimbleWimble/Pedersen.fs

@@ -28,7 +28,7 @@ let DeserializeCommitment (commitment: PedersenCommitment) : ECPoint =
         point
 
 /// Generates a pedersen commitment: *commit = blind * G + value * H. The blinding factor is 32 bytes.
-let Commit (value: CAmount) (blind: BlindingFactor) : PedersenCommitment =
+let Commit (value: Amount) (blind: BlindingFactor) : PedersenCommitment =
     let result =
         let blind = blind.ToUInt256().ToBytes() |> BigInteger.FromByteArrayUnsigned
         let a = generatorG.Multiply(blind)
@@ -39,7 +39,7 @@ let Commit (value: CAmount) (blind: BlindingFactor) : PedersenCommitment =
     PedersenCommitment(BigInt bytes)
 
 /// Calculates the blinding factor x' = x + SHA256(xG+vH | xJ), used in the switch commitment x'G+vH.
-let BlindSwitch (blindingFactor: BlindingFactor) (amount: CAmount) : BlindingFactor =
+let BlindSwitch (blindingFactor: BlindingFactor) (amount: Amount) : BlindingFactor =
     let hasher = Sha256Digest()
 
     let x = blindingFactor.ToUInt256().ToBytes() |> BigInteger.FromByteArrayUnsigned

src/NLitecoin/MimbleWimble/TransactionBuilder.fs

@@ -249,17 +249,23 @@ let private CreateOutputs (recipients: seq<Recipient>) : Outputs =
 let private CreateKernel
     (blind: BlindingFactor) 
     (stealthBlind: BlindingFactor) 
-    (fee: CAmount)
-    (peginAmount: Option<CAmount>)
+    (fee: Amount)
+    (peginAmount: Option<Amount>)
     (pegouts: array<PegOutCoin>) 
     : Kernel =
     let featuresByte =
-        (if fee > 0L then KernelFeatures.FEE_FEATURE_BIT else enum 0) |||
-        (match peginAmount with 
-            | Some value when value > 0L -> KernelFeatures.PEGIN_FEATURE_BIT 
-            | _ -> enum 0) |||
-        (if pegouts.Length > 0 then KernelFeatures.PEGOUT_FEATURE_BIT else enum 0) |||
-        KernelFeatures.STEALTH_EXCESS_FEATURE_BIT
+        (if fee > 0L then
+             KernelFeatures.FEE_FEATURE_BIT
+         else
+             enum 0)
+        ||| (match peginAmount with
+             | Some value when value > 0L -> KernelFeatures.PEGIN_FEATURE_BIT
+             | _ -> enum 0)
+        ||| (if pegouts.Length > 0 then
+                 KernelFeatures.PEGOUT_FEATURE_BIT
+             else
+                 enum 0)
+        ||| KernelFeatures.STEALTH_EXCESS_FEATURE_BIT
 
     let excessCommit = Pedersen.Commit 0L blind
 
@@ -278,14 +284,14 @@ let private CreateKernel
         let stream = BitcoinStream(byteStream, true)
 
         stream.ReadWrite (featuresByte |> uint8) |> ignore
-        Helpers.write stream excessCommit
+        Helpers.Write stream excessCommit
         stream.ReadWriteAsVarInt (fee |> uint64 |> ref)
         match peginAmount with
         | Some amount -> stream.ReadWriteAsVarInt (amount |> uint64 |> ref)
         | None -> ()
         if pegouts.Length > 0 then
-            Helpers.writeArray stream pegouts
-        Helpers.write stream (BigInt stealthExcess)
+            Helpers.WriteArray stream pegouts
+        Helpers.Write stream (BigInt stealthExcess)
 
         let hasher = Hasher()
         hasher.Write(byteStream.ToArray())
@@ -312,8 +318,8 @@ let BuildTransaction
     (inputCoins: array<Coin>)
     (recipients: array<Recipient>)
     (pegouts: array<PegOutCoin>)
-    (peginAmount: Option<CAmount>)
-    (fee: CAmount)
+    (peginAmount: Option<Amount>)
+    (fee: Amount)
     : TransactionBuildResult =
     let pegoutTotal = pegouts |> Array.sumBy (fun pegout -> pegout.Amount)
     let recipientTotal = recipients |> Array.sumBy (fun recipient -> recipient.Amount)
@@ -328,7 +334,7 @@ let BuildTransaction
                 pegoutTotal
                 recipientTotal
                 fee)
-        raise (IncorrectBalanceException msg)
+        raise <| IncorrectBalanceException msg
 
     let inputs = CreateInputs inputCoins
     let outputs = CreateOutputs recipients