Backend: addressed comments

Refactoring: addressed comments to the PR.

Author: webwarrior-ws

src/GWallet.Backend.Tests/SilentPayments.fs

@@ -76,7 +76,7 @@ type SilentPayments() =
                                     let stream = BitcoinStream(DataEncoders.Encoders.Hex.DecodeData hex)
                                     Some <| WitScript.Load stream
                             let spInput =
-                                SilentPayments.convertToSilentPaymentInput 
+                                SilentPayments.ConvertToSilentPaymentInput 
                                     (Script.FromHex input.ScriptPubKey) 
                                     (DataEncoders.Encoders.Hex.DecodeData input.ScriptSig)
                                     witness
@@ -104,9 +104,9 @@ type SilentPayments() =
                 | [], Some _ ->
                     Assert.Fail(sprintf "No inputs for shared secret derivation in test case '%s'" testCaseName)
                 | _, Some expectedOutputString ->
-                    let output = SilentPayments.createOutput privateKeys outpoints recipients.[0]
+                    let output = SilentPayments.CreateOutput privateKeys outpoints recipients.[0]
                     let outputString = output.GetEncoded() |> DataEncoders.Encoders.Hex.EncodeData
                     Assert.AreEqual(expectedOutputString, outputString, sprintf "Failure in test case '%s'" testCaseName)
                 | _, None ->
-                    Assert.Throws(fun () -> SilentPayments.createOutput privateKeys outpoints recipients.[0] |> ignore)
+                    Assert.Throws(fun () -> SilentPayments.CreateOutput privateKeys outpoints recipients.[0] |> ignore)
                     |> ignore

src/GWallet.Backend/UtxoCoin/SilentPayments.fs

@@ -29,6 +29,10 @@ type SilentPaymentAddress =
     static member MainNetPrefix = "sp"
     static member TestNetPrefix = "tsp"
 
+    // https://github.com/bitcoin/bips/blob/master/bip-0352.mediawiki#address-encoding
+    static member MinimumEncodedLength = 116u
+    static member MaximumEncodedLength = 1023u
+
     static member private GetEncoder(chainName: ChainName) =
         let hrp =
             if chainName = ChainName.Mainnet then
@@ -81,20 +85,20 @@ type SilentPaymentInput =
     | InputJustForSpending
 
 module SilentPayments =
-    let private secp256k1 = EC.CustomNamedCurves.GetByName("secp256k1")
+    let private secp256k1 = EC.CustomNamedCurves.GetByName "secp256k1"
 
     let private scalarOrder = BigInteger("fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141", 16)
 
-    let private NUMS_H_bytes = 
+    let private NUMS_H_BYTES = 
         [| 0x50uy; 0x92uy; 0x9buy; 0x74uy; 0xc1uy; 0xa0uy; 0x49uy; 0x54uy; 0xb7uy; 0x8buy; 0x4buy; 0x60uy; 0x35uy; 0xe9uy; 0x7auy; 0x5euy;
            0x07uy; 0x8auy; 0x5auy; 0x0fuy; 0x28uy; 0xecuy; 0x96uy; 0xd5uy; 0x47uy; 0xbfuy; 0xeeuy; 0x9auy; 0xceuy; 0x80uy; 0x3auy; 0xc0uy; |]
 
-    type BigInteger with
-        static member FromByteArrayUnsigned (bytes: array<byte>) =
+    module BigInteger =
+        let FromByteArrayUnsigned (bytes: array<byte>) =
             BigInteger(1, bytes)
 
     // see https://github.com/bitcoin/bips/blob/master/bip-0352.mediawiki#selecting-inputs
-    let convertToSilentPaymentInput (scriptPubKey: Script) (scriptSig: array<byte>) (witness: Option<WitScript>): SilentPaymentInput =
+    let ConvertToSilentPaymentInput (scriptPubKey: Script) (scriptSig: array<byte>) (witness: Option<WitScript>): SilentPaymentInput =
         if scriptPubKey.IsScriptType ScriptType.P2PKH then
             // skip the first 3 op_codes and grab the 20 byte hash
             // from the scriptPubKey
@@ -144,7 +148,7 @@ module SilentPayments =
                         let controlBlock = witnessStack.Peek()
                         //  controlBlock is <control byte> <32 byte internal key> and 0 or more <32 byte hash>
                         let internalKey = controlBlock.[1..32]
-                        internalKey = NUMS_H_bytes
+                        internalKey = NUMS_H_BYTES
                     else
                         false
                 if internalKeyIsH then
@@ -165,7 +169,7 @@ module SilentPayments =
         else
             InvalidInput
 
-    let taggedHash (tag: string) (data: array<byte>) : array<byte> =
+    let TaggedHash (tag: string) (data: array<byte>) : array<byte> =
         let sha256 = Digests.Sha256Digest()
 
         let tag = Text.ASCIIEncoding.ASCII.GetBytes tag
@@ -181,12 +185,12 @@ module SilentPayments =
         sha256.DoFinal(result, 0) |> ignore
         result
 
-    let getInputHash (outpoints: List<OutPoint>) (sumInputPubKeys: EC.ECPoint) : array<byte> =
+    let GetInputHash (outpoints: List<OutPoint>) (sumInputPubKeys: EC.ECPoint) : array<byte> =
         let lowestOutpoint = outpoints |> List.map (fun outpoint -> outpoint.ToBytes()) |> List.min
         let hashInput = Array.append lowestOutpoint (sumInputPubKeys.GetEncoded true)
-        taggedHash "BIP0352/Inputs" hashInput
+        TaggedHash "BIP0352/Inputs" hashInput
 
-    let createOutput (privateKeys: List<Key * bool>) (outpoints: List<OutPoint>) (spAddress: SilentPaymentAddress) =
+    let CreateOutput (privateKeys: List<Key * bool>) (outpoints: List<OutPoint>) (spAddress: SilentPaymentAddress) =
         if privateKeys.IsEmpty then
             failwith "privateKeys should not be empty"
 
@@ -211,7 +215,7 @@ module SilentPayments =
         if aSum = BigInteger.Zero then
             failwith "Input privkeys sum is zero"
 
-        let inputHash = getInputHash outpoints (secp256k1.G.Multiply aSum)
+        let inputHash = GetInputHash outpoints (secp256k1.G.Multiply aSum)
 
         let tweak = BigInteger.FromByteArrayUnsigned inputHash
         let tweakedSumSeckey = aSum.Multiply(tweak).Mod(scalarOrder)
@@ -220,11 +224,21 @@ module SilentPayments =
 
         let k = 0u
         let tK =
-            taggedHash
+            TaggedHash
                 "BIP0352/SharedSecret"
                 (Array.append (ecdhSharedSecret.GetEncoded true) (BitConverter.GetBytes k))
                 |> BigInteger.FromByteArrayUnsigned
-        let Bm = secp256k1.Curve.DecodePoint <| spAddress.SpendPublicKey.ToBytes()
-        let sharedSecret = Bm.Add(secp256k1.G.Multiply tK)
+        let bM = secp256k1.Curve.DecodePoint <| spAddress.SpendPublicKey.ToBytes()
+        let sharedSecret = bM.Add(secp256k1.G.Multiply tK)
 
         sharedSecret.Normalize().AffineXCoord
+
+    let GetFinalDestination (privateKey: Key) (outpoints: List<OutPoint>) (destination: string) (network: Network) : string =
+        let privateKeys = 
+            outpoints 
+            |> List.map (fun _ -> (privateKey, false))
+
+        let output = CreateOutput privateKeys outpoints (SilentPaymentAddress.Decode destination)
+        let taprootAddress = TaprootAddress(TaprootPubKey(output.GetEncoded()), network)
+
+        taprootAddress.ToString()

src/GWallet.Backend/UtxoCoin/UtxoCoinAccount.fs

@@ -291,7 +291,7 @@ module Account =
 
     let private CalculateSilentPaymentDestination (account: IUtxoAccount)
                                                   (transactionInputs: List<TransactionInputOutpointInfo>)
-                                                  (destination: string)
+                                                  (reusableAddress: string)
                                                   (privateKey: Key) =
         // Since we can only receive P2WPKH-P2SH or P2WPKH transactions, and
         // non-compressed keys are not accepted as default policy
@@ -302,15 +302,8 @@ module Account =
         let outpoints = 
             transactionInputs
             |> List.map (fun input -> (ConvertToICoin account input).Outpoint)
-
-        let privateKeys = 
-            outpoints 
-            |> List.map (fun _ -> (privateKey, false))
-
-        let output = SilentPayments.createOutput privateKeys outpoints (SilentPaymentAddress.Decode destination)
-        let taprootAddress = TaprootAddress(TaprootPubKey(output.GetEncoded()), GetNetwork (account:>IAccount).Currency)
-
-        taprootAddress.ToString()
+        
+        SilentPayments.GetFinalDestination privateKey outpoints reusableAddress (GetNetwork (account:>IAccount).Currency)
 
     let private CheckSilentPaymentTransactionInputValidity (finalTransaction: Transaction) 
                                                            (txMetadataInputs: List<TransactionInputOutpointInfo>) =
@@ -324,11 +317,11 @@ module Account =
                 | None -> failwith (SPrintF1 "Could not find output with index=%d in txMetadataInputs" input.PrevOut.N)
             let scriptPubKey =
                 Script(NBitcoin.DataEncoders.Encoders.Hex.DecodeData inputOutpointInfo.DestinationInHex)
-            match SilentPayments.convertToSilentPaymentInput scriptPubKey (input.ScriptSig.ToBytes()) (Some input.WitScript) with
+            match SilentPayments.ConvertToSilentPaymentInput scriptPubKey (input.ScriptSig.ToBytes()) (Some input.WitScript) with
             | InputForSharedSecretDerivation _ -> ()
             | _ -> 
                 let errorMessage = SPrintF1 "One of the inputs is not valid for shared secret derivation: %A" inputOutpointInfo
-                failwith ("Error creating silent payment transaction:\n" + errorMessage)
+                failwith (SPrintF1 "Error creating silent payment transaction: %s" errorMessage)
 
     let internal EstimateTransferFee
         (account: IUtxoAccount)
@@ -427,7 +420,7 @@ module Account =
                 raise <| Exception(SPrintF1 "Could not create fee rate from %s btc per KB"
                                            (btcPerKiloByteForFastTrans.ToString()), ex)
 
-        let destination = 
+        let finalDestination = 
             if SilentPaymentAddress.IsSilentPaymentAddress destination then
                 // calculate bogus silent payment destinantion using throwaway private key,
                 // as it will only be used for fee estimation
@@ -438,7 +431,7 @@ module Account =
 
         let transactionBuilder = CreateTransactionAndCoinsToBeSigned account
                                                                      initiallyUsedInputs
-                                                                     destination
+                                                                     finalDestination
                                                                      amount
 
         try
@@ -486,13 +479,13 @@ module Account =
 
         let isSilentPayment = SilentPaymentAddress.IsSilentPaymentAddress destination
 
-        let destination =
+        let finalDestination =
             if isSilentPayment then
                 CalculateSilentPaymentDestination account txMetadata.Inputs destination privateKey
             else
                 destination
 
-        let finalTransactionBuilder = CreateTransactionAndCoinsToBeSigned account txMetadata.Inputs destination amount
+        let finalTransactionBuilder = CreateTransactionAndCoinsToBeSigned account txMetadata.Inputs finalDestination amount
 
         finalTransactionBuilder.AddKeys privateKey |> ignore
         finalTransactionBuilder.SendFees (Money.Satoshis btcMinerFee.EstimatedFeeInSatoshis)
@@ -725,8 +718,9 @@ module Account =
                 // (FIXME: this is only valid for the first version of segwit, fix it!)
                 Fixed [ 42u; 62u ]
             | Currency.BTC, _ when SilentPaymentAddress.IsSilentPaymentAddress address ->
-                // https://github.com/bitcoin/bips/blob/master/bip-0352.mediawiki#address-encoding
-                Variable { Minimum = 116u; Maximum = 1023u }
+                Variable 
+                    { Minimum = SilentPaymentAddress.MinimumEncodedLength
+                      Maximum = SilentPaymentAddress.MaximumEncodedLength }
             | Currency.LTC, _ when address.StartsWith LITECOIN_ADDRESS_BECH32_PREFIX ->
                 // taken from https://coin.space/all-about-address-types/, e.g. ltc1q3qkpj5s4ru3cx9t7dt27pdfmz5aqy3wplamkns
                 // FIXME: hopefully someone replies/documents https://bitcoin.stackexchange.com/questions/110975/how-long-can-bech32-addresses-be-in-the-litecoin-mainnet