2019 12 17 sign ext key (#959)

* Create ExtSign, use it on ExtPrivateKey

* Add documentation on how to Sign things with ExtSign

* Add ExtSign.sign for a bip32 path

* Make sign(bytes,path) not return a Future, add documentation

* Address nadav's code review

* Fix mdoc sign.md

core-test/src/test/scala/org/bitcoins/core/crypto/ExtKeySpec.scala

@@ -3,25 +3,25 @@ package org.bitcoins.core.crypto
 import org.bitcoins.testkit.core.gen.CryptoGenerators
 import org.bitcoins.core.number.UInt32
 import org.bitcoins.core.util.BitcoinSLogger
+import org.bitcoins.testkit.util.BitcoinSUnitTest
 import org.scalacheck.{Gen, Prop, Properties}
 
 import scala.util.Success
 
-class ExtKeySpec extends Properties("ExtKeySpec") {
-  private val logger = BitcoinSLogger.logger
-  property("serialization symmetry") = {
+class ExtKeySpec extends BitcoinSUnitTest {
+  private val nonHardened: Gen[UInt32] =
+    Gen.choose(0L, ((1L << 31) - 1)).map(UInt32(_))
+  private val hardened: Gen[UInt32] =
+    Gen.choose(1L << 31, (1L << 32) - 1).map(UInt32(_))
+
+  it must "have serialization symmetry" in {
     Prop.forAll(CryptoGenerators.extKey) { extKey =>
       ExtKey.fromString(extKey.toString) == Success(extKey) &&
         ExtKey(extKey.bytes) == extKey
     }
   }
 
-  private def nonHardened: Gen[UInt32] =
-    Gen.choose(0L, ((1L << 31) - 1)).map(UInt32(_))
-  private def hardened: Gen[UInt32] =
-    Gen.choose(1L << 31, (1L << 32) - 1).map(UInt32(_))
-
-  property("derivation identity 1") = {
+  it must "have derivation identity 1" in {
     Prop.forAllNoShrink(CryptoGenerators.extPrivateKey,
       nonHardened,
       nonHardened,
@@ -57,7 +57,7 @@ class ExtKeySpec extends Properties("ExtKeySpec") {
     }
   }
 
-  property("derivation identity 2") = {
+  it must "derivation identity 2" in {
     Prop.forAllNoShrink(CryptoGenerators.extPrivateKey,
       hardened,
       nonHardened,

core-test/src/test/scala/org/bitcoins/core/crypto/ExtSignTest.scala

@@ -0,0 +1,27 @@
+package org.bitcoins.core.crypto
+
+import org.bitcoins.testkit.core.gen.{CryptoGenerators, HDGenerators}
+import org.bitcoins.testkit.util.{BitcoinSAsyncTest, BitcoinSUnitTest}
+
+class ExtSignTest extends BitcoinSAsyncTest {
+
+  it must "be able to sign something that extends ExtSignKey" in {
+    forAll(CryptoGenerators.extPrivateKey, CryptoGenerators.sha256Digest) {
+      case (extPrivKey, hash) =>
+        val sig = extPrivKey.sign(hash.bytes)
+        assert(extPrivKey.publicKey.verify(hash,sig))
+    }
+  }
+
+  it must "be able to sign a specific path of a ext key" in {
+    forAllAsync(CryptoGenerators.extPrivateKey, CryptoGenerators.sha256Digest, HDGenerators.bip32Path) {
+      case (extPrivKey, hash, path) =>
+        val sigF = extPrivKey.deriveAndSignFuture(hash.bytes,path)
+        val childPubKey = extPrivKey.deriveChildPubKey(path).get
+        sigF.map { sig =>
+          assert(childPubKey.key.verify(hash,sig))
+        }
+
+    }
+  }
+}

core-test/src/test/scala/org/bitcoins/core/crypto/SignTest.scala

@@ -29,8 +29,6 @@ class SignTest extends BitcoinSUnitTest {
         val sigF = signTestImpl.signFunction(hash.bytes)
 
         sigF.map(sig => assert(pubKey.verify(hash.hex, sig)))
-
     }
   }
-
 }

core/src/main/scala/org/bitcoins/core/crypto/ExtKey.scala

@@ -5,10 +5,10 @@ import org.bitcoins.core.hd.{BIP32Node, BIP32Path}
 import org.bitcoins.core.number.{UInt32, UInt8}
 import org.bitcoins.core.protocol.NetworkElement
 import org.bitcoins.core.util._
-import scodec.bits.ByteVector
-import scodec.bits.HexStringSyntax
+import scodec.bits.{ByteVector, HexStringSyntax}
 
 import scala.annotation.tailrec
+import scala.concurrent.Future
 import scala.util.{Failure, Success, Try}
 
 /**
@@ -157,7 +157,7 @@ object ExtKey extends Factory[ExtKey] {
   }
 }
 
-sealed abstract class ExtPrivateKey extends ExtKey {
+sealed abstract class ExtPrivateKey extends ExtKey with ExtSign {
   import ExtKeyVersion._
 
   override protected type VersionType = ExtKeyPrivVersion
@@ -210,6 +210,20 @@ sealed abstract class ExtPrivateKey extends ExtKey {
   def deriveChildPrivKey(idx: Long): Try[ExtPrivateKey] = {
     Try(UInt32(idx)).map(deriveChildPrivKey)
   }
+
+  override def publicKey: ECPublicKey = key.publicKey
+
+  override def signFunction: ByteVector => Future[ECDigitalSignature] = {
+    key.signFunction
+  }
+
+  /** Signs the given bytes with the given [[BIP32Path path]] */
+  override def deriveAndSignFuture: (
+      ByteVector,
+      BIP32Path) => Future[ECDigitalSignature] = {
+    case (bytes, path) =>
+      deriveChildPrivKey(path).signFunction(bytes)
+  }
 }
 
 object ExtPrivateKey extends Factory[ExtPrivateKey] {

core/src/main/scala/org/bitcoins/core/crypto/Sign.scala

@@ -1,5 +1,6 @@
 package org.bitcoins.core.crypto
 
+import org.bitcoins.core.hd.BIP32Path
 import scodec.bits.ByteVector
 
 import scala.concurrent.duration.DurationInt
@@ -58,3 +59,14 @@ object Sign {
     }, publicKey)
   }
 }
+
+/** A signing interface for [[ExtKey]] */
+trait ExtSign extends Sign {
+
+  def deriveAndSignFuture: (ByteVector, BIP32Path) => Future[ECDigitalSignature]
+
+  /** First derives the child key that corresponds to [[BIP32Path path]] and then signs */
+  def sign(bytes: ByteVector, path: BIP32Path): ECDigitalSignature = {
+    Await.result(deriveAndSignFuture(bytes, path), 30.seconds)
+  }
+}

docs/core/core-intro.md

@@ -65,39 +65,6 @@ After providing this information, you can generate a validly signed bitcoin tran
 
 To see a complete example of this, see [our `TxBuilder` example](txbuilder.md)
 
-### The [`Sign` API](/api/org/bitcoins/core/crypto/Sign)
-
-This is the API we define to sign things with. It takes in an arbitrary byte vector and returns a `Future[ECDigitalSignature]`. The reason we incorporate `Future`s here is for extensibility of this API. We would like to provide implementations of this API for hardware devices, which need to be asynchrnous since they may require user input.
-
-From [`core/src/main/scala/org/bitcoins/core/crypto/Sign.scala`](/api/org/bitcoins/core/crypto/Sign):
-
-```scala mdoc
-import scodec.bits._
-import org.bitcoins.core.crypto._
-import scala.concurrent._
-import scala.concurrent.duration._
-
-trait Sign {
-  def signFunction: ByteVector => Future[ECDigitalSignature]
-
-  def signFuture(bytes: ByteVector): Future[ECDigitalSignature] =
-    signFunction(bytes)
-
-  def sign(bytes: ByteVector): ECDigitalSignature = {
-    Await.result(signFuture(bytes), 30.seconds)
-  }
-
-  def publicKey: ECPublicKey
-}
-
-```
-
-The `ByteVector` that is input to the `signFunction` should be the hash that is output from [`TransactionSignatureSerializer`](/api/org/bitcoins/core/crypto/TransactionSignatureSerializer)'s `hashForSignature` method. Our in-memory [`ECKey`](/api/org/bitcoins/core/crypto/ECKey) types implement the `Sign` API.
-
-If you wanted to implement a new `Sign` api for a hardware wallet, you can easily pass it into the `TxBuilder`/`Signer` classes to allow for you to use those devices to sign with Bitcoin-S.
-
-This API is currently used to sign ordinary transactions with our [`Signer`](/api/org/bitcoins/core/wallet/signer/Signer)s. The `Signer` subtypes (i.e. `P2PKHSigner`) implement the specific functionality needed to produce a valid digital signature for their corresponding script type.
-
 ### Verifying a transaction's script is valid (does not check if UTXO is valid)
 
 Transactions are run through the interpreter to check their validity. These are packaged up into an object called `ScriptProgram`, which contains the following:

docs/core/hd-keys.md

@@ -127,3 +127,7 @@ firstAccountAddress.value
 // HD path to generate an address at:
 val nextAddressPath: SegWitHDPath = firstAddressPath.next
 ```
+
+### Signing things with HD keys
+
+Please see [sign.md](sign.md) for information on how to sign things with HD keys.

docs/core/sign.md

@@ -0,0 +1,61 @@
+---
+id: sign
+title: Sign api
+---
+
+### The [`Sign` API](org/bitcoins/core/crypto/Sign.scala)
+
+This is the API we define to sign things with. It takes in an arbitrary byte vector and returns a `Future[ECDigitalSignature]`. The reason we incorporate `Future`s here is for extensibility of this API. We would like to provide implementations of this API for hardware devices, which need to be asynchrnous since they may require user input.
+
+From [Sign.scala](../../core/src/main/scala/org/bitcoins/core/crypto/Sign.scala):
+
+```scala mdoc
+import scodec.bits._
+import org.bitcoins.core.crypto._
+import scala.concurrent._
+import scala.concurrent.duration._
+
+trait Sign {
+  def signFunction: ByteVector => Future[ECDigitalSignature]
+
+  def signFuture(bytes: ByteVector): Future[ECDigitalSignature] =
+    signFunction(bytes)
+
+  def sign(bytes: ByteVector): ECDigitalSignature = {
+    Await.result(signFuture(bytes), 30.seconds)
+  }
+
+  def publicKey: ECPublicKey
+}
+
+```
+
+The `ByteVector` that is input to the `signFunction` should be the hash that is output from [`TransactionSignatureSerializer`](/api/org/bitcoins/core/crypto/TransactionSignatureSerializer)'s `hashForSignature` method. Our in-memory [`ECKey`](/api/org/bitcoins/core/crypto/ECKey) types implement the `Sign` API.
+
+If you wanted to implement a new `Sign` api for a hardware wallet, you can easily pass it into the `TxBuilder`/`Signer` classes to allow for you to use those devices to sign with Bitcoin-S.
+
+This API is currently used to sign ordinary transactions with our [`Signer`](/api/org/bitcoins/core/wallet/signer/Signer)s. The `Signer` subtypes (i.e. `P2PKHSigner`) implement the specific functionality needed to produce a valid digital signature for their corresponding script type.
+
+
+### The [`ExtSign`](../../core/src/main/scala/org/bitcoins/core/crypto/Sign.scala) API.
+
+An [ExtKey](org/bitcoins/core/crypto/ExtKey.scala) is a data structure that can be used to generate more keys from a parent key. For more information look at [hd-keys.md](hd-keys.md)
+
+You can sign with `ExtPrivateKey` the same way you could with a normal `ECPrivateKey`.
+
+```scala mdoc:to-string
+import org.bitcoins.core.hd._
+import org.bitcoins.core.crypto._
+
+val extPrivKey = ExtPrivateKey(ExtKeyVersion.SegWitMainNetPriv)
+
+extPrivKey.sign(DoubleSha256Digest.empty.bytes)
+
+val path = BIP32Path(Vector(BIP32Node(0,false)))
+
+extPrivKey.sign(DoubleSha256Digest.empty.bytes,path)
+```
+
+With `ExtSign`, you can use `ExtPrivateKey` to sign transactions inside of `TxBuilder` since `UTXOSpendingInfo` takes in `Sign` as a parameter. 
+
+You can also provide a `path` to use to derive a child `ExtPrivateKey`, and then sign with that child private key

website/sidebars.json

@@ -5,6 +5,7 @@
       "core/core-intro",
       "core/addresses",
       "core/hd-keys",
+      "core/sign",
       "core/txbuilder"
     ],
     "RPC clients": [