From 3e0d21d197dc822323276d3b448975e6d06ed84c Mon Sep 17 00:00:00 2001
From: Dima <somedayofmylife@gmail.com>
Date: Wed, 22 Aug 2018 11:26:10 +0300
Subject: [PATCH] Ecdsa recreate pair from secret (#2)

* add possibility to re-create public key from private key for ECDSA alghorithm

* change version

* change version

* add comments, change version of cats-effect

* add comments, change method name

* change comment

* typo
---
 build.sbt                                     | 12 ++++-----
 .../scala/fluence/crypto/ecdsa/Ecdsa.scala    | 26 +++++++++++++++++++
 .../scala/fluence/crypto/SignatureSpec.scala  | 14 +++++++++-
 project/build.properties                      |  2 +-
 4 files changed, 46 insertions(+), 8 deletions(-)

diff --git a/build.sbt b/build.sbt
index 7d99411..ecd6a52 100644
--- a/build.sbt
+++ b/build.sbt
@@ -14,7 +14,7 @@ val scalaV = scalaVersion := "2.12.5"
 
 val commons = Seq(
   scalaV,
-  version                   := "0.0.1",
+  version                   := "0.0.2",
   fork in Test              := true,
   parallelExecution in Test := false,
   organization              := "one.fluence",
@@ -33,13 +33,13 @@ commons
 
 val CodecV = "0.0.3"
 
-val CatsEffectV = "1.0.0-RC"
+val CatsEffectV = "1.0.0-RC3"
 
 val SloggingV = "0.6.1"
 
 val ScalatestV = "3.0.+"
 
-val bouncyCastle = "org.bouncycastle"            % "bcprov-jdk15on"        % "1.59"
+val bouncyCastle = "org.bouncycastle" % "bcprov-jdk15on" % "1.59"
 
 enablePlugins(AutomateHeaderPlugin)
 
@@ -158,12 +158,12 @@ lazy val `crypto-jwt` = crossProject(JVMPlatform, JSPlatform)
   .settings(
     commons,
     libraryDependencies ++= Seq(
-      "one.fluence" %%% "codec-circe" % CodecV,
-      "org.scalatest" %%% "scalatest" % ScalatestV % Test
+      "one.fluence"   %%% "codec-circe" % CodecV,
+      "org.scalatest" %%% "scalatest"   % ScalatestV % Test
     )
   )
   .jsSettings(
-    fork in Test := false,
+    fork in Test      := false,
     scalaJSModuleKind := ModuleKind.CommonJSModule
   )
   .enablePlugins(AutomateHeaderPlugin)
diff --git a/hashsign/jvm/src/main/scala/fluence/crypto/ecdsa/Ecdsa.scala b/hashsign/jvm/src/main/scala/fluence/crypto/ecdsa/Ecdsa.scala
index 9f991b0..91a436f 100644
--- a/hashsign/jvm/src/main/scala/fluence/crypto/ecdsa/Ecdsa.scala
+++ b/hashsign/jvm/src/main/scala/fluence/crypto/ecdsa/Ecdsa.scala
@@ -23,6 +23,7 @@ import java.security.interfaces.ECPrivateKey
 
 import cats.Monad
 import cats.data.EitherT
+import fluence.crypto.KeyPair.Secret
 import fluence.crypto.{KeyPair, _}
 import fluence.crypto.hash.JdkCryptoHasher
 import fluence.crypto.signature.{SignAlgo, SignatureChecker, Signer}
@@ -72,6 +73,31 @@ class Ecdsa(curveType: String, scheme: String, hasher: Option[Crypto.Hasher[Arra
         } yield keyPair
     }
 
+  /**
+    * Restores pair of keys from the known secret key.
+    * The public key will be the same each method call with the same secret key.
+    * @param sk secret key
+    * @return key pair
+    */
+  def restorePairFromSecret[F[_]: Monad](sk: Secret): EitherT[F, CryptoError, KeyPair] =
+    for {
+      ecSpec ← EitherT.fromOption(
+        Option(ECNamedCurveTable.getParameterSpec(curveType)),
+        CryptoError("Parameter spec for the curve is not available.")
+      )
+      keyPair ← nonFatalHandling {
+        val hex = sk.value.toHex
+        val d = new BigInteger(hex, HEXradix)
+        // to re-create public key from private we need to multiply known from curve point G with D (private key)
+        // result will be point Q (public key)
+        // https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm
+        val g = ecSpec.getG
+        val q = g.multiply(d)
+        val pk = ByteVector(q.getEncoded(true))
+        KeyPair.fromByteVectors(pk, sk.value)
+      }("Could not generate KeyPair from private key. Unexpected.")
+    } yield keyPair
+
   def sign[F[_]: Monad](
     keyPair: KeyPair,
     message: ByteVector
diff --git a/hashsign/jvm/src/test/scala/fluence/crypto/SignatureSpec.scala b/hashsign/jvm/src/test/scala/fluence/crypto/SignatureSpec.scala
index 52e5b0a..f4bcbfd 100644
--- a/hashsign/jvm/src/test/scala/fluence/crypto/SignatureSpec.scala
+++ b/hashsign/jvm/src/test/scala/fluence/crypto/SignatureSpec.scala
@@ -18,6 +18,7 @@
 package fluence.crypto
 
 import java.io.File
+import java.math.BigInteger
 
 import cats.data.EitherT
 import cats.instances.try_._
@@ -31,7 +32,7 @@ import scala.util.{Random, Try}
 
 class SignatureSpec extends WordSpec with Matchers {
 
-  def rndBytes(size: Int) = Random.nextString(10).getBytes
+  def rndBytes(size: Int): Array[Byte] = Random.nextString(10).getBytes
 
   def rndByteVector(size: Int) = ByteVector(rndBytes(size))
 
@@ -125,5 +126,16 @@ class SignatureSpec extends WordSpec with Matchers {
       //try to store key into previously created file
       storage.storeKeyPair(keys).attempt.unsafeRunSync().isLeft shouldBe true
     }
+
+    "restore key pair from secret key" in {
+      val algo = Ecdsa.signAlgo
+      val testKeys = algo.generateKeyPair.unsafe(None)
+
+      val ecdsa = Ecdsa.ecdsa_secp256k1_sha256
+
+      val newKeys = ecdsa.restorePairFromSecret(testKeys.secretKey).extract
+
+      testKeys shouldBe newKeys
+    }
   }
 }
diff --git a/project/build.properties b/project/build.properties
index 90e7013..2daea37 100644
--- a/project/build.properties
+++ b/project/build.properties
@@ -1 +1 @@
-sbt.version = 1.1.4
+sbt.version = 1.2.1