[6.0.0] Header.checkPow method

.gitignore

@@ -11,6 +11,7 @@
 
 yarn.lock
 *.log
+yarn.lock
 docs/spec/out/
 test-out/
 flamegraphs/

core/shared/src/main/scala/sigma/SigmaDsl.scala

@@ -471,6 +471,11 @@ trait Header {
     */
   def serializeWithoutPoW: Coll[Byte]
 
+  /**
+    * @return result of header's proof-of-work validation
+    */
+  def checkPow: Boolean
+
 }
 
 /** Runtime representation of Context ErgoTree type.

core/shared/src/main/scala/sigma/reflection/ReflectionData.scala

@@ -346,6 +346,9 @@ object ReflectionData {
         },
         mkMethod(clazz, "powDistance", Array[Class[_]]()) { (obj, _) =>
           obj.asInstanceOf[Header].powDistance
+        },
+        mkMethod(clazz, "checkPow", Array[Class[_]]()) { (obj, _) =>
+          obj.asInstanceOf[Header].checkPow
         }
       )
     )

core/shared/src/main/scala/sigma/util/NBitsUtils.scala

@@ -0,0 +1,84 @@
+package sigma.util
+
+import java.math.BigInteger
+
+object NBitsUtils {
+
+  /**
+    * <p>The "compact" format is a representation of a whole number N using an unsigned 32 bit number similar to a
+    * floating point format. The most significant 8 bits are the unsigned exponent of base 256. This exponent can
+    * be thought of as "number of bytes of N". The lower 23 bits are the mantissa. Bit number 24 (0x800000) represents
+    * the sign of N. Therefore, N = (-1^sign) * mantissa * 256^(exponent-3).</p>
+    *
+    * <p>Satoshi's original implementation used BN_bn2mpi() and BN_mpi2bn(). MPI uses the most significant bit of the
+    * first byte as sign. Thus 0x1234560000 is compact 0x05123456 and 0xc0de000000 is compact 0x0600c0de. Compact
+    * 0x05c0de00 would be -0x40de000000.</p>
+    *
+    * <p>Bitcoin only uses this "compact" format for encoding difficulty targets, which are unsigned 256bit quantities.
+    * Thus, all the complexities of the sign bit and using base 256 are probably an implementation accident.</p>
+    */
+  def decodeCompactBits(compact: Long): BigInt = {
+    val size: Int = (compact >> 24).toInt & 0xFF
+    val bytes: Array[Byte] = new Array[Byte](4 + size)
+    bytes(3) = size.toByte
+    if (size >= 1) bytes(4) = ((compact >> 16) & 0xFF).toByte
+    if (size >= 2) bytes(5) = ((compact >> 8) & 0xFF).toByte
+    if (size >= 3) bytes(6) = (compact & 0xFF).toByte
+    decodeMPI(bytes)
+  }
+
+  /**
+    * @see Utils#decodeCompactBits(long)
+    */
+  def encodeCompactBits(requiredDifficulty: BigInt): Long = {
+    val value = requiredDifficulty.bigInteger
+    var result: Long = 0L
+    var size: Int = value.toByteArray.length
+    if (size <= 3) {
+      result = value.longValue << 8 * (3 - size)
+    } else {
+      result = value.shiftRight(8 * (size - 3)).longValue
+    }
+    // The 0x00800000 bit denotes the sign.
+    // Thus, if it is already set, divide the mantissa by 256 and increase the exponent.
+    if ((result & 0x00800000L) != 0) {
+      result >>= 8
+      size += 1
+    }
+    result |= size << 24
+    val a: Int = if (value.signum == -1) 0x00800000 else 0
+    result |= a
+    result
+  }
+
+
+  /** Parse 4 bytes from the byte array (starting at the offset) as unsigned 32-bit integer in big endian format. */
+  def readUint32BE(bytes: Array[Byte]): Long = ((bytes(0) & 0xffL) << 24) | ((bytes(1) & 0xffL) << 16) | ((bytes(2) & 0xffL) << 8) | (bytes(3) & 0xffL)
+
+  /**
+    * MPI encoded numbers are produced by the OpenSSL BN_bn2mpi function. They consist of
+    * a 4 byte big endian length field, followed by the stated number of bytes representing
+    * the number in big endian format (with a sign bit).
+    *
+    */
+  private def decodeMPI(mpi: Array[Byte]): BigInteger = {
+
+    val length: Int = readUint32BE(mpi).toInt
+    val buf = new Array[Byte](length)
+    System.arraycopy(mpi, 4, buf, 0, length)
+
+    if (buf.length == 0) {
+      BigInteger.ZERO
+    } else {
+      val isNegative: Boolean = (buf(0) & 0x80) == 0x80
+      if (isNegative) buf(0) = (buf(0) & 0x7f).toByte
+      val result: BigInteger = new BigInteger(buf)
+      if (isNegative) {
+        result.negate
+      } else {
+        result
+      }
+    }
+  }
+
+}

data/shared/src/main/scala/org/ergoplatform/HeaderWithoutPow.scala

@@ -23,6 +23,12 @@ class HeaderWithoutPow(val version:  Byte, // 1 byte
   def toHeader(powSolution: AutolykosSolution, bytes: Array[Byte]): ErgoHeader =
     ErgoHeader(version, parentId, ADProofsRoot, stateRoot, transactionsRoot, timestamp,
       nBits, height, extensionRoot, powSolution, votes, unparsedBytes, bytes)
+
+  override def toString: String = {
+    s"HeaderWithoutPow($version, $parentId, ${bytesToId(ADProofsRoot)}, ${bytesToId(stateRoot)}, " +
+      s"${bytesToId(transactionsRoot)}, $timestamp, $nBits, $height, ${bytesToId(extensionRoot)}, ${bytesToId(votes)}, " +
+      s"${bytesToId(unparsedBytes)} )"
+  }
 }
 
 object HeaderWithoutPow {

data/shared/src/main/scala/sigma/ast/methods.scala

@@ -1456,11 +1456,27 @@ case object SHeaderMethods extends MonoTypeMethods {
   lazy val powDistanceMethod      = propertyCall("powDistance", SBigInt, 14, FixedCost(JitCost(10)))
   lazy val votesMethod            = propertyCall("votes", SByteArray, 15, FixedCost(JitCost(10)))
 
-  protected override def getMethods() = super.getMethods() ++ Seq(
+  // cost of checkPoW is 700 as about 2*32 hashes required, and 1 hash (id) over short data costs 10
+  lazy val checkPowMethod = SMethod(
+    this, "checkPow", SFunc(Array(SHeader), SBoolean), 16, FixedCost(JitCost(700)))
+    .withIRInfo(MethodCallIrBuilder)
+    .withInfo(MethodCall, "Validate header's proof-of-work")
+
+  private lazy val v5Methods = super.getMethods() ++ Seq(
     idMethod, versionMethod, parentIdMethod, ADProofsRootMethod, stateRootMethod, transactionsRootMethod,
     timestampMethod, nBitsMethod, heightMethod, extensionRootMethod, minerPkMethod, powOnetimePkMethod,
-    powNonceMethod, powDistanceMethod, votesMethod
-  )
+    powNonceMethod, powDistanceMethod, votesMethod)
+
+  // 6.0 : checkPow method added
+  private lazy val v6Methods = v5Methods ++ Seq(checkPowMethod)
+
+  protected override def getMethods() = {
+    if (VersionContext.current.isV6SoftForkActivated) {
+      v6Methods
+    } else {
+      v5Methods
+    }
+  }
 }
 
 /** Type descriptor of `PreHeader` type of ErgoTree. */

data/shared/src/main/scala/sigma/data/CHeader.scala

@@ -4,6 +4,7 @@ import org.ergoplatform.{AutolykosSolution, ErgoHeader, HeaderWithoutPow, Header
 import scorex.crypto.authds.ADDigest
 import scorex.crypto.hash.Digest32
 import scorex.util.{bytesToId, idToBytes}
+import sigma.pow.Autolykos2PowValidation
 import sigma.{AvlTree, BigInt, Coll, Colls, GroupElement, Header}
 
 /** A default implementation of [[Header]] interface.
@@ -66,10 +67,11 @@ class CHeader(val ergoHeader: ErgoHeader) extends Header with WrapperOf[ErgoHead
   override def wrappedValue: ErgoHeader = ergoHeader
 
   override def serializeWithoutPoW: Coll[Byte] = {
-    val headerWithoutPow = HeaderWithoutPow(version, bytesToId(parentId.toArray), Digest32 @@ ADProofsRoot.toArray,
-      ADDigest @@ stateRoot.digest.toArray, Digest32 @@ transactionsRoot.toArray, timestamp,
-      nBits, height, Digest32 @@ extensionRoot.toArray, votes.toArray, unparsedBytes.toArray)
-    Colls.fromArray(HeaderWithoutPowSerializer.toBytes(headerWithoutPow))
+    Colls.fromArray(HeaderWithoutPowSerializer.toBytes(ergoHeader))
+  }
+
+  override def checkPow: Boolean = {
+    Autolykos2PowValidation.checkPoWForVersion2(this)
   }
 
   override def toString: String =

data/shared/src/main/scala/sigma/eval/ErgoTreeEvaluator.scala

@@ -1,6 +1,6 @@
 package sigma.eval
 
-import sigma.{AvlTree, Coll, Context}
+import sigma.{AvlTree, Coll, Context, Header}
 import sigma.ast.{Constant, FixedCost, MethodCall, OperationCostInfo, OperationDesc, PerItemCost, SType, TypeBasedCost}
 import sigma.data.KeyValueColl
 

data/shared/src/main/scala/sigma/pow/Autolykos2PowValidation.scala

@@ -0,0 +1,176 @@
+package sigma.pow
+
+
+import scorex.crypto.hash.Blake2b256
+import scorex.utils.{Bytes, Ints, Longs}
+import sigma.Header
+import sigma.crypto.{BcDlogGroup, BigIntegers, CryptoConstants}
+import sigma.util.NBitsUtils
+
+/**
+  * Functions used to validate Autolykos2 Proof-of-Work.
+  */
+object Autolykos2PowValidation {
+
+  type Height = Int
+
+  /**
+    * k value for k-sum problem Autolykos is based on (find k numbers in table on N size)
+    */
+  private val k = 32
+
+  /**
+    * Initial size of N  value for k-sum problem Autolykos is based on (find k numbers in table on N size).
+    * It grows from it since predefined block height in Autolykos 2.
+    */
+  private val NStart = 26
+
+  /**
+    * Group order, used in Autolykos V.1 for non-outsourceability,
+    * and also to obtain target in both Autolykos v1 and v2
+    */
+  private val q: BigInt = CryptoConstants.dlogGroup.order
+
+  /**
+    * Number of elements in a table to find k-sum problem solution on top of
+    */
+  val NBase: Int = Math.pow(2, NStart.toDouble).toInt
+
+  /**
+    * Initial height since which table (`N` value) starting to increase by 5% per `IncreasePeriodForN` blocks
+    */
+  val IncreaseStart: Height = 600 * 1024
+
+  /**
+    * Table size (`N`) increased every 50 * 1024 blocks
+    */
+  val IncreasePeriodForN: Height = 50 * 1024
+
+  /**
+    * On this height, the table (`N` value) will stop to grow.
+    * Max N on and after this height would be 2,143,944,600 which is still less than 2^^31.
+    */
+  val NIncreasementHeightMax: Height = 4198400
+
+  /**
+    * Blake2b256 hash function invocation
+    * @param in - input bit-string
+    * @return - 256 bits (32 bytes) array
+    */
+  def hash(in: Array[Byte]): Array[Byte] = Blake2b256.hash(in)
+
+  /**
+    * Convert byte array to unsigned integer
+    * @param in - byte array
+    * @return - unsigned integer
+    */
+  def toBigInt(in: Array[Byte]): BigInt = BigInt(BigIntegers.fromUnsignedByteArray(in))
+
+  /**
+    * Constant data to be added to hash function to increase its calculation time
+    */
+  val M: Array[Byte] = (0 until 1024).toArray.flatMap(i => Longs.toByteArray(i.toLong))
+
+  /**
+    * Calculates table size (N value) for a given height (moment of time)
+    *
+    * @see papers/yellow/pow/ErgoPow.tex for full description and test vectors
+    * @param headerHeight - height of a header to mine
+    * @return - N value
+    */
+  def calcN(headerHeight: Height): Int = {
+    val height = Math.min(NIncreasementHeightMax, headerHeight)
+    if (height < IncreaseStart) {
+      NBase
+    } else {
+      val itersNumber = (height - IncreaseStart) / IncreasePeriodForN + 1
+      (1 to itersNumber).foldLeft(NBase) { case (step, _) =>
+        step / 100 * 105
+      }
+    }
+  }
+
+  def calcN(header: Header): Int = calcN(header.height)
+
+  /**
+    * Hash function that takes `m` and `nonceBytes` and returns a list of size `k` with numbers in
+    * [0,`N`)
+    */
+  private def genIndexes(k: Int, seed: Array[Byte], N: Int): Seq[Int] = {
+    val hash = Blake2b256(seed)
+    val extendedHash = Bytes.concat(hash, hash.take(3))
+    (0 until k).map { i =>
+      BigInt(1, extendedHash.slice(i, i + 4)).mod(N).toInt
+    }
+  }.ensuring(_.length == k)
+
+  /**
+    * Generate element of Autolykos equation.
+    */
+  private def genElementV2(indexBytes: Array[Byte], heightBytes: => Array[Byte]): BigInt = {
+    // Autolykos v. 2: H(j|h|M) (line 5 from the Algo 2 of the spec)
+    toBigInt(hash(Bytes.concat(indexBytes, heightBytes, M)).drop(1))
+  }
+
+  def hitForVersion2ForMessage(k: Int, msg: Array[Byte], nonce: Array[Byte], h: Array[Byte], N: Int): BigInt = {
+
+    val prei8 = BigIntegers.fromUnsignedByteArray(hash(Bytes.concat(msg, nonce)).takeRight(8))
+    val i = BigIntegers.asUnsignedByteArray(4, prei8.mod(BigInt(N).underlying()))
+    val f = Blake2b256(Bytes.concat(i, h, M)).drop(1) // .drop(1) is the same as takeRight(31)
+    val seed = Bytes.concat(f, msg, nonce) // Autolykos v1, Alg. 2, line4:
+
+    val indexes = genIndexes(k, seed, N)
+    //pk and w not used in v2
+    val elems = indexes.map(idx => genElementV2(Ints.toByteArray(idx), h))
+    val f2 = elems.sum
+
+    // sum as byte array is always about 32 bytes
+    val array: Array[Byte] = BigIntegers.asUnsignedByteArray(32, f2.underlying())
+    val ha = hash(array)
+    toBigInt(ha)
+  }
+
+  /**
+    * Header digest ("message" for default GPU miners) a miner is working on
+    */
+  def msgByHeader(h: Header): Array[Byte] = Blake2b256(h.serializeWithoutPoW.toArray)
+
+  /**
+    * Get hit for Autolykos v2 header (to test it then against PoW target)
+    *
+    * @param header - header to check PoW for
+    * @return PoW hit
+    */
+  def hitForVersion2(header: Header): BigInt = {
+
+    val msg = msgByHeader(header)
+    val nonce = header.powNonce
+
+    val h = Ints.toByteArray(header.height)  // used in AL v.2 only
+
+    val N = calcN(header)
+
+    hitForVersion2ForMessage(k, msg, nonce.toArray, h, N)
+  }
+
+  /**
+    * Get target `b` from encoded difficulty `nBits`
+    */
+  def getB(nBits: Long): BigInt = {
+    q / NBitsUtils.decodeCompactBits(nBits)
+  }
+
+  /**
+    * Check PoW for Autolykos v2 header
+    *
+    * @param header - header to check PoW for
+    * @return whether PoW is valid or not
+    */
+  def checkPoWForVersion2(header: Header): Boolean = {
+    val b = getB(header.nBits)
+    // for version 2, we're calculating hit and compare it with target
+    val hit = hitForVersion2(header)
+    hit < b
+  }
+
+}

docs/LangSpec.md

@@ -249,6 +249,10 @@ class Context {
 
 /** Represents data of the block headers available in scripts. */
 class Header {  
+
+  /** Validate header's proof-of-work */  
+  def checkPow: Boolean
+
   /** Bytes representation of ModifierId of this Header */
   def id: Coll[Byte]