Add missing CryptoFacade methods

interpreter/src/main/scala/sigmastate/crypto/CryptoContext.scala

@@ -2,8 +2,11 @@ package sigmastate.crypto
 
 import java.math.BigInteger
 
-/** A context for cryptographic operations. */
+/** A context for cryptographic operations over elliptic curve group. */
 abstract class CryptoContext {
+  /** The underlying elliptic curve descriptor. */
+  def curve: Curve
+
   /** The characteristics of the underlying finite field. */
   def fieldCharacteristic: BigInteger
 

interpreter/src/main/scala/sigmastate/crypto/CryptoContextJvm.scala

@@ -6,9 +6,11 @@ import java.math.BigInteger
 
 /** JVM implementation of context for cryptographic operations using Bouncycastle. */
 class CryptoContextJvm(x9params: X9ECParameters) extends CryptoContext {
-  private lazy val curve = x9params.getCurve
+  private lazy val _curve = x9params.getCurve
 
-  override def fieldCharacteristic: BigInteger = curve.getField.getCharacteristic
+  override def curve: Curve = Platform.Curve(_curve)
+
+  override def fieldCharacteristic: BigInteger = _curve.getField.getCharacteristic
 
   override def order: BigInteger = x9params.getN
 
@@ -17,14 +19,14 @@ class CryptoContextJvm(x9params: X9ECParameters) extends CryptoContext {
   }
 
   override def validatePoint(x: BigInteger, y: BigInteger): Ecp = {
-    Platform.Ecp(curve.validatePoint(x, y))
+    Platform.Ecp(_curve.validatePoint(x, y))
   }
 
   override def infinity(): Ecp = {
-    Platform.Ecp(curve.getInfinity)
+    Platform.Ecp(_curve.getInfinity)
   }
 
   override def decodePoint(encoded: Array[Byte]): Ecp = {
-    Platform.Ecp(curve.decodePoint(encoded))
+    Platform.Ecp(_curve.decodePoint(encoded))
   }
 }

interpreter/src/main/scala/sigmastate/crypto/CryptoFacade.scala

@@ -48,6 +48,19 @@ object CryptoFacade {
   /** Returns byte representation of the given field element. */
   def encodeFieldElem(p: ECFieldElem): Array[Byte] = Platform.encodeFieldElem(p)
 
+  /** Byte representation of the given point.
+    *
+    * @param p          point to encode
+    * @param compressed if true, generates a compressed point encoding
+    */
+  def encodePoint(p: Ecp, compressed: Boolean): Array[Byte] = Platform.encodePoint(p, compressed)
+
+  /** A [[Curve]] instance describing the elliptic curve of the point p
+    *
+    * @param p the elliptic curve point
+    */
+  def getCurve(p: Ecp): Curve = Platform.getCurve(p)
+
   /** Returns the x-coordinate.
     *
     * Caution: depending on the curve's coordinate system, this may not be the same value as in an

interpreter/src/main/scala/sigmastate/crypto/Platform.scala

@@ -1,12 +1,17 @@
 package sigmastate.crypto
 
 import org.bouncycastle.crypto.ec.CustomNamedCurves
-import org.bouncycastle.math.ec.{ECFieldElement, ECPoint}
+import org.bouncycastle.math.ec.{ECPoint, ECFieldElement, ECCurve}
 
 import java.math.BigInteger
 
 /** JVM specific implementation of crypto methods*/
 object Platform {
+  /** Description of elliptic curve of point `p` which belongs to the curve.
+    * @param p the elliptic curve point
+    */
+  def getCurve(p: Ecp): Curve = Curve(p.value.getCurve)
+
   /** Returns the x-coordinate.
     *
     * Caution: depending on the curve's coordinate system, this may not be the same value as in an
@@ -46,6 +51,12 @@ object Platform {
   /** Returns byte representation of the given field element. */
   def encodeFieldElem(p: ECFieldElem): Array[Byte] = p.value.getEncoded
 
+  /** Byte representation of the given point.
+    * @param p point to encode
+    * @param compressed if true, generates a compressed point encoding
+    */
+  def encodePoint(p: Ecp, compressed: Boolean): Array[Byte] = p.value.getEncoded(compressed)
+
   /** Returns the value of bit 0 in BigInteger representation of this point. */
   def signOf(p: ECFieldElem): Boolean = p.value.testBitZero()
 
@@ -94,6 +105,11 @@ object Platform {
   /** Negate a point. */
   def negatePoint(p: Ecp): Ecp = Ecp(p.value.negate())
 
+  /** Wrapper for curve descriptor. Serves as the concrete implementation of the
+    * [[sigmastate.crypto.Curve]] type in JVM.
+    */
+  case class Curve(private[crypto] val value: ECCurve)
+
   /** Wrapper for point type. */
   case class Ecp(private[crypto] val value: ECPoint)
 

interpreter/src/main/scala/sigmastate/crypto/package.scala

@@ -1,8 +1,12 @@
 package sigmastate
 
 package object crypto {
+  /** Instance of Elliptic Curve descriptor. */
+  type Curve = Platform.Curve
+
   /** Instance of Elliptic Curve point. */
   type Ecp = Platform.Ecp
+
   /** Instance of Elliptic Curve field element. */
   type ECFieldElem = Platform.ECFieldElem
 }