Rename ElementModP.isValidResidue() to isValidElement().

Element.inBounds() only applies to ElementModQ.
Remove group.isProductionStrength()
Remove binaryToElementModP(Q)safe, used only by randomElementModP(Q)

README.md

@@ -1,10 +1,10 @@
 [![License](https://img.shields.io/github/license/JohnLCaron/egk-ec)](https://github.com/JohnLCaron/egk-ec/blob/main/LICENSE.txt)
 ![GitHub branch checks state](https://img.shields.io/github/actions/workflow/status/JohnLCaron/egk-ec/unit-tests.yml)
-![Coverage](https://img.shields.io/badge/coverage-90.7%25%20LOC%20(6931/7639)-blue)
+![Coverage](https://img.shields.io/badge/coverage-90.8%25%20LOC%20(6930/7630)-blue)
 
 # ElectionGuard-Kotlin Elliptic Curve
 
-_last update 04/17/2024_
+_last update 04/24/2024_
 
 EGK Elliptic Curve (egk-ec) is an experimental implementation of [ElectionGuard](https://github.com/microsoft/electionguard), 
 [version 2.0](https://github.com/microsoft/electionguard/releases/download/v2.0/EG_Spec_2_0.pdf), 

src/main/kotlin/org/cryptobiotic/eg/core/ChaumPedersen.kt

@@ -142,8 +142,8 @@ fun ChaumPedersenRangeProofKnownNonce.verify(
 
     val (alpha, beta) = ciphertext
     results.add(
-        if (alpha.isValidResidue() && beta.isValidResidue()) Ok(true) else
-            Err("    5.A,6.A values not in Zp^r: alpha = ${alpha.inBounds()} beta = ${beta.inBounds()}")
+        if (alpha.isValidElement() && beta.isValidElement()) Ok(true) else
+            Err("    5.A,6.A values not in Zp^r: alpha = ${alpha.isValidElement()} beta = ${beta.isValidElement()}")
     )
 
     val expandedProofs = proofs.mapIndexed { j, proof ->

src/main/kotlin/org/cryptobiotic/eg/core/GroupContext.kt

@@ -1,8 +1,6 @@
 package org.cryptobiotic.eg.core
 
 import org.cryptobiotic.eg.core.Base16.toHex
-import org.cryptobiotic.eg.core.intgroup.PowRadixOption
-import org.cryptobiotic.eg.core.intgroup.ProductionMode
 import org.cryptobiotic.eg.election.ElectionConstants
 
 fun productionGroup(groupName: String = "P-256", useNative: Boolean = true): GroupContext {
@@ -16,11 +14,6 @@ fun productionGroup(groupName: String = "P-256", useNative: Boolean = true): Gro
  * encapsulate acceleration data structures that we'll use to support various operations.
  */
 interface GroupContext {
-    /**
-     * Returns whether we're using "production primes" (bigger, slower, secure) versus "test primes"
-     * (smaller, faster, but insecure).
-     */
-    fun isProductionStrength(): Boolean
 
     /** Useful constant: one mod p */
     val ONE_MOD_P: ElementModP
@@ -63,12 +56,6 @@ interface GroupContext {
      */
     fun isCompatible(ctx: GroupContext): Boolean
 
-    /** Converts a [ByteArray] to an [ElementModP]. Guarantees the result is in [minimum, P), by computing the result mod P. */
-    fun binaryToElementModPsafe(b: ByteArray, minimum: Int = 0): ElementModP
-
-    /** Converts a [ByteArray] to an [ElementModQ]. Guarantees the result is in [minimum, Q), by computing the result mod Q. */
-    fun binaryToElementModQsafe(b: ByteArray, minimum: Int = 0): ElementModQ
-
     /**
      * Converts a [ByteArray] to an [ElementModP], inverse of ElementModP.byteArray().
      * Returns null if the number is out of bounds or malformed.
@@ -77,9 +64,22 @@ interface GroupContext {
 
     /**
      * Converts a [ByteArray] to an [ElementModQ], inverse of ElementModQ.byteArray().
+     * Guarantees the result is in [0, Q), by computing the result mod Q.
      * Returns null if the number is out of bounds or malformed.
      */
-    fun binaryToElementModQ(b: ByteArray): ElementModQ?
+    fun binaryToElementModQ(b: ByteArray): ElementModQ
+
+    /**
+     * Returns a random number in [minimum, Q), where minimum defaults to zero. Promises to use a
+     * "secure" random number generator, such that the results are suitable for use as cryptographic keys.
+     */
+    fun randomElementModQ(minimum: Int = 0) : ElementModQ // = binaryToElementModQ(randomBytes(MAX_BYTES_Q), minimum)
+
+    /**
+     * Returns a random ElementModP. Promises to use a "secure" random number generator, such that
+     * the results are suitable for use as cryptographic keys.
+     */
+    fun randomElementModP() : ElementModP
 
     /** Converts an integer to an ElementModQ, with optimizations when possible for small integers */
     fun uIntToElementModQ(i: UInt): ElementModQ
@@ -115,29 +115,13 @@ interface GroupContext {
     /**
      * Given an element x for which there exists an e, such that g^e = x, this will find e,
      * so long as e is less than [maxResult], which if unspecified defaults to a platform-specific
-     * value designed not to consume too much memory (perhaps 10 million). This will consume O(e)
+     * value designed not to consume too much memory. This will consume O(e)
      * time, the first time, after which the results are memoized for all values between 0 and e,
      * for better future performance.
      * If the result is not found, null is returned.
      */
     fun dLogG(p: ElementModP, maxResult: Int = - 1): Int?
 
-    /**
-     * Returns a random number in [minimum, Q), where minimum defaults to zero. Promises to use a
-     * "secure" random number generator, such that the results are suitable for use as cryptographic keys.
-     * @throws IllegalArgumentException if the minimum is negative
-     */
-    fun randomElementModQ(minimum: Int = 0) =
-        binaryToElementModQsafe(randomBytes(MAX_BYTES_Q), minimum)
-
-    /**
-     * Returns a random number in [minimum, P), where minimum defaults to zero. Promises to use a
-     * "secure" random number generator, such that the results are suitable for use as cryptographic keys.
-     * @throws IllegalArgumentException if the minimum is negative
-     */
-    fun randomElementModP(minimum: Int = 0) =
-        binaryToElementModPsafe(randomBytes(MAX_BYTES_P), minimum)
-
     /** debugging operation counts. */
     fun getAndClearOpCounts(): Map<String, Int>
 }
@@ -150,14 +134,6 @@ interface Element {
      */
     val context: GroupContext
 
-    /**
-     * Normal computations should ensure that every [Element] is in the modular bounds defined by
-     * the group, but deserialization of hostile inputs or buggy code might not preserve this
-     * property, so it's valuable to have a way to check. This method allows anything in [0, N)
-     * where N is the group modulus.
-     */
-    fun inBounds(): Boolean
-
     /** Converts to a [ByteArray] representation. Inverse to group.binaryToElementModX(). */
     fun byteArray(): ByteArray
 
@@ -188,14 +164,15 @@ interface ElementModQ : Element, Comparable<ElementModQ> {
 
     /** Checks whether this element is zero. */
     fun isZero(): Boolean
+
+    /** Validate the element is in [0,Q) */
+    fun inBounds(): Boolean
 }
 
 interface ElementModP : Element, Comparable<ElementModP> {
-    /**
-     * Validates that this element is a quadratic residue, ie in Z_p^r.
-     * "Z_p^r is the set of r-th-residues in Z∗p", see spec 2.0 p.9
-     */
-    fun isValidResidue(): Boolean
+
+    /** Validates that this element is a member of the Group */
+    fun isValidElement(): Boolean
 
     /** Computes b^e mod p */
     infix fun powP(exp: ElementModQ): ElementModP

src/main/kotlin/org/cryptobiotic/eg/core/Schnorr.kt

@@ -16,7 +16,7 @@ data class SchnorrProof(
 
     init {
         compatibleContextOrFail(publicCommitment, challenge, response)
-        require(publicCommitment.isValidResidue()) // 2.A
+        require(publicCommitment.isValidElement()) // 2.A
     }
 
     // verification Box 2, p 23
@@ -30,7 +30,7 @@ data class SchnorrProof(
         // c wouldnt agree unless h = g^u
         // therefore, whoever generated v knows s
 
-        val inBoundsK = publicCommitment.isValidResidue() // 2.A
+        val inBoundsK = publicCommitment.isValidElement() // 2.A
         val inBoundsU = response.inBounds() // 2.B
         val validChallenge = c == challenge // 2.C
         val success = inBoundsK && inBoundsU && validChallenge

src/main/kotlin/org/cryptobiotic/eg/core/UInt256.kt

@@ -84,7 +84,7 @@ fun ByteArray.normalize(nbytes: Int): ByteArray {
  * beginning by computing "mod q".
  */
 fun UInt256.toElementModQ(context: GroupContext): ElementModQ =
-    context.binaryToElementModQsafe(bytes)
+    context.binaryToElementModQ(bytes)
 
 fun ElementModQ.toUInt256safe(): UInt256 = this.byteArray().toUInt256safe()
 fun ULong.toUInt256(): UInt256 = this.toByteArray().toUInt256safe()

src/main/kotlin/org/cryptobiotic/eg/core/ecgroup/EcElementModP.kt

@@ -23,11 +23,8 @@ class EcElementModP(val group: EcGroupContext, val ec: VecElementP): ElementModP
         return EcElementModP(group, ec.mul(inv))
     }
 
-    // TODO what does it mean to be in bounds ??
-    override fun inBounds(): Boolean = true
-
-    // TODO check this
-    override fun isValidResidue(): Boolean {
+    /** Validate that this element is a member of the elliptic curve Group.*/
+    override fun isValidElement(): Boolean {
         return group.vecGroup.isPointOnCurve(this.ec.x, this.ec.y)
     }
 

src/main/kotlin/org/cryptobiotic/eg/core/ecgroup/EcGroupContext.kt

@@ -1,6 +1,7 @@
 package org.cryptobiotic.eg.core.ecgroup
 
 import org.cryptobiotic.eg.core.*
+import org.cryptobiotic.eg.core.intgroup.toBigInteger
 import java.math.BigInteger
 import java.util.concurrent.atomic.AtomicInteger
 
@@ -19,29 +20,29 @@ class EcGroupContext(val name: String, useNative: Boolean = true): GroupContext
     override val ZERO_MOD_Q: ElementModQ = EcElementModQ(this, BigInteger.ZERO)
     override val ONE_MOD_Q: ElementModQ = EcElementModQ(this, BigInteger.ONE)
     override val TWO_MOD_Q: ElementModQ = EcElementModQ(this, BigInteger.TWO)
-    val NUM_Q_BITS: Int = vecGroup.qbitLength
 
     override val constants = vecGroup.constants
     val dlogg = DLogarithm(G_MOD_P)
 
-    // TODO whats difference with safe version?
     override fun binaryToElementModP(b: ByteArray): ElementModP? {
         val elem = vecGroup.elementFromByteArray(b)
         return if (elem != null) EcElementModP(this, elem) else null
     }
 
-    override fun binaryToElementModPsafe(b: ByteArray, minimum: Int): ElementModP {
-        return binaryToElementModP(b) ?: throw RuntimeException("invalid input")
-    }
-
-    override fun binaryToElementModQ(b: ByteArray): ElementModQ? {
+    override fun binaryToElementModQ(b: ByteArray): ElementModQ {
         return EcElementModQ(this, BigInteger(1, b))
     }
 
-    override fun binaryToElementModQsafe(b: ByteArray, minimum: Int): ElementModQ {
-        return EcElementModQ(this, BigInteger(1, b))
+    override fun randomElementModQ(minimum: Int) : ElementModQ {
+        val b = randomBytes(MAX_BYTES_Q)
+        val bigMinimum = if (minimum <= 0) BigInteger.ZERO else minimum.toBigInteger()
+        val tmp = b.toBigInteger().mod(vecGroup.order)
+        val big = if (tmp < bigMinimum) tmp + bigMinimum else tmp
+        return EcElementModQ(this, big)
     }
 
+    override fun randomElementModP() = EcElementModP(this, vecGroup.randomElement())
+
     override fun dLogG(p: ElementModP, maxResult: Int): Int? {
         require(p is EcElementModP)
         return dlogg.dLog(p, maxResult)
@@ -64,10 +65,6 @@ class EcGroupContext(val name: String, useNative: Boolean = true): GroupContext
         return (ctx is EcGroupContext) && name == ctx.name
     }
 
-    override fun isProductionStrength(): Boolean {
-        return true
-    }
-
     override fun uIntToElementModQ(i: UInt): ElementModQ {
         return EcElementModQ(this, BigInteger.valueOf(i.toLong()))
     }
@@ -85,8 +82,6 @@ class EcGroupContext(val name: String, useNative: Boolean = true): GroupContext
        return pees.fold(ONE_MOD_P) { a, b -> a * b }
     }
 
-    override fun randomElementModP(minimum: Int) = EcElementModP(this, vecGroup.randomElement())
-
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
         if (javaClass != other?.javaClass) return false

src/main/kotlin/org/cryptobiotic/eg/core/ecgroup/VecGroup.kt

@@ -94,6 +94,8 @@ open class VecGroup(
     fun elementFromByteArray(ba: ByteArray): VecElementP? = elementFromByteArray1(ba)
 
     val ffbyte: Byte = (-1).toByte()
+
+    // this is for serialization of both the x and y value.
     fun elementFromByteArray2(ba: ByteArray): VecElementP? {
         if (ba.size != 2*pbyteLength) return null
         val allff = ba.fold( true) { a, b -> a && (b == ffbyte) }
@@ -123,6 +125,7 @@ open class VecGroup(
         return makeVecModP(x, y)
     }
 
+    // this is for testing that 1 and 2 are equivilent
     fun elementFromByteArray1from2(ba: ByteArray): VecElementP? {
         if (ba.size != 2*pbyteLength) return null
         val allff = ba.fold( true) { a, b -> a && (b == ffbyte) }
@@ -132,6 +135,7 @@ open class VecGroup(
         return makeVecModP(x, y)
     }
 
+    // this value will always > 1, since 0, 1 are not on the curve.
     fun randomElement(): VecElementP {
         for (j in 0 until 1000) { // limited in case theres a bug
             try {