Cleanup GroupCommon.

Remove unused methods.
Remove ZERO_MOD_P, TWO_MOD_P, Q_MOD_P, uIntToElementModP().
Remove inBoundsNoZero(), q.powQ(), gPowPSmall(), isZero() is Q only.

egklib/src/commonMain/kotlin/electionguard/core/Base16.kt

@@ -1,5 +1,6 @@
 package electionguard.core
 
+import electionguard.core.Base16.fromHex
 import io.github.oshai.kotlinlogging.KotlinLogging
 
 /**
@@ -88,5 +89,11 @@ object Base16 {
      */
     fun String.fromHexSafe(): ByteArray =
         fromHex() ?: throw IllegalArgumentException("fromHexSafe invalid input= '$this'")
+}
 
-}
+/**
+ * Converts a base-16 (hexadecimal) string to an [ElementModP]. Returns null if the number is out of
+ * bounds or the string is malformed.
+ */
+fun GroupContext.base16ToElementModP(s: String): ElementModP? =
+    s.fromHex()?.let { binaryToElementModP(it) }

egklib/src/commonMain/kotlin/electionguard/core/Base64.kt

@@ -104,8 +104,7 @@ object Base64 {
 
         /**
          * Encodes all bytes from the specified byte array into a newly-allocated byte array using
-         * the [Base64] encoding scheme. The returned byte array is of the length of the resulting
-         * bytes.
+         * the [Base64] encoding scheme. The returned byte array is of the length of the resulting bytes.
          *
          * @param src the byte array to encode
          * @param useBase64URL use Base64URL else use Base64

egklib/src/commonMain/kotlin/electionguard/core/ElGamalCiphertext.kt

@@ -89,6 +89,7 @@ fun List<ElGamalCiphertext>.add(other: List<ElGamalCiphertext>): List<ElGamalCip
     return result
 }
 
+// TODO what happens if nonce is small enough to take the log of?
 fun Int.encrypt(
     keypair: ElGamalKeypair,
     nonce: ElementModQ = keypair.context.randomElementModQ(minimum = 1)

egklib/src/commonMain/kotlin/electionguard/core/ElGamalKeys.kt

@@ -58,7 +58,7 @@ class ElGamalPublicKey(inputKey: ElementModP) {
 
 /**
  * A wrapper around an ElementModQ that allows us to hang onto a pre-computed [negativeKey]
- * (i.e., the additive inverse mod `q`). The secret key must be in [2, Q).
+ * (i.e., the additive inverse mod q). The secret key must be in [2, Q).
  */
 class ElGamalSecretKey(val key: ElementModQ) {
     init {

egklib/src/commonMain/kotlin/electionguard/core/GroupCommon.kt

@@ -1,10 +1,7 @@
 package electionguard.core
 
 import electionguard.ballot.ElectionConstants
-import electionguard.core.Base16.fromHex
 import electionguard.core.Base16.toHex
-import electionguard.core.Base64.fromBase64
-import electionguard.core.Base64.toBase64
 import io.github.oshai.kotlinlogging.KotlinLogging
 
 private val logger = KotlinLogging.logger("GroupCommon")
@@ -77,15 +74,9 @@ interface GroupContext {
      */
     val constants: ElectionConstants
 
-    /** Useful constant: zero mod p */
-    val ZERO_MOD_P: ElementModP
-
     /** Useful constant: one mod p */
     val ONE_MOD_P: ElementModP
 
-    /** Useful constant: two mod p */
-    val TWO_MOD_P: ElementModP
-
     /** Useful constant: the group generator */
     val G_MOD_P: ElementModP
 
@@ -95,9 +86,6 @@ interface GroupContext {
     /** Useful constant: the group generator, squared */
     val G_SQUARED_MOD_P: ElementModP
 
-    /** Useful constant: the modulus of the ElementModQ group */
-    val Q_MOD_P: ElementModP
-
     /** Useful constant: zero mod q */
     val ZERO_MOD_Q: ElementModQ
 
@@ -107,21 +95,13 @@ interface GroupContext {
     /** Useful constant: two mod q */
     val TWO_MOD_Q: ElementModQ
 
-    /**
-     * Useful constant: the maximum number of bytes to represent any element mod p when serialized
-     * as a `ByteArray`.
-     */
+    /** The maximum number of bytes to represent any element mod p when serialized as a ByteArray. */
     val MAX_BYTES_P: Int
 
-    /**
-     * Useful constant: the maximum number of bytes to represent any element mod q when serialized
-     * as a `ByteArray`.
-     */
+    /** The maximum number of bytes to represent any element mod q when serialized as a ByteArray. */
     val MAX_BYTES_Q: Int
 
-    /**
-     * Useful constant: the number of bits it takes to represent any element mod p.
-     */
+    /** Useful constant: the number of bits it takes to represent any element mod p. */
     val NUM_P_BITS: Int
 
     /**
@@ -174,9 +154,6 @@ interface GroupContext {
     /** Converts a long to an ElementModQ, with optimizations when possible for small integers */
     fun uLongToElementModQ(i: ULong): ElementModQ
 
-    /** Converts an integer to an ElementModP, with optimizations when possible for small integers */
-    fun uIntToElementModP(i: UInt): ElementModP
-
     /**
      * Computes the sum of the given elements, mod q; this can be faster than using the addition
      * operation for large numbers of inputs by potentially reusing scratch-space memory.
@@ -185,23 +162,39 @@ interface GroupContext {
 
     /**
      * Computes the product of the given elements, mod p; this can be faster than using the
-     * multiplication operation for large numbers of inputs by potentially reusing scratch-space
-     * memory.
+     * multiplication operation for large numbers of inputs by potentially reusing scratch-space memory.
      */
     fun Iterable<ElementModP>.multP(): ElementModP
 
     /** Computes G^e mod p, where G is our generator */
-    fun gPowP(e: ElementModQ): ElementModP
+    fun gPowP(exp: ElementModQ): ElementModP
 
     /**
      * 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)
      * 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. TODO sidechannel attack? */
     fun getAndClearOpCounts(): Map<String, Int>
 }
@@ -222,17 +215,6 @@ interface Element {
      */
     fun inBounds(): Boolean
 
-    /**
-     * 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 [1, N)
-     * where N is the group modulus.
-     */
-    fun inBoundsNoZero(): Boolean
-
-    /** Checks whether this element is zero. */
-    fun isZero(): Boolean
-
     /** Converts from any [Element] to a big-endian [ByteArray] representation. */
     fun byteArray(): ByteArray
 
@@ -252,9 +234,6 @@ interface ElementModQ : Element, Comparable<ElementModQ> {
     /** Computes the additive inverse */
     operator fun unaryMinus(): ElementModQ
 
-    /** Computes b^e mod q. LOOK seems to be not ever used */
-    infix fun powQ(e: ElementModQ): ElementModQ
-
     /** Finds the multiplicative inverse */
     fun multInv(): ElementModQ
 
@@ -263,6 +242,9 @@ interface ElementModQ : Element, Comparable<ElementModQ> {
 
     /** Allows elements to be compared (<, >, <=, etc.) using the usual arithmetic operators. */
     override operator fun compareTo(other: ElementModQ): Int
+
+    /** Checks whether this element is zero. */
+    fun isZero(): Boolean
 }
 
 interface ElementModP : Element, Comparable<ElementModP> {
@@ -273,7 +255,7 @@ interface ElementModP : Element, Comparable<ElementModP> {
     fun isValidResidue(): Boolean
 
     /** Computes b^e mod p */
-    infix fun powP(e: ElementModQ): ElementModP
+    infix fun powP(exp: ElementModQ): ElementModP
 
     /** Modular multiplication */
     operator fun times(other: ElementModP): ElementModP
@@ -299,7 +281,7 @@ interface ElementModP : Element, Comparable<ElementModP> {
 
     /** Short version of the String for readability */
     fun toStringShort(): String {
-        val s = base16()
+        val s = toHex()
         val len = s.length
         return "${s.substring(0, 7)}...${s.substring(len-8, len)}"
     }
@@ -320,68 +302,6 @@ interface MontgomeryElementModP {
     val context: GroupContext
 }
 
-/**
- * Converts a base-16 (hexadecimal) string to an [ElementModP]. Returns null if the number is out of
- * bounds or the string is malformed.
- */
-fun GroupContext.base16ToElementModP(s: String): ElementModP? =
-    s.fromHex()?.let { binaryToElementModP(it) }
-
-/**
- * Converts a base-16 (hexadecimal) string to an [ElementModQ]. Returns null if the number is out of
- * bounds or the string is malformed.
- */
-fun GroupContext.base16ToElementModQ(s: String): ElementModQ? =
-    s.fromHex()?.let { binaryToElementModQ(it) }
-
-/**
- * Converts a base-16 (hexadecimal) string to an [ElementModP]. Guarantees the result is in [0, P),
- * by computing the result mod P.
- */
-fun GroupContext.base16ToElementModPsafe(s: String): ElementModP =
-    s.fromHex()?.let { binaryToElementModPsafe(it) } ?: ZERO_MOD_P
-
-/**
- * Converts a base-16 (hexadecimal) string to an [ElementModQ]. Guarantees the result is in [0, Q),
- * by computing the result mod Q.
- */
-fun GroupContext.base16ToElementModQsafe(s: String): ElementModQ =
-    s.fromHex()?.let { binaryToElementModQsafe(it) } ?: ZERO_MOD_Q
-
-/**
- * Converts a base-64 string to an [ElementModP]. Returns null if the number is out of bounds or the
- * string is malformed.
- */
-fun GroupContext.base64ToElementModP(s: String): ElementModP? =
-    s.fromBase64()?.let { binaryToElementModP(it) }
-
-/**
- * Converts a base-64 string to an [ElementModQ]. Returns null if the number is out of bounds or the
- * string is malformed.
- */
-fun GroupContext.base64ToElementModQ(s: String): ElementModQ? =
-    s.fromBase64()?.let { binaryToElementModQ(it) }
-
-/**
- * Converts a base-64 string to an [ElementModP]. Guarantees the result is in [0, P), by computing
- * the result mod P.
- */
-fun GroupContext.base64ToElementModPsafe(s: String): ElementModP =
-    s.fromBase64()?.let { binaryToElementModPsafe(it) } ?: ZERO_MOD_P
-
-/**
- * Converts a base-64 string to an [ElementModQ]. Guarantees the result is in [0, Q), by computing
- * the result mod Q.
- */
-fun GroupContext.base64ToElementModQsafe(s: String): ElementModQ =
-    s.fromBase64()?.let { binaryToElementModQsafe(it) } ?: ZERO_MOD_Q
-
-/** Converts from any [Element] to a base64 string representation. */
-fun Element.base64(): String = byteArray().toBase64()
-
-/** Converts from any [Element] to a base16 (hexadecimal) string representation. */
-fun Element.base16(): String = byteArray().toHex()
-
 /** Converts an integer to an ElementModQ, with optimizations when possible for small integers */
 fun Int.toElementModQ(ctx: GroupContext) =
     when {
@@ -400,28 +320,6 @@ fun Long.toElementModQ(ctx: GroupContext) =
         else -> ctx.uLongToElementModQ(this.toULong())
     }
 
-/**
- * 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 GroupContext.randomElementModQ(minimum: Int = 0) =
-    binaryToElementModQsafe(randomBytes(MAX_BYTES_Q), minimum)
-
-/**
- * We often want to raise g to small powers, for which we've conveniently pre-computed the answers.
- * This function will fall back to use [GroupContext.gPowP] if the input isn't precomputed.
- */
-fun GroupContext.gPowPSmall(e: Int) =
-    when {
-        e == 0 -> ONE_MOD_P
-        e == 1 -> G_MOD_P
-        e == 2 -> G_SQUARED_MOD_P
-        e < 0 -> throw ArithmeticException("not defined for negative values")
-        else -> gPowP(e.toElementModQ(this))
-    }
-
 /**
  * Verifies that every element has a compatible [GroupContext] and returns the first context.
  *
@@ -462,7 +360,7 @@ fun ElementModP.dLogG(maxResult: Int = -1): Int? = context.dLogG(this, maxResult
  * `acceleration` parameter, to specify the speed versus memory tradeoff for subsequent computation.
  * See [PowRadixOption] for details. Note that this function can return `null`, which indicates that
  * the [ElectionConstants] were incompatible with this particular library.
- */
+ *
 fun ElectionConstants.toGroupContext(
     acceleration: PowRadixOption = PowRadixOption.LOW_MEMORY_USE
 ) : GroupContext? {
@@ -481,6 +379,7 @@ fun ElectionConstants.toGroupContext(
         }
     }
 }
+*/
 
 /**
  * Computes the sum of the given elements, mod q; this can be faster than using the addition

egklib/src/commonMain/kotlin/electionguard/json/GuardianJsonR.kt

@@ -43,7 +43,7 @@ fun GuardianJsonR.import(group: GroupContext, errs : ErrorMessages) : GuardianR?
 fun GuardianR.convert(group: GroupContext) = Guardian(
     this.name,
     this.i,
-    //     Schnorr proof is missing - fake it
+    //     Schnorr proof is missing - fake it TODO WTF?
     this.coefficient_commitments.map { SchnorrProof(it, group.ONE_MOD_Q, group.TWO_MOD_Q) }
 )
 

egklib/src/commonMain/kotlin/electionguard/verifier/VerifyTally.kt

@@ -39,12 +39,12 @@ class VerifyTally(
                     if (selection.encryptedVote.data != accum.data) {
                         errs.add("  8.B  Ballot Aggregation does not match: $key")
                     }
-                } else {
+                } /* else {
                     // TODO what is it? is it needed? left over from placeholders ??
                     if (selection.encryptedVote.pad != group.ZERO_MOD_P || selection.encryptedVote.data != group.ZERO_MOD_P) {
                         errs.add("    Ballot Aggregation empty does not match $key")
                     }
-                }
+                } */
             }
         }