refactor, implement LCG

LCG ... Linear Congruential Generator

build.gradle.kts

@@ -25,6 +25,10 @@ kotlin {
             implementation(libs.bytearray)
         }
     }
+
+    compilerOptions {
+        freeCompilerArgs.add("-opt-in=kotlin.ExperimentalUnsignedTypes")
+    }
 }
 
 publishing {

gradle/libs.versions.toml

@@ -1,8 +1,8 @@
 [versions]
 kotlin = "2.1.20"
-hash = "1.2.2"
-mac = "1.1.2"
-bytearray = "1.1.1"
+hash = "1.3.2"
+mac = "1.2.0"
+bytearray = "1.2.2"
 
 [plugins]
 multiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }

src/commonMain/kotlin/com/infendro/random/HMAC.kt

@@ -1,53 +0,0 @@
-package com.infendro.random
-
-import com.infendro.bytearray.addAll
-import com.infendro.hash.HashFunction
-
-class HMAC internal constructor(
-    private val function: HashFunction,
-) : PRNG() {
-    private val random = Default
-    private val hmac = com.infendro.mac.HMAC(function)
-    private lateinit var K: ByteArray
-    private lateinit var V: ByteArray
-
-    init {
-        val bytes = random.nextBytes(function.bytes)
-        seed(bytes)
-    }
-
-    override fun seed(
-        seed: ByteArray,
-    ) {
-        K = ByteArray(function.bytes) { 0x00 }
-        V = ByteArray(function.bytes) { 0x01 }
-        reseed(seed)
-    }
-
-    override fun reseed(
-        entropy: ByteArray,
-    ) {
-        K = hmac.hash(K, V + byteArrayOf(0x00) + entropy)
-        V = hmac.hash(K, V)
-        K = hmac.hash(K, V + byteArrayOf(0x01) + entropy)
-        V = hmac.hash(K, V)
-    }
-
-    override fun generate(
-        count: Int,
-    ): ByteArray {
-        val bytes = buildList {
-            while (size < count) {
-                V = hmac.hash(K, V)
-                addAll(V)
-            }
-        }
-
-        K = hmac.hash(K, V + byteArrayOf(0x00))
-        V = hmac.hash(K, V)
-
-        return bytes
-            .take(count)
-            .toByteArray()
-    }
-}

src/commonMain/kotlin/com/infendro/random/csprng/CSPRNG.kt

@@ -0,0 +1,16 @@
+package com.infendro.random.csprng
+
+import com.infendro.hash.HashFunction
+import com.infendro.random.prng.PRNG
+
+abstract class CSPRNG : PRNG() {
+    abstract fun reseed(
+        entropy: UByteArray,
+    )
+
+    companion object {
+        fun HMAC(
+            function: HashFunction,
+        ) = com.infendro.random.csprng.HMAC(function)
+    }
+}

src/commonMain/kotlin/com/infendro/random/csprng/HMAC.kt

@@ -0,0 +1,48 @@
+package com.infendro.random.csprng
+
+import com.infendro.hash.HashFunction
+import kotlin.math.min
+import kotlin.properties.Delegates.notNull
+
+class HMAC internal constructor(
+    private val function: HashFunction,
+) : CSPRNG() {
+    private val hmac = com.infendro.mac.HMAC(function)
+
+    private var k: UByteArray by notNull()
+    private var v: UByteArray by notNull()
+
+    override fun seed(
+        seed: UByteArray,
+    ) {
+        k = UByteArray(function.bytes) { 0x00U }
+        v = UByteArray(function.bytes) { 0x01U }
+        reseed(seed)
+    }
+
+    override fun reseed(
+        entropy: UByteArray,
+    ) {
+        k = hmac.hash(k, v + ubyteArrayOf(0x00U) + entropy)
+        v = hmac.hash(k, v)
+        k = hmac.hash(k, v + ubyteArrayOf(0x01U) + entropy)
+        v = hmac.hash(k, v)
+    }
+
+    override fun generate(
+        count: Int,
+    ): UByteArray {
+        val bytes = buildList {
+            while (size < count) {
+                v = hmac.hash(k, v)
+
+                addAll(v.take(min(count - size, function.bytes)))
+            }
+        }.toUByteArray()
+
+        k = hmac.hash(k, v + ubyteArrayOf(0x00U))
+        v = hmac.hash(k, v)
+
+        return bytes
+    }
+}

src/commonMain/kotlin/com/infendro/random/prng/LCG.kt

@@ -0,0 +1,34 @@
+package com.infendro.random.prng
+
+import com.infendro.bytearray.padStart
+import com.infendro.bytearray.toUByteArray
+import com.infendro.bytearray.toULong
+import kotlin.math.min
+import kotlin.properties.Delegates
+
+class LCG internal constructor() : PRNG() {
+    private val a: ULong = 25214903917UL
+    private val c: ULong = 11UL
+    private val m: ULong = 1UL shl 48
+
+    private var x: ULong by Delegates.notNull()
+
+    override fun seed(
+        seed: UByteArray,
+    ) {
+        val s = seed.padStart(8, 0x00U).takeLast(8).toUByteArray()
+        x = s.toULong() % m
+    }
+
+    override fun generate(
+        count: Int,
+    ): UByteArray {
+        return buildList {
+            while (size < count) {
+                x = (a * x + c) % m
+
+                addAll(x.toUByteArray().takeLast(min(count - size, 6)))
+            }
+        }.toUByteArray()
+    }
+}

src/commonMain/kotlin/com/infendro/random/prng/PRNG.kt

@@ -1,21 +1,16 @@
-package com.infendro.random
+package com.infendro.random.prng
 
 import com.infendro.bytearray.toInt
-import com.infendro.hash.HashFunction
 import kotlin.random.Random
 
 abstract class PRNG : Random() {
     abstract fun seed(
-        seed: ByteArray,
-    )
-
-    abstract fun reseed(
-        entropy: ByteArray,
+        seed: UByteArray,
     )
 
     abstract fun generate(
         count: Int,
-    ): ByteArray
+    ): UByteArray
 
     override fun nextBits(
         bitCount: Int,
@@ -27,10 +22,6 @@ abstract class PRNG : Random() {
     }
 
     companion object {
-        fun HMAC(
-            function: HashFunction,
-        ): HMAC {
-            return com.infendro.random.HMAC(function)
-        }
+        fun LCG() = com.infendro.random.prng.LCG()
     }
 }