implement keccak

2025-11-09 20:53:01 +01:00
parent 88d673922a
commit e3619a2df1
7 changed files with 149 additions and 0 deletions
--- a/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt
@@ -0,0 +1,113 @@
+package com.infendro.hash.keccak
+
+import com.infendro.bytearray.ByteOrder.LITTLE_ENDIAN
+import com.infendro.bytearray.addAll
+import com.infendro.bytearray.toByteArray
+import com.infendro.bytearray.toULongArray
+import com.infendro.hash.HashFunction
+import kotlin.math.min
+
+@Suppress("UNUSED")
+open class Keccak internal constructor(
+    override val bytes: Int,
+    private val rate: Int,
+    private val domain: Byte,
+) : HashFunction() {
+    init {
+        if (rate % 8 != 0) {
+            throw IllegalArgumentException("rate must be divisible by 8")
+        }
+    }
+
+    private val rc = ulongArrayOf(
+        0x0000000000000001UL, 0x0000000000008082UL, 0x800000000000808aUL, 0x8000000080008000UL,
+        0x000000000000808bUL, 0x0000000080000001UL, 0x8000000080008081UL, 0x8000000000008009UL,
+        0x000000000000008aUL, 0x0000000000000088UL, 0x0000000080008009UL, 0x000000008000000aUL,
+        0x000000008000808bUL, 0x800000000000008bUL, 0x8000000000008089UL, 0x8000000000008003UL,
+        0x8000000000008002UL, 0x8000000000000080UL, 0x000000000000800aUL, 0x800000008000000aUL,
+        0x8000000080008081UL, 0x8000000000008080UL, 0x0000000080000001UL, 0x8000000080008008UL
+    )
+
+    private val rotation = arrayOf(
+        intArrayOf(0, 36, 3, 41, 18),
+        intArrayOf(1, 44, 10, 45, 2),
+        intArrayOf(62, 6, 43, 15, 61),
+        intArrayOf(28, 55, 25, 21, 56),
+        intArrayOf(27, 20, 39, 8, 14),
+    )
+
+    override fun hash(
+        value: ByteArray,
+    ): ByteArray {
+        val paddedValue = buildList {
+            addAll(value)
+            add(domain)
+            while ((size % rate) != (rate - 1)) {
+                add(0x00.toByte())
+            }
+            add(0x80.toByte())
+        }
+
+        val state = ULongArray(25)
+
+        // absorb
+        val chunks = paddedValue
+            .chunked(rate)
+        for (chunk in chunks) {
+            val numbers = chunk.toULongArray(LITTLE_ENDIAN)
+            for ((i, number) in numbers.withIndex()) {
+                state[i] = state[i] xor number
+            }
+            permute(state)
+        }
+
+        // squeeze
+        return buildList(bytes) {
+            var i = 0
+            while (size < bytes) {
+                if (i == rate / 8) {
+                    permute(state)
+                    i = 0
+                }
+                addAll(
+                    state[i++].toByteArray(LITTLE_ENDIAN)
+                        .take(min(bytes - size, 8))
+                )
+            }
+        }.toByteArray()
+    }
+
+    private fun permute(
+        a: ULongArray,
+    ) {
+        val b = ULongArray(25)
+        val c = ULongArray(5)
+        val d = ULongArray(5)
+
+        repeat(24) { round ->
+            // θ
+            for (x in 0..4) {
+                c[x] = a[x] xor a[x + 5] xor a[x + 10] xor a[x + 15] xor a[x + 20]
+            }
+            for (x in 0..4) {
+                d[x] = c[(x + 4) % 5] xor c[(x + 1) % 5].rotateLeft(1)
+            }
+            for (x in 0..4) for (y in 0..4) {
+                a[x + 5 * y] = a[x + 5 * y] xor d[x]
+            }
+
+            // ρ and π
+            for (x in 0..4) for (y in 0..4) {
+                b[y + 5 * ((2 * x + 3 * y) % 5)] = a[x + 5 * y].rotateLeft(rotation[x][y])
+            }
+
+            // χ
+            for (x in 0..4) for (y in 0..4) {
+                a[x + 5 * y] = b[x + 5 * y] xor ((b[((x + 1) % 5) + 5 * y].inv()) and b[((x + 2) % 5) + 5 * y])
+            }
+
+            // ι
+            a[0] = a[0] xor rc[round]
+        }
+    }
+}