diff --git a/src/commonMain/kotlin/com/infendro/hash/HashFunction.kt b/src/commonMain/kotlin/com/infendro/hash/HashFunction.kt
index 676de51..34e40d9 100644
--- a/src/commonMain/kotlin/com/infendro/hash/HashFunction.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/HashFunction.kt
@@ -1,13 +1,13 @@
 package com.infendro.hash
 
-abstract class HashFunction {
-    abstract val bytes: Int
+interface HashFunction {
+    val bytes: Int
     val bits: Int
         get() = bytes * 8
 
-    abstract val block: Int
+    val block: Int
 
-    abstract fun hash(
+    fun hash(
         value: UByteArray,
     ): UByteArray
 }
diff --git a/src/commonMain/kotlin/com/infendro/hash/blake/Blake-224.kt b/src/commonMain/kotlin/com/infendro/hash/blake/Blake-224.kt
index d9765a3..68d02ef 100644
--- a/src/commonMain/kotlin/com/infendro/hash/blake/Blake-224.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/blake/Blake-224.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toUIntArray
 import com.infendro.hash.HashFunction
 
-object `Blake-224` : HashFunction() {
+object `Blake-224` : HashFunction {
     override val bytes: Int
         get() = 28
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/blake/Blake-256.kt b/src/commonMain/kotlin/com/infendro/hash/blake/Blake-256.kt
index 380d424..f55bf6e 100644
--- a/src/commonMain/kotlin/com/infendro/hash/blake/Blake-256.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/blake/Blake-256.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toUIntArray
 import com.infendro.hash.HashFunction
 
-object `Blake-256` : HashFunction() {
+object `Blake-256` : HashFunction {
     override val bytes: Int
         get() = 32
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/blake/Blake-384.kt b/src/commonMain/kotlin/com/infendro/hash/blake/Blake-384.kt
index 45518e3..47f9bcb 100644
--- a/src/commonMain/kotlin/com/infendro/hash/blake/Blake-384.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/blake/Blake-384.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toULongArray
 import com.infendro.hash.HashFunction
 
-object `Blake-384` : HashFunction() {
+object `Blake-384` : HashFunction {
     override val bytes: Int
         get() = 48
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/blake/Blake-512.kt b/src/commonMain/kotlin/com/infendro/hash/blake/Blake-512.kt
index d1329fb..9a1821c 100644
--- a/src/commonMain/kotlin/com/infendro/hash/blake/Blake-512.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/blake/Blake-512.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toULongArray
 import com.infendro.hash.HashFunction
 
-object `Blake-512` : HashFunction() {
+object `Blake-512` : HashFunction {
     override val bytes: Int
         get() = 64
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/blake2/Blake2b.kt b/src/commonMain/kotlin/com/infendro/hash/blake2/Blake2b.kt
index 0142418..95bc274 100644
--- a/src/commonMain/kotlin/com/infendro/hash/blake2/Blake2b.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/blake2/Blake2b.kt
@@ -7,7 +7,7 @@ import com.infendro.hash.HashFunction
 
 class Blake2b(
     override val bytes: Int,
-) : HashFunction() {
+) : HashFunction {
     init {
         if (bytes !in 1..64) throw IllegalArgumentException()
     }
diff --git a/src/commonMain/kotlin/com/infendro/hash/blake2/Blake2s.kt b/src/commonMain/kotlin/com/infendro/hash/blake2/Blake2s.kt
index b18c252..63460eb 100644
--- a/src/commonMain/kotlin/com/infendro/hash/blake2/Blake2s.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/blake2/Blake2s.kt
@@ -7,7 +7,7 @@ import com.infendro.hash.HashFunction
 
 class Blake2s(
     override val bytes: Int,
-) : HashFunction() {
+) : HashFunction {
     init {
         if (bytes !in 1..32) throw IllegalArgumentException()
     }
diff --git a/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt b/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt
index 7d92f9e..15a0cb2 100644
--- a/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/keccak/Keccak.kt
@@ -6,16 +6,11 @@ import com.infendro.bytearray.toULongArray
 import com.infendro.hash.HashFunction
 import kotlin.math.min
 
-open class Keccak(
+abstract class Keccak(
     override val bytes: Int,
     private val rate: Int,
     private val domain: UByte,
-) : HashFunction() {
-    init {
-        if (bytes < 1) throw IllegalArgumentException()
-        if (rate !in 8..168) throw IllegalArgumentException()
-    }
-
+) : HashFunction {
     override val block: Int
         get() = rate
 
@@ -108,7 +103,7 @@ open class Keccak(
         }
     }
 
-    fun squeeze(
+    private fun squeeze(
         state: ULongArray,
     ): UByteArray {
         return buildList {
diff --git a/src/commonMain/kotlin/com/infendro/hash/md/MD5.kt b/src/commonMain/kotlin/com/infendro/hash/md/MD5.kt
index a34127c..132ed5c 100644
--- a/src/commonMain/kotlin/com/infendro/hash/md/MD5.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/md/MD5.kt
@@ -5,7 +5,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toUIntArray
 import com.infendro.hash.HashFunction
 
-object MD5 : HashFunction() {
+object MD5 : HashFunction {
     override val bytes: Int
         get() = 16
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/sha1/SHA1.kt b/src/commonMain/kotlin/com/infendro/hash/sha1/SHA1.kt
index c0f4c16..236b0b5 100644
--- a/src/commonMain/kotlin/com/infendro/hash/sha1/SHA1.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/sha1/SHA1.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toUIntArray
 import com.infendro.hash.HashFunction
 
-object SHA1 : HashFunction() {
+object SHA1 : HashFunction {
     override val bytes: Int
         get() = 20
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-224.kt b/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-224.kt
index f051958..d08ed67 100644
--- a/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-224.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-224.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toUIntArray
 import com.infendro.hash.HashFunction
 
-object `SHA-224` : HashFunction() {
+object `SHA-224` : HashFunction {
     override val bytes: Int
         get() = 28
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-256.kt b/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-256.kt
index e97b49d..b47a39c 100644
--- a/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-256.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-256.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toUIntArray
 import com.infendro.hash.HashFunction
 
-object `SHA-256` : HashFunction() {
+object `SHA-256` : HashFunction {
     override val bytes: Int
         get() = 32
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-384.kt b/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-384.kt
index b2c6fa6..fb536cf 100644
--- a/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-384.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-384.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toULongArray
 import com.infendro.hash.HashFunction
 
-object `SHA-384` : HashFunction() {
+object `SHA-384` : HashFunction {
     override val bytes: Int
         get() = 48
 
diff --git a/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-512.kt b/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-512.kt
index 3df9481..c0dc89c 100644
--- a/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-512.kt
+++ b/src/commonMain/kotlin/com/infendro/hash/sha2/SHA-512.kt
@@ -4,7 +4,7 @@ import com.infendro.bytearray.toUByteArray
 import com.infendro.bytearray.toULongArray
 import com.infendro.hash.HashFunction
 
-object `SHA-512` : HashFunction() {
+object `SHA-512` : HashFunction {
     override val bytes: Int
         get() = 64