added HKDF, version will be 0.9.3

src/commonTest/kotlin/KDFTest.kt

@@ -8,6 +8,7 @@
  * real dot sergeych at gmail.
  */
 
+import com.ionspin.kotlin.crypto.util.encodeToUByteArray
 import kotlinx.coroutines.test.runTest
 import net.sergeych.crypto2.Hash
 import net.sergeych.crypto2.KDF
@@ -133,4 +134,84 @@ class KDFTest {
         assertEquals(96, longKdf.deriveFromBytes(source).size)
     }
 
+    @Test
+    fun hkdfDeriveFromBytesTest() = runTest {
+        initCrypto()
+        val source = "strong source bytes with enough entropy".encodeToUByteArray()
+        val salt = "stored public salt".encodeToUByteArray()
+        val info = "crypto2:test".encodeToUByteArray()
+        val kdf = KDF.HKDF(Hash.Sha3_256, salt, info, 80)
+
+        val b1 = kdf.deriveFromBytes(source)
+        val b2 = kdf.deriveFromBytes(source)
+        val b3 = kdf.deriveFromBytes(source + 1u)
+        val b4 = kdf.copy(info = "crypto2:other".encodeToUByteArray()).deriveFromBytes(source)
+        val expected = hexToUBytes(
+            "580cfd4eb588312097c9e43852d62bec9aff988591e2e5f721a2facc80c3c494" +
+                    "d3487b81e19f71611bdebb9983b94e058c9f0c38bc226b9b895eb554d17446b" +
+                    "672e12c7e2c36683807cd1e8d67ada0f7"
+        )
+
+        assertEquals(80, b1.size)
+        assertContentEquals(expected, b1)
+        assertContentEquals(b1, b2)
+        assertFalse { b1 contentEquals b3 }
+        assertFalse { b1 contentEquals b4 }
+    }
+
+    @Test
+    fun hkdfParametersCompareArraysByContentTest() = runTest {
+        initCrypto()
+        val k1 = KDF.HKDF(
+            Hash.Sha3_384,
+            "salt".encodeToUByteArray(),
+            "info".encodeToUByteArray(),
+            42
+        )
+        val k2 = KDF.HKDF(
+            Hash.Sha3_384,
+            "salt".encodeToUByteArray(),
+            "info".encodeToUByteArray(),
+            42
+        )
+
+        assertEquals(k1, k2)
+        assertEquals(k1.hashCode(), k2.hashCode())
+    }
+
+    @Test
+    fun hkdfRejectsInvalidParametersTest() = runTest {
+        initCrypto()
+
+        assertThrows<IllegalArgumentException> {
+            KDF.HKDF(Hash.Sha3_256, keySize = 0)
+        }
+        assertThrows<IllegalArgumentException> {
+            KDF.HKDF(Hash.Sha3AndBlake, keySize = 32)
+        }
+        assertThrows<IllegalArgumentException> {
+            KDF.HKDF(Hash.Sha3_256, keySize = 32 * 255 + 1)
+        }
+        assertThrows<IllegalArgumentException> {
+            KDF.HKDF(Hash.Sha3_256, keySize = 32).deriveFromBytes(ubyteArrayOf())
+        }
+    }
+
+    @Test
+    fun hkdfDoesNotDeriveFromPasswordTest() = runTest {
+        initCrypto()
+        val kdf = KDF.HKDF(keySize = 32)
+
+        assertThrows<UnsupportedOperationException> {
+            kdf.deriveKey("password")
+        }
+    }
+
+}
+
+private fun hexToUBytes(hex: String): UByteArray {
+    require(hex.length % 2 == 0) { "hex string should have even length" }
+    return UByteArray(hex.length / 2) {
+        hex.substring(it * 2, it * 2 + 2).toInt(16).toUByte()
+    }
 }