Added _kdf_ all implementations and a simple and probably pointless test, also noted which functions are not available as they are not part of LazySodium

multiplatform-crypto-libsodium-bindings/src/commonMain/kotlin/com.ionspin.kotlin.crypto/kdf/Kdf.kt

@@ -0,0 +1,33 @@
+package com.ionspin.kotlin.crypto.kdf
+
+/**
+ * Created by Ugljesa Jovanovic (jovanovic.ugljesa@gmail.com) on 16/Sep/2020
+ */
+const val crypto_kdf_PRIMITIVE = "blake2b"
+const val crypto_kdf_BYTES_MIN = 16
+const val crypto_kdf_BYTES_MAX = 64
+const val crypto_kdf_CONTEXTBYTES = 8
+const val crypto_kdf_KEYBYTES = 32
+
+expect object Kdf {
+    /**
+     * The crypto_kdf_derive_from_key() function derives a subkey_id-th subkey subkey of length subkey_len bytes using
+     * the master key key and the context ctx.
+     * subkey_id can be any value up to (2^64)-1.
+     * subkey_len has to be between crypto_kdf_BYTES_MIN (inclusive) and crypto_kdf_BYTES_MAX (inclusive).
+     * Similar to a type, the context ctx is a 8 characters string describing what the key is going to be used for.
+     * Its purpose is to mitigate accidental bugs by separating domains. The same function used with the same key but
+     * in two distinct contexts is likely to generate two different outputs.
+     * Contexts don't have to be secret and can have a low entropy.
+     * Examples of contexts include UserName, __auth__, pictures and userdata.
+     * They must be crypto_kdf_CONTEXTBYTES bytes long.
+     * If more convenient, it is also fine to use a single global context for a whole application. This will still
+     * prevent the same keys from being mistakenly used by another application.
+     */
+    fun deriveFromKey(subkeyId: Int, subkeyLength: Int, context: String, masterKey: UByteArray) : UByteArray
+
+    /**
+     * The crypto_kdf_keygen() function creates a master key.
+     */
+    fun keygen() : UByteArray
+}

multiplatform-crypto-libsodium-bindings/src/commonTest/kotlin/com/ionspin/kotlin/crypto/kdf/KdfTest.kt

@@ -0,0 +1,34 @@
+package com.ionspin.kotlin.crypto.kdf
+
+import com.ionspin.kotlin.crypto.LibsodiumInitializer
+import kotlin.test.Test
+import kotlin.test.assertFails
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+/**
+ * Created by Ugljesa Jovanovic (jovanovic.ugljesa@gmail.com) on 16/Sep/2020
+ */
+class KdfTest {
+    @Test
+    fun testKdf() {
+        LibsodiumInitializer.initializeWithCallback {
+            val masterKey = Kdf.keygen()
+            val subkey1 = Kdf.deriveFromKey(1, crypto_kdf_BYTES_MAX, "test1234", masterKey)
+            val subkey2 = Kdf.deriveFromKey(2, crypto_kdf_BYTES_MAX, "test1234", masterKey)
+
+            assertTrue {
+                subkey1.size == crypto_kdf_BYTES_MAX &&
+                        subkey2.size == crypto_kdf_BYTES_MAX
+            }
+
+            val repeatSubkey1 = Kdf.deriveFromKey(1, crypto_kdf_BYTES_MAX, "test1234", masterKey)
+            assertTrue {
+                subkey1.contentEquals(repeatSubkey1)
+            }
+            assertFalse {
+                subkey1.contentEquals(subkey2)
+            }
+        }
+    }
+}

multiplatform-crypto-libsodium-bindings/src/jsMain/kotlin/com/ionspin/kotlin/crypto/JsSodiumInterface.kt

@@ -174,7 +174,15 @@ interface JsSodiumInterface {
     fun crypto_sign_verify_detached(signature: Uint8Array, message: Uint8Array, publicKey: Uint8Array) : Boolean
 
 
-    // ---- Sign end
+    // ---- Sign end ----
+
+
+    // ---- KDF ----
+
+    fun crypto_kdf_derive_from_key(subkey_len: UInt, subkeyId : UInt, ctx: String, key: Uint8Array) : Uint8Array
+    fun crypto_kdf_keygen() : Uint8Array
+
+    // ---- KDF end -----
 
     //util
     fun memzero(array: Uint8Array)

multiplatform-crypto-libsodium-bindings/src/jsMain/kotlin/com/ionspin/kotlin/crypto/kdf/Kdf.kt

@@ -0,0 +1,43 @@
+package com.ionspin.kotlin.crypto.kdf
+
+import com.ionspin.kotlin.crypto.getSodium
+import ext.libsodium.com.ionspin.kotlin.crypto.toUByteArray
+import ext.libsodium.com.ionspin.kotlin.crypto.toUInt8Array
+
+actual object Kdf {
+    /**
+     * The crypto_kdf_derive_from_key() function derives a subkey_id-th subkey subkey of length subkey_len bytes using
+     * the master key key and the context ctx.
+     * subkey_id can be any value up to (2^64)-1.
+     * subkey_len has to be between crypto_kdf_BYTES_MIN (inclusive) and crypto_kdf_BYTES_MAX (inclusive).
+     * Similar to a type, the context ctx is a 8 characters string describing what the key is going to be used for.
+     * Its purpose is to mitigate accidental bugs by separating domains. The same function used with the same key but
+     * in two distinct contexts is likely to generate two different outputs.
+     * Contexts don't have to be secret and can have a low entropy.
+     * Examples of contexts include UserName, __auth__, pictures and userdata.
+     * They must be crypto_kdf_CONTEXTBYTES bytes long.
+     * If more convenient, it is also fine to use a single global context for a whole application. This will still
+     * prevent the same keys from being mistakenly used by another application.
+     */
+    actual fun deriveFromKey(
+        subkeyId: Int,
+        subkeyLength: Int,
+        context: String,
+        masterKey: UByteArray
+    ): UByteArray {
+        return getSodium().crypto_kdf_derive_from_key(
+            subkeyLength.toUInt(),
+            subkeyId.toUInt(),
+            context,
+            masterKey.toUInt8Array()
+        ).toUByteArray()
+    }
+
+    /**
+     * The crypto_kdf_keygen() function creates a master key.
+     */
+    actual fun keygen(): UByteArray {
+        return getSodium().crypto_kdf_keygen().toUByteArray()
+    }
+
+}

multiplatform-crypto-libsodium-bindings/src/jvmMain/kotlin/com/ionspin/kotlin/crypto/kdf/Kdf.kt

@@ -0,0 +1,49 @@
+package com.ionspin.kotlin.crypto.kdf
+
+import com.ionspin.kotlin.crypto.LibsodiumInitializer.sodium
+
+actual object Kdf {
+    /**
+     * The crypto_kdf_derive_from_key() function derives a subkey_id-th subkey subkey of length subkey_len bytes using
+     * the master key key and the context ctx.
+     * subkey_id can be any value up to (2^64)-1.
+     * subkey_len has to be between crypto_kdf_BYTES_MIN (inclusive) and crypto_kdf_BYTES_MAX (inclusive).
+     * Similar to a type, the context ctx is a 8 characters string describing what the key is going to be used for.
+     * Its purpose is to mitigate accidental bugs by separating domains. The same function used with the same key but
+     * in two distinct contexts is likely to generate two different outputs.
+     * Contexts don't have to be secret and can have a low entropy.
+     * Examples of contexts include UserName, __auth__, pictures and userdata.
+     * They must be crypto_kdf_CONTEXTBYTES bytes long.
+     * If more convenient, it is also fine to use a single global context for a whole application. This will still
+     * prevent the same keys from being mistakenly used by another application.
+     */
+    actual fun deriveFromKey(
+        subkeyId: Int,
+        subkeyLength: Int,
+        context: String,
+        masterKey: UByteArray
+    ): UByteArray {
+        val subkey = UByteArray(subkeyLength)
+        val contextEncoded = context.encodeToByteArray()
+
+        sodium.crypto_kdf_derive_from_key(
+            subkey.asByteArray(),
+            subkeyLength,
+            subkeyId.toLong(),
+            contextEncoded,
+            masterKey.asByteArray()
+        )
+
+        return subkey
+    }
+
+    /**
+     * The crypto_kdf_keygen() function creates a master key.
+     */
+    actual fun keygen(): UByteArray {
+        val masterKey = UByteArray(crypto_kdf_KEYBYTES)
+        sodium.crypto_kdf_keygen(masterKey.asByteArray())
+        return masterKey
+    }
+
+}

multiplatform-crypto-libsodium-bindings/src/nativeMain/kotlin/com/ionspin/kotlin/crypto/kdf/Kdf.kt

@@ -0,0 +1,66 @@
+package com.ionspin.kotlin.crypto.kdf
+
+import com.ionspin.kotlin.crypto.util.encodeToUByteArray
+import com.ionspin.kotlin.crypto.util.toPtr
+import kotlinx.cinterop.addressOf
+import kotlinx.cinterop.convert
+import kotlinx.cinterop.pin
+import libsodium.crypto_kdf_derive_from_key
+import libsodium.crypto_kdf_keygen
+
+actual object Kdf {
+    /**
+     * The crypto_kdf_derive_from_key() function derives a subkey_id-th subkey subkey of length subkey_len bytes using
+     * the master key key and the context ctx.
+     * subkey_id can be any value up to (2^64)-1.
+     * subkey_len has to be between crypto_kdf_BYTES_MIN (inclusive) and crypto_kdf_BYTES_MAX (inclusive).
+     * Similar to a type, the context ctx is a 8 characters string describing what the key is going to be used for.
+     * Its purpose is to mitigate accidental bugs by separating domains. The same function used with the same key but
+     * in two distinct contexts is likely to generate two different outputs.
+     * Contexts don't have to be secret and can have a low entropy.
+     * Examples of contexts include UserName, __auth__, pictures and userdata.
+     * They must be crypto_kdf_CONTEXTBYTES bytes long.
+     * If more convenient, it is also fine to use a single global context for a whole application. This will still
+     * prevent the same keys from being mistakenly used by another application.
+     */
+    actual fun deriveFromKey(
+        subkeyId: Int,
+        subkeyLength: Int,
+        context: String,
+        masterKey: UByteArray
+    ): UByteArray {
+        val subkey = UByteArray(subkeyLength)
+        val contextEncoded = context.encodeToByteArray()
+
+        val contextEncodedAndPinned = contextEncoded.pin()
+        val masterKeyPinned = masterKey.pin()
+        val subkeyPinned = subkey.pin()
+        crypto_kdf_derive_from_key(
+            subkeyPinned.toPtr(),
+            subkeyLength.convert(),
+            subkeyId.convert(),
+            contextEncodedAndPinned.addressOf(0),
+            masterKeyPinned.toPtr()
+        )
+
+        contextEncodedAndPinned.unpin()
+        masterKeyPinned.unpin()
+        subkeyPinned.unpin()
+
+        return subkey
+
+
+    }
+
+    /**
+     * The crypto_kdf_keygen() function creates a master key.
+     */
+    actual fun keygen(): UByteArray {
+        val masterKey = UByteArray(crypto_kdf_KEYBYTES)
+        val masterKeyPinned = masterKey.pin()
+        crypto_kdf_keygen(masterKeyPinned.toPtr())
+        masterKeyPinned.unpin()
+        return masterKey
+    }
+
+}