feat(x25519): add x25519 implementation for ios, macos (#80)

base-asymmetric-encryption/src/iosMain/kotlin/io/iohk/atala/prism/apollo/utils/KMMX25519KeyPair.kt

@@ -4,13 +4,10 @@ actual class KMMX25519KeyPair actual constructor(
     actual val privateKey: KMMX25519PrivateKey,
     actual val publicKey: KMMX25519PublicKey
 ) {
-    init {
-        throw NotImplementedError("X25519 is yet to be implemented in iOS")
-    }
-
     actual companion object : X25519KeyPairGeneration {
         override fun generateX25519KeyPair(): KMMX25519KeyPair {
-            throw NotImplementedError("X25519 is yet to be implemented in iOS")
+            val privateKey = KMMX25519PrivateKey()
+            return KMMX25519KeyPair(privateKey, privateKey.publicKey())
         }
     }
 }

base-asymmetric-encryption/src/iosMain/kotlin/io/iohk/atala/prism/apollo/utils/KMMX25519PrivateKey.kt

@@ -1,7 +1,32 @@
 package io.iohk.atala.prism.apollo.utils
 
+import cocoapods.IOHKCryptoKit.X25519
+import kotlinx.cinterop.ObjCObjectVar
+import kotlinx.cinterop.alloc
+import kotlinx.cinterop.memScoped
+import kotlinx.cinterop.ptr
+import kotlinx.cinterop.value
+import platform.Foundation.NSError
+
 actual class KMMX25519PrivateKey {
-    init {
-        throw NotImplementedError("X25519 is yet to be implemented in iOS")
+    public val raw: ByteArray
+
+    constructor(raw: ByteArray) {
+        this.raw = raw
+    }
+
+    constructor() {
+        this.raw = X25519.createPrivateKey().toByteArray()
+    }
+
+    @Throws(RuntimeException::class)
+    public fun publicKey(): KMMX25519PublicKey {
+        memScoped {
+            val errorRef = alloc<ObjCObjectVar<NSError?>>()
+            val result = X25519.publicKeyWithPrivateKey(raw.toNSData(), errorRef.ptr)
+            errorRef.value?.let { throw RuntimeException(it.localizedDescription()) }
+            val publicRaw = result?.toByteArray() ?: throw RuntimeException("Null result")
+            return KMMX25519PublicKey(publicRaw)
+        }
     }
 }

base-asymmetric-encryption/src/iosMain/kotlin/io/iohk/atala/prism/apollo/utils/KMMX25519PublicKey.kt

@@ -1,7 +1,9 @@
 package io.iohk.atala.prism.apollo.utils
 
 actual class KMMX25519PublicKey {
-    init {
-        throw NotImplementedError("X25519 is yet to be implemented in iOS")
+    public val raw: ByteArray
+
+    constructor(raw: ByteArray) {
+        this.raw = raw
     }
 }