EncryptedKVStorage: can destroy exisint creating one with a new key

src/commonMain/kotlin/net/sergeych/crypto2/EncryptedKVStorage.kt

@@ -15,11 +15,19 @@ import kotlin.random.nextUBytes
  *
  * Keys are stored encrypted and used hashed so it is not possible to
  * retrieve them without knowing the encryption key.
+ *
+ * @param plainStore where to store encrypted data
+ * @param encryptionKey key to decrypt existing/encrypt new data. Can cause [DecryptionFailedException]
+ *          if the key is wrong and the storage is already initialized with a new key and same [prefix]
+ * @param prefix prefix for keys to distinguish from other data in [plainStore]
+ * @param removeExisting if true, removes all existing data in [plainStore] if the [encryptionKey] can't
+ *          decrypt existing encrypted data
  */
 class EncryptedKVStorage(
     private val plainStore: KVStorage,
     private var encryptionKey: SymmetricKey,
-    private val prefix: String = "EKVS_"
+    private val prefix: String = "EKVS_",
+    removeExisting: Boolean
 ) : KVStorage {
     private val op = ProtectedOp()
 
@@ -29,10 +37,21 @@ class EncryptedKVStorage(
 
     init {
         var encryptedSeed by plainStore.optStored<UByteArray>("$prefix#seed")
-        seed = encryptedSeed?.let { encryptionKey.decrypt(it) }
-            ?: Random.nextUBytes(32).also {
-                encryptedSeed = encryptionKey.encrypt(it)
-            }
+        seed = try {
+            encryptedSeed?.let { encryptionKey.decrypt(it) }
+                ?: Random.nextUBytes(32).also {
+                    encryptedSeed = encryptionKey.encrypt(it)
+                }
+        } catch (x: DecryptionFailedException) {
+            if (removeExisting) {
+                plainStore.keys.filter { it.startsWith(prefix) }.forEach {
+                    plainStore.delete(it)
+                }
+                Random.nextUBytes(32).also {
+                    encryptedSeed = encryptionKey.encrypt(it)
+                }
+            } else throw x
+        }
     }
 
     private fun mkkey(key: String): String =