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AESEncryptDecrypt.kt

@@ -0,0 +1,75 @@
+
+fun encrypt(context:Context, strToEncrypt: String): ByteArray {
+    val plainText = strToEncrypt.toByteArray(Charsets.UTF_8)
+    val keygen = KeyGenerator.getInstance("AES")
+    keygen.init(256)
+    val key = keygen.generateKey()
+    saveSecretKey(context, key)
+    val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
+    cipher.init(Cipher.ENCRYPT_MODE, key)
+    val cipherText = cipher.doFinal(plainText)
+    saveInitializationVector(context, cipher.iv)
+
+    val sb = StringBuilder()
+    for (b in cipherText) {
+        sb.append(b.toChar())
+    }
+    Toast.makeText(context, "dbg encrypted = [" + sb.toString() + "]", Toast.LENGTH_LONG).show()
+
+    return cipherText
+}
+
+fun decrypt(context:Context, dataToDecrypt: ByteArray): ByteArray {
+    val cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING")
+    val ivSpec = IvParameterSpec(getSavedInitializationVector(context))
+    cipher.init(Cipher.DECRYPT_MODE, getSavedSecretKey(context), ivSpec)
+    val cipherText = cipher.doFinal(dataToDecrypt)
+
+    val sb = StringBuilder()
+    for (b in cipherText) {
+        sb.append(b.toChar())
+    }
+    Toast.makeText(context, "dbg decrypted = [" + sb.toString() + "]", Toast.LENGTH_LONG).show()
+
+    return cipherText
+}
+
+fun saveSecretKey(context:Context, secretKey: SecretKey) {
+    val baos = ByteArrayOutputStream()
+    val oos = ObjectOutputStream(baos)
+    oos.writeObject(secretKey)
+    val strToSave = String(android.util.Base64.encode(baos.toByteArray(), android.util.Base64.DEFAULT))
+    val sharedPref = PreferenceManager.getDefaultSharedPreferences(context)
+    val editor = sharedPref.edit()
+    editor.putString("secret_key", strToSave)
+    editor.apply()
+}
+
+fun getSavedSecretKey(context: Context): SecretKey {
+    val sharedPref = PreferenceManager.getDefaultSharedPreferences(context)
+    val strSecretKey = sharedPref.getString("secret_key", "")
+    val bytes = android.util.Base64.decode(strSecretKey, android.util.Base64.DEFAULT)
+    val ois = ObjectInputStream(ByteArrayInputStream(bytes))
+    val secretKey = ois.readObject() as SecretKey
+    return secretKey
+}
+
+fun saveInitializationVector(context: Context, initializationVector: ByteArray) {
+    val baos = ByteArrayOutputStream()
+    val oos = ObjectOutputStream(baos)
+    oos.writeObject(initializationVector)
+    val strToSave = String(android.util.Base64.encode(baos.toByteArray(), android.util.Base64.DEFAULT))
+    val sharedPref = PreferenceManager.getDefaultSharedPreferences(context)
+    val editor = sharedPref.edit()
+    editor.putString("initialization_vector", strToSave)
+    editor.apply()
+}
+
+fun getSavedInitializationVector(context: Context) : ByteArray {
+    val sharedPref = PreferenceManager.getDefaultSharedPreferences(context)
+    val strInitializationVector = sharedPref.getString("initialization_vector", "")
+    val bytes = android.util.Base64.decode(strInitializationVector, android.util.Base64.DEFAULT)
+    val ois = ObjectInputStream(ByteArrayInputStream(bytes))
+    val initializationVector = ois.readObject() as ByteArray
+    return initializationVector
+}