Add export_key method to Aes256Encryption

src/crypto.rs

@@ -254,6 +254,10 @@ impl Aes256Encryption {
         })
     }
 
+    pub fn export_key(&self) -> [u8;32] {
+        self.aes_key
+    }
+
     pub fn encrypt_with_aes_key(&self) -> Result<CipherText> {
         match self.purpose {
             Purpose::Login => self.encrypt_login(),