[qmc] feat: add helper method to create QMCv2 Decipher from EKey

um_crypto/qmc/src/lib.rs

@@ -35,6 +35,11 @@ impl QMCv2Cipher {
         Ok(cipher)
     }
 
+    pub fn new_from_ekey<T: AsRef<[u8]>>(ekey_str: T) -> Result<Self> {
+        let key = ekey::decrypt(ekey_str)?;
+        Self::new(key)
+    }
+
     pub fn decrypt<T>(&self, data: &mut T, offset: usize)
     where
         T: AsMut<[u8]> + ?Sized,