diff --git a/pySim/esim/saip/param_source.py b/pySim/esim/saip/param_source.py
index 8c0078d7..7690ca99 100644
--- a/pySim/esim/saip/param_source.py
+++ b/pySim/esim/saip/param_source.py
@@ -124,15 +124,18 @@ class DecimalRangeSource(InputExpandingParamSource):
         last_value = int(last_str if last_str is not None else "9" * len(first_str))
         return cls(num_digits=len(first_str), first_value=first_value, last_value=last_value)
 
-class RandomDigitSource(DecimalRangeSource):
+class RandomSourceMixin:
+    random_impl = random # TODO secure random source?
+
+class RandomDigitSource(DecimalRangeSource, RandomSourceMixin):
     """return a different sequence of random decimal digits each"""
     name = "random decimal digits"
 
     def get_next(self, csv_row:dict=None):
-        val = random.randint(*self.val_first_last) # TODO secure random source?
+        val = self.random_impl.randint(*self.val_first_last)
         return self.val_to_digit(val)
 
-class RandomHexDigitSource(InputExpandingParamSource):
+class RandomHexDigitSource(InputExpandingParamSource, RandomSourceMixin):
     """return a different sequence of random hexadecimal digits each"""
     name = "random hexadecimal digits"
 
@@ -147,7 +150,7 @@ class RandomHexDigitSource(InputExpandingParamSource):
         self.num_digits = num_digits
 
     def get_next(self, csv_row:dict=None):
-        val = random.randbytes(self.num_digits // 2) # TODO secure random source?
+        val = self.random_impl.randbytes(self.num_digits // 2)
         return b2h(val)
 
     @classmethod