diff --git a/src/shamira/fft.py b/src/shamira/fft.py
--- a/src/shamira/fft.py
+++ b/src/shamira/fft.py
@@ -1,6 +1,7 @@
 import math
 import cmath
 import itertools
+from functools import cache
 
 from .gf256 import gfmul, gfpow
 
@@ -20,6 +21,7 @@ def ceil_size(n):
 	return ni
 
 
+@cache
 def precompute_x(n):
 	"""Return a geometric sequence [1, w, w**2, ..., w**(n-1)], where w**n==1.
 	This can be done only for certain values of n."""