Do poly1305 with absolutely no modulo operators

ChaCha20_Poly1305_64/sim/modulo_theory.py

@@ -50,6 +50,18 @@ def modulo_theory_full(loops: int):
             print(f"{mod_sum=}")
             print(f"{mod_conventional=}")
 
+def friendly_modular_mult(value_a: int, value_b: int) -> int:
+    a_partials = [(value_a >> 26*i) & (2**26-1) for i in range(5)]
+
+    prods = [a_partial * value_b for a_partial in a_partials]
+
+    mods = [friendly_modulo(prod, 26*i) for i, prod in enumerate(prods)]
+
+
+    mod_sum = friendly_modulo(sum(mods), 0)
+
+    return mod_sum
+
 def friendly_modulo(val: int, shift_amount: int) -> int:
     high_part = val >> (130-shift_amount)
     low_part = (val << shift_amount) & (2**130-1)