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-rw-r--r--shamir.py8
1 files changed, 4 insertions, 4 deletions
diff --git a/shamir.py b/shamir.py
index 808dfc5..60a4d78 100644
--- a/shamir.py
+++ b/shamir.py
@@ -51,10 +51,10 @@ def _lagrange_interpolate(x, x_s, y_s, p):
assert k == len(set(x_s)), "points must be distinct"
def prod(vals): # product of inputs
- accum = 1
+ r = 1
for v in vals:
- accum *= v
- return accum
+ r = (r * v) % p
+ return r
nums = [] # avoid inexact division
dens = []
for i in range(k):
@@ -65,7 +65,7 @@ def _lagrange_interpolate(x, x_s, y_s, p):
nums.append(prod(x - o for o in others)) # \Prod_{j \neq i}{(x - x_j)}
dens.append(prod(cur - o for o in others)) # \Prod_{j \neq i}{(x_i - x_j)}
den = prod(dens)
- num = sum([_divmod(nums[i] * den * y_s[i] % p, dens[i], p)
+ num = sum([_divmod((nums[i] * den * y_s[i]) % p, dens[i], p)
for i in range(k)])
return (_divmod(num, den, p) + p) % p