Fix FPE decryption; off by one in the round numbers

1 files changed, 2 insertions, 2 deletions

diff --git a/src/fpe/fpe.cpp b/src/fpe/fpe.cpp
index b2dbf7eb1..e3be34ef0 100644
--- a/src/fpe/fpe.cpp
+++ b/src/fpe/fpe.cpp
@@ -156,8 +156,8 @@ BigInt fpe_decrypt(const BigInt& n, const BigInt& X0,
       BigInt W = X % a;
       BigInt R = X / a;
 
-      BigInt L = (W - F(r-i, R)) % a;
-      X = b*L + R;
+      BigInt L = (W - F(r-i-1, R)) % a;
+      X = b * L + R;
       }
 
    return X;