Devai Tamas pointed out on the mailing list that random_prime with bits

set to 2, 3, or 4 was not returning a random prime due to reducing the
rng output modulo 1 instead of mod 2 in choosing which prime of that size
to return. Oops.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/math/numbertheory/make_prm.cpp b/src/math/numbertheory/make_prm.cpp
index 226f0c38f..b136b6d25 100644
--- a/src/math/numbertheory/make_prm.cpp
+++ b/src/math/numbertheory/make_prm.cpp
@@ -22,11 +22,11 @@ BigInt random_prime(RandomNumberGenerator& rng,
       throw Invalid_Argument("random_prime: Can't make a prime of " +
                              to_string(bits) + " bits");
    else if(bits == 2)
-      return ((rng.next_byte() % 1) ? 2 : 3);
+      return ((rng.next_byte() % 2) ? 2 : 3);
    else if(bits == 3)
-      return ((rng.next_byte() % 1) ? 5 : 7);
+      return ((rng.next_byte() % 2) ? 5 : 7);
    else if(bits == 4)
-      return ((rng.next_byte() % 1) ? 11 : 13);
+      return ((rng.next_byte() % 2) ? 11 : 13);
 
    if(coprime <= 0)
       throw Invalid_Argument("random_prime: coprime must be > 0");