diff --git a/phe/paillier.py b/phe/paillier.py
index ecda669..68e94fa 100644
--- a/phe/paillier.py
+++ b/phe/paillier.py
@@ -28,7 +28,10 @@
 from phe import EncodedNumber
 from phe.util import invert, powmod, getprimeover, isqrt
 
-DEFAULT_KEYSIZE = 2048
+# Paillier cryptosystem is based on integer factorisation.
+# The default is chosen to give a minimum of 128 bits of security.
+# https://www.keylength.com/en/4/
+DEFAULT_KEYSIZE = 3072
 
 
 def generate_paillier_keypair(private_keyring=None, n_length=DEFAULT_KEYSIZE):