- Updated examples to use appropriate sizes for larger RSA keys (up to 16k)

diff --git a/programs/pkey/rsa_sign_pss.c b/programs/pkey/rsa_sign_pss.c
index c00c8d8..ffc5de0 100644
--- a/programs/pkey/rsa_sign_pss.c
+++ b/programs/pkey/rsa_sign_pss.c
@@ -67,7 +67,7 @@
     entropy_context entropy;
     ctr_drbg_context ctr_drbg;
     unsigned char hash[20];
-    unsigned char buf[512];
+    unsigned char buf[POLARSSL_MPI_MAX_SIZE];
     char filename[512];
     char *pers = "rsa_sign_pss";