Quantify collision probabilities for the stated data volume bounds.

diff --git a/keyset.c b/keyset.c
index cf04149..27341c0 100644 (file)
--- a/keyset.c
+++ b/keyset.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: keyset.c,v 1.3 2001/02/16 21:39:55 mdw Exp $
+ * $Id: keyset.c,v 1.4 2001/06/16 14:06:40 mdw Exp $
  *
  * Handling of symmetric keysets
  *
@@ -29,6 +29,9 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: keyset.c,v $
+ * Revision 1.4  2001/06/16 14:06:40  mdw
+ * Quantify collision probabilities for the stated data volume bounds.
+ *
  * Revision 1.3  2001/02/16 21:39:55  mdw
  * Major overhaul.  Separate functions for manipulating keysets from
  * functions for manipulating keyset lists.  Introduce a concept of
@@ -48,6 +51,13 @@
 
 /*----- Tunable parameters ------------------------------------------------*/
 
+/* --- Note on size limits --- *
+ *
+ * For a 64-bit block cipher (e.g., Blowfish), the probability of a collision
+ * occurring after 32 MB is less than %$2^{-21}$%, and the probability of a
+ * collision occurring after 64 MB is less than %$2^{-19}$%.
+ */
+
 #define T_EXP MIN(60)                  /* Expiry time for a key */
 #define T_REGEN MIN(45)                        /* Regeneration time for a key */
 #define SZ_EXP MEG(64)                 /* Expiry data size for a key */