X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/tripe/blobdiff_plain/1f531e36b1fdead11744519d90c9bbff32d12e41..d132c65168871d21ad93f2aa96d79fa6223c9943:/keyset.c

diff --git a/keyset.c b/keyset.c
index cf041499..27341c00 100644
--- 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 */