[Gzz-commits] manuscripts/Sigs article.rst poss.py

[Tuomas J. Lukka]

CVSROOT:        /cvsroot/gzz
Module name:    manuscripts
Changes by:     Tuomas J. Lukka <address@hidden>        03/05/18 15:47:11

Modified files:
        Sigs           : article.rst poss.py 

Log message:
        scheme

CVSWeb URLs:
http://savannah.gnu.org/cgi-bin/viewcvs/gzz/manuscripts/Sigs/article.rst.diff?tr1=1.93&tr2=1.94&r1=text&r2=text
http://savannah.gnu.org/cgi-bin/viewcvs/gzz/manuscripts/Sigs/poss.py.diff?tr1=1.6&tr2=1.7&r1=text&r2=text

Patches:
Index: manuscripts/Sigs/article.rst
diff -u manuscripts/Sigs/article.rst:1.93 manuscripts/Sigs/article.rst:1.94
--- manuscripts/Sigs/article.rst:1.93   Sun May 18 15:37:41 2003
+++ manuscripts/Sigs/article.rst        Sun May 18 15:47:11 2003
@@ -531,9 +531,14 @@
 
 ?
 
+<<<<<<< article.rst
+- serious vulnerabilities with chosen-message multiple signatures,
+
+=======
 Octuplet: `$(1, b, kh, th, h, t, 1, 1+k)$`
 
 
+>>>>>>> 1.93
 Bleichenbacher-Maurer
 ---------------------
 
@@ -611,7 +616,10 @@
 
   - biba:
 
-  - Reyzin subset-resilient; 
+  - Reyzin subset-resilient. The security requirement, 
+    for a single signature, means that 
+    `$\\log t \ge {160-\log k \over k}$`.
+    A suitable choise seems to be `$t=1024$`, `$k=24$`
 
   - alternatively, the Reyzin theoretical construction may be used,
     where the time spent is somewhat more but security depends
Index: manuscripts/Sigs/poss.py
diff -u manuscripts/Sigs/poss.py:1.6 manuscripts/Sigs/poss.py:1.7
--- manuscripts/Sigs/poss.py:1.6        Sun May 18 15:37:42 2003
+++ manuscripts/Sigs/poss.py    Sun May 18 15:47:11 2003
@@ -2,6 +2,12 @@
 import math
 from math import log, log10, ceil
 
+def fact(x):
+    return reduce(lambda a, b: a*b, range(1, x+1), 1L)
+
+def choose(n, k):
+    return fact(n) / (fact(k)*fact(n-k))
+
 def lamport(h, b):
     return (1, b, b*h, 2*b*h, h, 2*b, 0, b)