Re: Default number of overwrites in shred

[Pádraig Brady]

Jim Meyering wrote:
> Sure.
> Too many people waste too much time with the existing defaults.

Pushing the attached soon so.

Note the recent paper suggesting a single pass is fine is:
http://sansforensics.wordpress.com/2009/01/15/overwriting-hard-drive-data/
However the methods there a questioned in the "Further Epilogue" here:
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

cheers,
Pádraig.

>From fdcda77f8cf05da18752e3c1e28ac59f819266b2 Mon Sep 17 00:00:00 2001
From: =?utf-8?q?P=C3=A1draig=20Brady?= <address@hidden>
Date: Thu, 22 Jan 2009 13:09:44 +0000
Subject: [PATCH] shred: change default number of overwrite from 25 to 3

* src/shred.c: Overwriting 3 times is sufficient
with current drive technologies.
* src/TODO: Reference Paul Eggert's suggestion
of enhancing shred to conform to DoD 5220 rules.
---
 TODO        |    3 +++
 src/shred.c |    2 +-
 2 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/TODO b/TODO
index cc5b0b3..c630548 100644
--- a/TODO
+++ b/TODO
@@ -107,6 +107,9 @@ sort: Investigate better sorting algorithms; see Knuth vol. 
3.
   5.3.1, who credits Lester Ford, Jr. and Selmer Johnson, American
   Mathematical Monthly 66 (1959), 387-389.
 
+shred: Update shred as described here to conform to DoD 5220 rules:
+http://lists.gnu.org/archive/html/bug-coreutils/2007-05/msg00075.html
+
 Remove suspicious uses of alloca (ones that may allocate more than
    about 4k)
 
diff --git a/src/shred.c b/src/shred.c
index 224f671..6ed4daa 100644
--- a/src/shred.c
+++ b/src/shred.c
@@ -102,7 +102,7 @@
 #include "randread.h"
 
 /* Default number of times to overwrite.  */
-enum { DEFAULT_PASSES = 25 };
+enum { DEFAULT_PASSES = 3 };
 
 /* How many seconds to wait before checking whether to output another
    verbose output line.  */
-- 
1.5.3.6