I pushed this to avoid the implication that DoD 5220 is still the
current standard describing the erasure of data from disk, or that it
is the most secure. NIST SP 800-88 Rev. 1 § 2.4 says the following
[1]:
For storage devices containing magnetic media, a single overwrite
pass with a fixed pattern such as binary zeros typically hinders
recovery of data even if state of the art laboratory techniques
are applied to attempt to retrieve the data.
Followed by warnings that this doesn't apply to non-magnetic media
types. That standard has since been withdrawn and replaced with Rev.
2, which has a similar claim in § 3.1.1, but without specifying the
number of overwrites:
Overwriting typically hinders the recovery of data even if
state-of-the-art laboratory techniques are applied to attempt to
retrieve the data.
Likewise, this is followed by warnings about not applying to
non-magnetic media types. It mentions in a footnote that the DoD
5220.22 overwrite passes were removed from documents in 2006, and does
not suggest any patterns or number of passes in its place.
I've left it in TODO because further research might justify changes to
'shred'. However, at the moment, it isn't clear to me that more than a
single pass has any benefit.
[1] https://csrc.nist.gov/pubs/sp/800/88/r1/final
[2] https://csrc.nist.gov/pubs/sp/800/88/r2/final
-- 8< --
* TODO: Mention that the referenced overwriting technique was removed
from NISPOM in 2006, and that it warns against overwriting for some
storage medias.
---
TODO | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/TODO b/TODO
index 02c7e63b2..9722b2ffe 100644
--- a/TODO
+++ b/TODO
@@ -69,8 +69,19 @@ 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:
-https://lists.gnu.org/r/bug-coreutils/2007-05/msg00075.html
+shred: Update shred as described here to conform to DoD 5220 rules.
+
+ This idea was originally proposed on the mailing list here:
+
+ https://lists.gnu.org/r/bug-coreutils/2007-05/msg00075.html
+
+ Note that the DoD removed the overwriting specifications from the
+ National Industrial Security Program Operating Manual in 2006. NIST
+ SP 800-88 Rev. 2, published in September 2025, warns that this method
+ should be avoided on some storage media, e.g., SSDs with
+ overprovisioning, where overwriting offers very little confidentiality
+ protection. NIST SP 800-88 Rev. 2 does not prescribe a specific
+ pattern or number of passes.
Remove suspicious uses of alloca (ones that may allocate more than
about 4k)
--
2.56.0
