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Strengthen some of the language concerning attacks on MD5, in light of the

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recent demonstration of a forged SSL certificate.  Add text pointing out
that SHA-1 is at least theoretically broken.  Add a recommendation that
new applications use SHA-256.

MFC after:	1 month
This commit is contained in:
Colin Percival 2009-01-06 19:25:24 +00:00
parent 853e670bb4
commit 4c55b9e02e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=186836
1 changed files with 16 additions and 8 deletions
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sbin/md5/md5.1
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@ -49,15 +49,23 @@ key under a public-key cryptosystem such as
.Tn RSA .
.Pp
.Tn MD5
has not yet (2007-03-05) been broken, but sufficient attacks have been
made that its security is in some doubt.
The attacks on
has been completely broken as far as finding collisions is
concerned, and should not be relied upon to produce unique outputs.
This also means that
.Tn MD5
are in the nature of finding
.Dq collisions
\(em that is, multiple
inputs which hash to the same value; it is still unlikely for an attacker
to be able to determine the exact original input given a hash value.
should not be used as part of a cryptographic signature scheme.
At the current time (2009-01-06) there is no publicly known method to
"reverse" MD5, i.e., to find an input given a hash value.
.Pp
.Tn SHA-1
currently (2009-01-06) has no known collisions, but an attack has been
found which is faster than a brute-force search, placing the security of
.Tn SHA-1
in doubt.
.Pp
It is recommended that all new applications use
.Tn SHA-256
instead of one of the other hash functions.
.Pp
The following options may be used in any combination and must
precede any files named on the command line.