/usr/share/doc/samhain/manual.html/hash-function.html

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>Available checksum functions</TITLE
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NAME="HASH-FUNCTION"
>5.2. Available checksum functions</A
></H1
><P
>  A cryptographic hash function is a one-way function 
  <B
CLASS="COMMAND"
>H(<TT
CLASS="REPLACEABLE"
><I
>foo</I
></TT
>)</B
> such
  that it is easy to compute 
  <B
CLASS="COMMAND"
>H(<TT
CLASS="REPLACEABLE"
><I
>foo</I
></TT
>)</B
> from 
  <TT
CLASS="REPLACEABLE"
><I
>foo</I
></TT
>, but 
  infeasible to compute <TT
CLASS="REPLACEABLE"
><I
>foo</I
></TT
>
  from <B
CLASS="COMMAND"
>H(<TT
CLASS="REPLACEABLE"
><I
>foo</I
></TT
>)</B
>, or
  to find <TT
CLASS="REPLACEABLE"
><I
>bar</I
></TT
> such that 
  <B
CLASS="COMMAND"
>H(<TT
CLASS="REPLACEABLE"
><I
>bar</I
></TT
>)</B
> = 
  <B
CLASS="COMMAND"
>H(<TT
CLASS="REPLACEABLE"
><I
>foo</I
></TT
>)</B
> (which would allow
  to replace <TT
CLASS="REPLACEABLE"
><I
>foo</I
></TT
> with 
  <TT
CLASS="REPLACEABLE"
><I
>bar</I
></TT
> without changing the hash function).</P
><P
>  One common usage of a such a hash function is the 
  computation of <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>checksums</I
></SPAN
> 
  of files, such that any modification of a file can be noticed, 
  as its checksum will change. </P
><P
>  For computing checksums of files, and also for some other purposes, 
  <SPAN
CLASS="APPLICATION"
>samhain</SPAN
> uses the TIGER hash function 
  developed by Ross Anderson
  and Eli Biham. The output of this function is 192 bits long, and the
  function can be implemented efficiently on 32-bit and 64-bit machines.
  Technical details can be found at 
  <A
HREF="http://www.cs.technion.ac.il/~biham/Reports/Tiger/"
TARGET="_top"
>this
page</A
>.</P
><P
>  As of version 1.2.10, also the MD5 and SHA-1 hash functions are available.
  (You need to set the option <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>DigestAlgo=MD5</I
></SPAN
> or 
  <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>DigestAlgo=SHA1</I
></SPAN
> in the config file to enable this).
  Note that MD5 is somewhat faster, but because of security concerns
  it is not recommended anymore for new applications.</P
><P
>  As of version 3.1.0, also the SHA2-256 hash function is available.
  (You need to set the option <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>DigestAlgo=SHA256</I
></SPAN
> 
  in the config file to enable this).</P
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samhain 3.1.0-7build1 / usr / share / doc / samhain / manual.html / hash-function.html
