Re: Passwd Encryption (Re: Linux security)
On Wed, 19 Aug 1998, Chris wrote:
: On Tue, 18 Aug 1998, Steve Lamb wrote:
:
: > On Tue, 18 Aug 1998 23:27:40 -0500 (CDT), Nathan E Norman wrote:
: >
: > >No. The first two characters of the "Encrypted password" field are the
: > >"salt"; the plaintext password collected from loogin or wherever is
: > >crypted using that salt, and the result compared to the entire field.
: >
: > Hrm, guess things have changed since the other nutshell book was printed.
: > :/
: >
: >
:
:
: An extract from the crypt(3) man page:
:
:
: crypt is the password encryption function. It is based on
: the Data Encryption Standard algorithm with variations
: intended (among other things) to discourage use of hard
: ware implementations of a key search.
:
: key is a user's typed password.
:
: salt is a two-character string chosen from the set
: [a-zA-Z0-9./]. This string is used to perturb the algo
: rithm in one of 4096 different ways.
:
: By taking the lowest 7 bit of each character of the key, a
: 56-bit key is obtained. This 56-bit key is used to
: encrypt repeatedly a constant string (usually a string
: consisting of all zeros). The returned value points to
: the encrypted password, a series of 13 printable ASCII
: characters (the first two characters represent the salt
: itself). The return value points to static data whose
: content is overwritten by each call.
Ah! Ok, I see what I was missing.
--
Nathan Norman
MidcoNet 410 South Phillips Avenue Sioux Falls, SD
mailto:finn@midco.net http://www.midco.net
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