Decrypt Unix Password File
Jerome Tan <jti@i-manila.com.ph> writes:
How can I decrypt Unix password file?
If the /etc/passwd file does not use shadow passwords, then the second field of each line contains the 'salt' and a value dependent on both the salt and the secret password. One can try to compute the function of all reasonable dictionary words with the salts in the /etc/passwd file, and hope that some of them match the values listed in the file. There are many programs that do this, e.g., look for 'crack'. This attack can be made more difficult if you force your users not to use easy-to-guess passwords, and if you use something like NIS and shadowing to make the public part of the passwords harder to get. --- Dr.Dimitri Vulis KOTM Brighton Beach Boardwalk BBS, Forest Hills, N.Y.: +1-718-261-2013, 14.4Kbps
On Tue, 23 Jul 1996, Dr.Dimitri Vulis KOTM wrote:
Jerome Tan <jti@i-manila.com.ph> writes:
How can I decrypt Unix password file? There are many programs that do this, e.g., look for 'crack'. This attack can be made more difficult if you force your users not to use easy-to-guess passwords, and if you use something like NIS and shadowing to make the public part of the passwords harder to get.
From my conversations with Mr. Tan, he seems to be a high school bent of mischeif. He is the one who asked about penetating firewalls, and now wants to know how to hack a unix passwd file. Now, I am not philosophically opposed to hacking, unless you are doing it to a machine that I am responsible for, (in which case you'd better hope the FBI finds you before I do) but I don't think that it would be a good idea to just give him the information. He would wind up getting caught all too easily, and might point to this list as a source of information on cracking techniques. I don't know if this should go to the whole list, so you can bounce it there if you think it proper. Petro, Christopher C. petro@suba.com <prefered for any non-list stuff> snow@smoke.suba.com
On Tue, 23 Jul 1996, Dr.Dimitri Vulis KOTM wrote:
Jerome Tan <jti@i-manila.com.ph> writes:
How can I decrypt Unix password file? There are many programs that do this, e.g., look for 'crack'. This attack can be made more difficult if you force your users not to use easy-to-guess passwords, and if you use something like NIS and shadowing to make the public part of the passwords harder to get.
From my conversations with Mr. Tan, he seems to be a high school bent of mischeif. He is the one who asked about penetating firewalls, and now wants to know how to hack a unix passwd file.
Now, I am not philosophically opposed to hacking, unless you are doing it to a machine that I am responsible for, (in which case you'd better hope the FBI finds you before I do) but I don't think that it would be a good idea to just give him the information. He would wind up getting caught all too easily, and might point to this list as a source of information on cracking techniques.
Just what they want, anyway -- make cypherpunks look like villins.
I don't know if this should go to the whole list, so you can bounce it there if you think it proper.
I think you used your judgement well in this case. There are many places to start learning about firewalls and UNIX security. I recommend the _Building Internet Firewalls_ O'reilly book, as well as _Practical UNIX & Internet Security_ as well. I don't feel right about spoon feeding cracking info to someone like this. (PS: The animal on the _Building Internet Firewalls_ book is hidden behind the gates. It is a Trojan Horse. I heard this secondhand.)
Petro, Christopher C. petro@suba.com <prefered for any non-list stuff> snow@smoke.suba.com
-----BEGIN PGP SIGNED MESSAGE----- On Tue, 23 Jul 1996, Jerome Tan wrote:
How can I decrypt Unix password file?
You can't decrypt a password file. The password is hashed by using the password as a DES key, and encrypting a string of 8 NULs 25 times. The E-tables of the DES algorithm are permutated according to the twelve-bit salt which is encoded in the first two characters of the hashed password field. The E-tables are permutated by swapping the entries N and N+24 if the Nth bit of the salt value is 1. A salt value of 0 will result in straight DES being used 25 times. This is the only salt value that can't be used in the UNIX password file. A program like Crack will use a dictionary attack to crack a password file. It's available at ftp://ftp.funet.fi/pub/security. - -- Mark PGP encrypted mail prefered Key fingerprint = d61734f2800486ae6f79bfeb70f95348 http://www.voicenet.com/~markm/ -----BEGIN PGP SIGNATURE----- Version: 2.6.3 Charset: noconv iQCVAwUBMfT77bZc+sv5siulAQGPpwP/R93/3Z4o14CYeYNZOBa0kK7tArcDAP12 bWG1pw0pW0FZDbWg12LOz8xZbvAiSe88sNQhuzs8b8GwS71yzhGDwCMRFGjIealE xiUch7b6qnE9w9H7gV80nxcVTS/sRzEqYxjhT8JRU9YalS5CvzVo1ciTSj28xDs7 e62HYbBpTKI= =E0Wh -----END PGP SIGNATURE-----
participants (5)
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dlv＠bwalk.dm.com -
Douglas R. Floyd -
Jerome Tan -
Mark M. -
snow