On 22/08/2010 00:48, Tom Del Rosso wrote:
> Rod Speed wrote:
>> Tom Del Rosso wrote
>>> Bob I wrote
>>
>>>> The password and account ARE secure, you won't be accessing the
>>>> account's encrypted files with a changed or flattened password.
>>
>>> So it puts the new password somewhere else?
>>
>> Nope, it puts it in the same place, but encryption is a completely
>> different process to decryption.
>> In fact when checking whether the password has been entered correctly
>> when say logging on, the password entered is encrypted and the encrypted
>> form is
>> compared with the stored encrypted form of the original password and if
>> they match, the
>> password is correct. Thats nothing like decrypting the stored form of the
>> original password.
>>
>> In fact it isnt even possible to reverse some forms of encryption at
>> all, they are one way encryptions.
>
> Thanks. That's it then. I'm aware that there are non-reversible
> encryptions, but I didn't consider that possible, because years ago I used
> another password cracker (fee-based, from a commercial operation) to recover
> a password from a Win2k system. It required copying the sam file and
> emailing it to them. I guess they did it by brute force, until they found a
> password that created the same encrypted data. I had always assumed they
> decrypted it.
>
Yes, these things are done by trial and error. Often such a company
will have large "rainbow" tables - they take tables of likely passwords
(such as common kids names, common pet names, misspellings of
"password", birthdays, etc.), dictionaries, etc., and run each one
through the password encryption algorithm. Then "cracking" the password
is as simple as looking it up in this table. If they get a match, they
have the original password. If not, then they need to run through
exhaustive searches.
If you ever have to break into a windows system again, it is a lot
easier to use a windows password reset live CD. These don't make any
attempt to identify the old password, but simply replace it with a known
(blank) one. It's a lot faster and cheaper than an external company.
If you actually need to recover the password rather than just change it
to something you know, there are again free tools for that.