It think you're confusing when to apply the advice to use the whole password. You don't use the plaintext password to create a salt when encrypting the password. You give the crypt function the whole encrypted password, salt and hashed password together as appears in the file, as the salt when authenticating a freshly entered plaintext password. This allows the crypt function to pull out as many bytes for the salt as the native crypt uses, whether that be the two for DES or some longer value. The rest is generally simply discarded by the crypt function. This way, you can write password authentication code which will work so long as the algortihm being used for authentication is the same as the one used for password creation and the two use the same interface. There's no need this way for the application to know beforehand how many bytes need to be given for the salt.

That being said, let me repeat that when generating the salt, the plaintext password should play absolutely no role.

Chris
911

In reply to Re: Re: Re: What's the idea of different salts in crypt()? by mr_mischief
in thread What's the idea of different salts in crypt()? by jeorgen

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