passwords - What should be used as a salt? - Information
https://security.stackexchange.com/questions/8015/what-should-be-used-as-a-salt
The next most secure option is to use the username as the salt, in other words using 'md5 (username.password)'. Again, this defeats the standard rainbow table, but a hacker might generate a rainbow table for a specific username (like "root" or "administrator"), so that every time the password is changed, the hacker can do a looking in a rainbow ...
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