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1. Introduction to password management

This introductory chapter will superficially cover password management issues and describe how this program addresses them.

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1.1 How evil-doers access your accounts

First and foremost, because people give them their credentials (user name and password). Not deliberately, of course. They leave them around or reply to a phishing scam or whatever. There’s nothing providers of security assistance can do about it. That’s the user’s responsibility. Be careful out there. Keep your systems clean of spyware and watch for phishers.

The next most common method is for a site to get “hacked” and the crooks make off with password files. Hopefully, they’ve been hash encoded, but they are sometimes in the clear. If they are hashed, then the crackers will try to reverse the hash and see how far and wide they can use your credentials.

Other possibilities are telescopes, line taps, wireless sniffing and so on. Unless you are a secret agent working on national security matters, these possibilities are not terribly likely possibilities.

The purpose of this software is to render useless, limit the potential damage, or, at least, make it difficult to gain much use out of any information captured. And, also, make it convenient enough to use that it is actually used. A very secure password scheme that is a nuisance to use, won’t be used, and is therefore not very useful.

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1.2 How to keep evil-doers at bay

First and foremost, make sure you know which web site you are interacting with when you supply credentials. Do not blindly click an email that looks like one from Pay Pal or your bank. Go to your financial institutions via a bookmark or a well-established link.

Next, use different passwords at different web sites. Unless you restrict yourself to very few web sites, this means you must manage them somehow. Pieces of paper get lost. Password list files can wind up getting compromised. If that happens, your entire online world is now open. Encrypted password list files can get decrypted, yielding the same possibility.

Do not use either words or common transformations of words for passwords. Such techniques severly limit possibilities and constrained possibilities are searched more quickly.

Use long passwords. The longer they are, the more difficult (compute costly) they are to break.

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1.3 How gnu-pw-mgr helps

Passwords must be long, not based on dictionary words, never repeated, and not recorded where they can be gotten at. You can’t do it by memory.

This program addresses the recording problem by not recording passwords. They get re-computed every time, based on two separate factors each of which is unlikely to come into the hands of miscreants. The first factor is a series of one or more password “seeds” or “salts”. You specify a tag for it and the seed itself is a block of text that contains at least 64 characters. The second factor is a transformation of the web site address. That transformation should be easy to remember, fairly easy to type, include odd capitalization, use multiple unusual punctuation characters, have a secret word or two and never, ever be written down.

The text, the URL transform and the tag get hashed together to construct the password. Since different web sites have different password requirements and allowances, the result is trimmed and tweaked until it meets the requirements. It is always possible that new requirements might pop up, and the password polishing code has been written to be extensible.

Using this program not only makes it simple to have different passwords for different web sites, it actually makes it inconvenient to use the same password. It does not support the same password, so you would have to remember the jumble of letters and numbers for any alternate web site. You won’t do that.

gnu-pw-mgr works by storing the seed in a private configuration file and obtaining the password identifier either from the command line or by reading it from standard input. This configuration file must be secured from reading and writing by other users, but obtaining access will not reveal passwords. The key to this is the password identifier. It is the second factor in the authentication (password re-creation) that is never recorded.

The configuration file does not need to be super secret. What needs to be super secret is the transformation used for constructing password identifiers. That transform includes a prefix, a suffix, alternate capitalizations and a variety of word separators. For example, you could prefix every domain name with “access” and suffix it with “por-favor”, then use an unusual spelling of the domain, perhaps “ExAmplE.moC”. This yields a password id of “access/ExAmplE+moC=por-favor”. You can remember that fairly easily. If a bad actor gets your seed file, they won’t work out the transform any time soon.

On the other hand, if someone does happen to see you create the transform, it will still do no good, unless they also get the second factor: the seed file. This is true even if they also get one password. There is no way to derive the seed file from the password id and the resulting password. It is a one way hash function. It is not an encryption.

Finally, since every site has their own set of attributes that make for acceptable passwords, the hash of the inputs must be modified. The hash of the password id by itself is used as a key to look up any previously established password constraints (see section password options). These password attributes are lentgh, character types required and/or prohibited from being in the password and some hint about your login name or id. That name need not be exactly your login name, just something that will remind you about which one you use for the site. It may be omitted, if you are sure you can remember.

These site specific options are then used to format the password display.

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This document was generated by Bruce Korb on November 14, 2013 using texi2html 1.82.