Every week brings stories of a new software exploit or corporate data breach in which user names and passwords are stolen. Security “experts” are advising us to make ever longer and more complex softwoods and to use unique passwords for each site that we visit. Why is this good advice and how do we go about making good but usable passwords? And how do we remember them all? I’ll attempt to answer these questions in this article in a way that is accessible to my retired buddies and family.

Why a User Name

There are lots of reasons to have a user name and password at sites that you visit regularly. Some benefit you while others benefit the site operator in a way that allows them to continue to provide the site’s service to you.

The site can provide personalized service
Some services are provided only to authenticated users having a standing business relationship with the organization (like your bank)
The site accumulates information that allows it to provide better services to you.

Some of these things can be done with or without an E-mail address using your home’s IP address as a substitute. Without an account, the site has no way of knowing which of several users at an address is actually visiting: you, your spouse, your 13 year old son? Without a sign-in, the site has to make somewhat general decisions about what to show you.

Why a Unique Password?

A password is a secret shared between you and the web site. When the user name and password pair are unique to the site, successful presentation of the user name and the associated password verifies you to the site and the site to you. You’ve shared that particular secret with only one web site. You each know that the intended party is at the other end of the line.

If login fails, you may have miss-typed the URL. Double check the URL before doing missing password procedures. It is not uncommon for unscrupulous operators to attempt to collect user name and password pairs by impersonating a site on a common misspelling of the URL.

Why a “Complex” Password?

The primary reason to use a complex password is to avoid well-known passwords or passwords composed from information known about you that an impersonator can obtain. This basically prevents an unscrupulous unskilled individual from committing theft of service or tampering with your relationship with the various sites that you visit. It is not intended to protect you from an organized and systematic attack.

Intelligence agencies and criminal syndicates make sophisticated attacks to break into web sites. One thing they try is to use statistically common passwords like “password12”. And surprisingly, they can make all the mess-ups like “pa$$word12”, “pas$word12”, etc. Most sites attempt to protect accounts against password guessing using several techniques.

Limiting the number of failed log in attempts in a time period
Increasing the delay between log in opportunities
Locking the account and requiring use of lost password procedures which involve different shared secrets.

How Passwords are Stored

Reputable web sites do not store your password. Rather they store the results of operating on your user name and password and possibly some well-known (to the site, anyway) other stuff to compute a hashed value. The addition of other stuff is called salting the hash or just salt for short. A hash function is a function that maps a string of data into another pseudo-random string. It is easy to compute the hash but prohibitively expensive or impossible to retrieve the original string from the hash because the hash function makes a many to 1 mapping. The hash is useful because the inputs that map to a given output are wildly different. No recognizable variation of the input string will give the same result as the correct string .

As a result, Google can not tell you your G-mail password. Google only has the hash. It is likely that the hash input and hash algorithm are designed to give different results when a common password is used with multiple Google accounts. Compromise of one account does not imply compromise of other accounts. Others may not be so clever or careful as Google.

What is taken in a break-in?

In many break-ins, the attackers gain the password database which is basically a list of user names with their hashed passwords. Many sites, especially entertainment sites, use a well known authentication process. Each such site produces the same hashed value from your E-mail address and password.

It is common for attackers to sell lists of user name password hash pairs. Today it is possible to break the hash to recover the original password. In other cases, the password list is stored in the clear and lists of user names with passwords are also available. Availability of these lists allow others to compromise your account to steal from you or to impersonate you.

What do I do?

To limit the consequences of password compromise and to authenticate my bank and broker’s web sites, I do the following.

I use unique passwords for each site
I use a password manager to store all my passwords
I use a password manager that syncs password data among computer, phone, and tablet
I chose the password manager carefully.

Making Unique Passwords

It is hard to make up good passwords. Choosing words myself generally results in using words associated with me, my interests, or my experiences. They’re not really random. Same with numbers. They’re usually the last 4 of an ancient phone number.

Instead, I use dice ware to make good but easy to type passwords whose parts are chosen randomly. Dice ware is a word list used with a dice cup and 5 dice. Do use real dice as computer random number generators are “pseudo-random”. That is, started with a seed, the random number generator will always make the same sequence of numbers. Which is to say, that they’re not random, they only appear to be. You can’t guess the next one given this one but you can reset the seed and recreate the sequence.

For web sites, I use three rolls to pick two strings (usually words) and a number. Each roll has 6 to the 5th power outcomes that are independent so there are 6 to the 15th power outcomes. Two rolls select a word from the word list. The advantage of the dice ware technique is that two words and a number stick in short term memory long enough to allow them to be typed easily yet the search space is big and fairly random. And you will come to remember those you use frequently. And there is nothing about the passwords that suggests you are using dice ware to make them. The dice ware word lists are available for a number of languages in addition to English that use the Latin alphabet.

Most sites will hold a password made this way. The troublesome sites are those that have a high complexity requirement but short string length. It is difficult to produce easily remembered 8 character passwords that have 2 digits, 2 punctuation, and one or more caps. You’re down to 4 letter words or going random. Also troublesome are sites that don’t tell you the maximum password length. These sites are truncating your password so the numbers, caps and special characters can be lost if they’re near the end.

Remembering 200 Passwords

I can’t do it. I don’t think computer security expert and ace cryptographer Bruce Schneirer can do it. So I use the OS X/IOS built in password manager and commercial product 1Password. The built in pass word manager works in the web browser and stores passwords in the OS X key chain. It can also store your SSH keys (for geeks) as of Mavericks and is synchronized via iCloud as of IOS 7.

I keep everything in 1Password also because I can use 1Password to keep track of security questions and responses and other information about the site and my relationship with the site that Key Chain will not store. As of IOS 8, applications will be able to ask 1Password for data. Agile Bits explains this interface and the actions they’ve taken to prevent misuse in their blog.

1Password never gives anything up without you authenticating using your 1Password master pass phrase. I have a good one that I can remember that I made using Dice Ware. It is guess proof.

The folks at 1Password understand cryptography and know how to build secure cryptographic applications. All 1Password data is protected using AES256 encryption and care is taken that the plain text and cypher text are not left lying around in memory.