Introduction to Passwords

Passwords are an essential part of our everyday digital lives. We use them to protect our accounts, our devices and our secrets. Despite often being the only thing between us and an adversary who's after our private information, not a lot of thought is put into them, which often leads to people using passwords that can be easily guessed or brute-forced.

Best Practices¶

Use unique passwords for every service¶

Imagine this; you sign up for an account with the same e-mail and password on multiple online services. If one of those service providers is malicious, or their service has a data breach that exposes your password in an unencrypted format, all a bad actor would have to do is try that e-mail and password combination across multiple popular services until they get a hit. It doesn't matter how strong that one password is, because they already have it.

This is called credential stuffing, and it is one of the most common ways that your accounts can be compromised by bad actors. To avoid this, make sure that you never re-use your passwords.

Use randomly generated passwords¶

You should never rely on yourself to come up with a good password. We recommend using randomly generated passwords or diceware passphrases with sufficient entropy to protect your accounts and devices.

All of our recommended password managers include a built-in password generator that you can use.

Rotating Passwords¶

You should avoid changing passwords that you have to remember (such as your password manager's master password) too often unless you have reason to believe it has been compromised, as changing it too often exposes you to the risk of forgetting it.

When it comes to passwords that you don't have to remember (such as passwords stored inside your password manager), if your threat model calls for it, we recommend going through important accounts (especially accounts that don't use multi-factor authentication) and changing their password every couple of months, in case they have been compromised in a data breach that hasn't become public yet. Most password managers allow you to set an expiry date for your password to make this easier to manage.

Checking for data breaches

If your password manager lets you check for compromised passwords, make sure to do so and promptly change any password that may have been exposed in a data breach. Alternatively, you could follow Have I Been Pwned's Latest Breaches feed with the help of a news aggregator.

Creating strong passwords¶

Passwords¶

A lot of services impose certain criteria when it comes to passwords, including a minimum or maximum length, as well as which special characters, if any, can be used. You should use your password manager's built-in password generator to create passwords that are as long and complex as the service will allow by including capitalized and lowercase letters, numbers and special characters.

If you need a password you can memorize, we recommend a diceware passphrase.

Diceware Passphrases¶

Diceware is a method for creating passphrases which are easy to remember, but hard to guess.

Diceware passphrases are a great option when you need to memorize or manually input your credentials, such as for your password manager's master password or your device's encryption password.

An example of a diceware passphrase is viewable fastness reluctant squishy seventeen shown pencil.

To generate a diceware passphrase using real dice, follow these steps:

Note

These instructions assume that you are using EFF's large wordlist to generate the passphrase, which requires five dice rolls per word. Other wordlists may require more or less rolls per word, and may require a different amount of words to achieve the same entropy.

Roll a six-sided die five times, noting down the number after each roll.
As an example, let's say you rolled 2-5-2-6-6. Look through the EFF's large wordlist for the word that corresponds to 25266.
You will find the word encrypt. Write that word down.
Repeat this process until your passphrase has as many words as you need, which you should separate with a space.

Important

You should not re-roll words until you get a combination of words that appeal to you. The process should be completely random.

If you don't have access to or would prefer to not use real dice, you can use your password manager's built-in password generator, as most of them have the option to generate diceware passphrases in addition to regular passwords.

We recommend using EFF's large wordlist to generate your diceware passphrases, as it offers the exact same security as the original list, while containing words that are easier to memorize. There are also other wordlists in different languages, if you do not want your passphrase to be in English.

Explanation of entropy and strength of diceware passphrases

To demonstrate how strong diceware passphrases are, we'll use the aforementioned seven word passphrase (viewable fastness reluctant squishy seventeen shown pencil) and EFF's large wordlist as an example.

One metric to determine the strength of a diceware passphrase is how much entropy it has. The entropy per word in a diceware passphrase is calculated as \(\text{log}_2(\text{WordsInList})\) and the overall entropy of the passphrase is calculated as \(\text{log}_2(\text{WordsInList}^\text{WordsInPhrase})\).

Therefore, each word in the aforementioned list results in ~12.9 bits of entropy (\(\text{log}_2(7776)\)), and a seven word passphrase derived from it has ~90.47 bits of entropy (\(\text{log}_2(7776^7)\)).

The EFF's large wordlist contains 7776 unique words. To calculate the amount of possible passphrases, all we have to do is \(\text{WordsInList}^\text{WordsInPhrase}\), or in our case, \(7776^7\).

Let's put all of this in perspective: A seven word passphrase using EFF's large wordlist is one of ~1,719,070,799,748,422,500,000,000,000 possible passphrases.

On average, it takes trying 50% of all the possible combinations to guess your phrase. With that in mind, even if your adversary is capable of ~1,000,000,000,000 guesses per second, it would still take them ~27,255,689 years to guess your passphrase. That is the case even if the following things are true:

Your adversary knows that you used the diceware method.
Your adversary knows the specific wordlist that you used.
Your adversary knows how many words your passphrase contains.

To sum it up, diceware passphrases are your best option when you need something that is both easy to remember and exceptionally strong.

Storing Passwords¶

Password Managers¶

The best way to store your passwords is by using a password manager. They allow you to store your passwords in a file or in the cloud and protect them with a single master password. That way, you will only have to remember one strong password, which lets you access the rest of them.

There are many good options to choose from, both cloud-based and local. Choose one of our recommended password managers and use it to establish strong passwords across all of your accounts. We recommend securing your password manager with a diceware passphrase comprised of at least seven words.

List of recommended password managers

Don't place your passwords and TOTP tokens inside the same password manager

When using TOTP codes as multi-factor authentication, the best security practice is to keep your TOTP codes in a separate app.

Storing your TOTP tokens in the same place as your passwords, while convenient, reduces the accounts to a single factor in the event that an adversary gains access to your password manager.

Furthermore, we do not recommend storing single-use recovery codes in your password manager. Those should be stored separately such as in an encrypted container on an offline storage device.

Backups¶

You should store an encrypted backup of your passwords on multiple storage devices or a cloud storage provider. This can help you access your passwords if something happens to your primary device or the service you are using.