Strongman Strongman

Free Open Source Online Password Manager


Strongman is a free open-source online password manager written in javascript with a touch of php.

Strongman has two basic modes of functionality:

  1. Compute Mode: This mode uses the master password combined with the username and domain to create "computed" passwords (similar to lesspass). In this mode, only a "password profile" is stored on the server, not the password itself. This mode is used when the 'Compute' button is used.
  2. Encrypt Mode: This mode is used when you click the 'Save' button. It allows saving any user-specified password, encrypted (AES-256) using the master password and then sent to the server for storage. This same encryption is also used for "secure notes."

The emphasis is on speed, security, and simplicity. Open Strongman Password Manager


Why I Created Strongman

There are many password managers. Why did I invent a new one?

In the first place, I became convinced that for proper security for online accounts, everyone should use a password manager. But I couldn't fully trust a program that wasn't open source, which ruled out all the commercial ones I knew about. Also, I wanted to be able to host it on my own server. That greatly reduced my options. I also wanted great speed and ease of use.

I found lesspass, which is open source and can be self-hosted. It nearly filled my needs, except migrating to it would mean I would have to change all my site passwords. Furthermore, there's no way to change the master password without changing all the website passwords it generates.

So I set out to build my ideal password manager. Essentially I adopted the extremely secure computed passwords of lesspass, but added the ability to use AES-256 encryption for "custom" passwords and "secure notes." This way, one can optionally store any password one wants. This also allowed me to add the ability to change the master password.


When changing a master password in Strongman, all the computed passwords associated with the old master password are converted to AES-256 encrypted passwords using the new master password.


Installation is not necessary for most users, since the Strongman project hosts the web app for free public access:

If you wish to run the web app on your own server, or to help with development, download the project from the github repository. Upload the "app" directory to any location accessible to your php7.1+-enabled web server. Make sure the "data-source" directory is writable by your web server user. You should also be sure that the site can't be accessed by both the base domain and the www subdomain, so that cookies can work properly. That's it. There's no database. Account information is stored in files, one file per master password.

Strongman Security

Security Overview

According to a security analysis presented at the 23rd Usenix Security Symposium in 2014, 80% of the web-based password managers tested were insecure. Strongman should be immune to the cited vulnerabilities due to its statelessness as well as the lack of vulnerable features such as bookmarklets, one-time passwords, and shared passwords. I invite others to perform a security audit for Strongman.

Computed Passwords

Strongman allows lesspass-style computed passwords, which does not involve storing the password at all. The password is "recalculated" from the master password, domain name, username, and password options, such as length and character sets. For these computed passwords, only a "profile" is stored. Here is an example "profile" entry from my own Strongman account. (I have modified the email address.)

[] = 7,14,1,,0,1542057929

In this case, is the domain name, and is the username. The other profile information is:

7: bitfield-encoded character set. "7" means use upper/lowercase letters and numbers, but no special characters.  
14: password length  
1: password sequence number (This is incremented to create a new computed password.)  
empty: encrypted secure notes (none in this case)
0: Password category number
1542057929: timestamp to keep track of password age

In sum, computed passwords involve no password storage whatsoever. However, they are very inflexible. Computed passwords cannot be modified by the user other than specifying the character set and length. So if you already have some secure passwords that you'd like to keep using with Strongman, computed passwords are not a solution. Plus, as explained in Why I Created Strongman, the master password cannot be changed without changing all the computed passwords.

To solve this problem, Strongman allows storing AES-encrypted passwords and notes, described in the next section.

AES-Encrypted Passwords and Notes

Whenever you need to store a particular password (rather than use a computed one) you click the "Save" button in Strongman. That causes the password to be encrypted (by the webpage, using javascript) and then sent to the server for storage. This is military-grade encryption, and in my opinion is every bit as secure as the computed passwords. When using encrypted passwords, Strongman remains stateless. Futhermore, the AES-encryption takes place in the browser, before being transmitted to the server for storage.

In addition to encrypted passwords, Strongman offers encrypted secure notes. This allows you to add any sort of information to either a computed or an encrypted password entry.

Here's an example of an encrypted password entry from my own Strongman account:

invoice@ = 15,14,1,fc430283546cf012faf69539a13c5bd4,0,cb4c00b93772d665d6e8f8158f09779f,1539199590

Here, is the domain name, and invoice@ is the username. The other profile information is:

15: character sets (ignored)  
14: password length (ignored)  
1: password sequence number (ignored)  
fc430283546cf012faf69539a13c5bd4: AES-256 encrypted note  
0: Password category number
cb4c00b93772d665d6e8f8158f09779f: AES-256 encrypted password  
1539199590: timestamp to keep track of password age

The Clipboard

The clipboard has been called an insecure way to transport passwords, since others users on your computer as well as all the software on your computer has access to the clipboard.

However, I think it's generally true that if you have to worry about security on your computer, you probably can't safely use passwords in a browser, period. The browser, for example, is going to get your password. Computer memory may contain your password. If the computer is compromised, so is the password. (Tip: if you want to avoid almost all risk from viruses and malware, use Linux.)

Let's assume that your computer is not compromised. Still, it is probably not a good idea to leave passwords copied to the clipboard when you are not using it.

To make it easy to clear the clipboard, any clipboard manager you may be using should be disabled before using Strongman. This is because a clipboard manager stores past clipboard entries. If no clipboard manager is active, the clipboard will have only one entry: the current entry. Then, when you are done copy-pasting passwords, all you have to do is clear the clipboard, and passwords are not left behind. Strongman now provides a convenient "clear clipboard" icon (above the site password field) to do this. (Tip: hover the mouse over icons to show their functions.)

Of course, in addition to clearing the clipboard when you leave your computer, you will probably want to clear the master password and any site password from the Strongman app. This is easily done by clicking the lock icon above the master password field. (Note that this password clearing is automatically done whenever you either close or navigate away from the Strongman app page.)

Password clearing can also be done automatically after a set period of inactivity. In the Strongman app, look under Settings and Tools/General Settings.

The Master Password

The Password Dilema

It is surprisingly difficult for a human to choose a strong password. Humans are not made to think at random; we are creatures of patterns and habits. On the other hand, random (machine chosen) passwords consisting of letters, numbers, and symbols are hard to memorize. How would you like to memorize this example 14-character password: wyY#XiQ1h0E/2~?

On the other hand, simply mangling dictionary words to create a password might look secure, but it probably isn't. Here's a web comic with commentary that illustrates that point well. The conclusion drawn by the comic is "Through 20 years of effort, we've successfully trained everyone to use passwords that are hard for humans to remember, but easy for computers to guess."

Diceware Passwords

This is where "Diceware" passwords come to the rescue. It turns out that humans ARE capable of easily memorizing "passphrases" consisting of, say, 7 random words, taken from a "Diceware" dictionary of 7,776 words. This results in a passphrase which is similar in entropy (difficulty to guess) to the 14 character password. Here is an example 7-word Diceware passphrase: "catalyst sedative certify unused gap dodge alienate".

If you're not completely convinced that a random series of words (Diceware passphrase) is far better than a random or contrived series of characters, please read this excellent article about Diceware. When you are ready to obtain a Diceware passphrase, take a look at this excellent online Diceware passphrase generator. In addition to generating passphrases using the browser's built-in random number generator, you can use real dice with it.

As a final note: if a brute force attacker were to obtain a password hash created from a 7-word Diceware passphrase, and if he could muster 1,000,000,000,000 guesses per second (only possible by a nation state player such as the NSA), the average time to guess a 7-word passphrase would be over 27 million years!


Q: Why are some of my settings lost when I close and then reopen the browser?
A: The following Strongman settings are all stored in browser cookies:

  1. Online status
  2. Domain Incremental Search
  3. Autoclear seconds
  4. Permit non-Diceware Master Password
  5. Hide Passwords on Focus

These cookies should not expire for 1000 days, but if you have your browser set to erase cookies upon closing the browser, these (and all other persistent cookies) will be erased, and all the the above settings will be reset to the defaults.

Q: Isn't it terribly insecure to copy a password to the clipboard? Clipboard data is available to any user or program on the computer!
A: It's true that the clipboard is potentially a security vulnerability. On the other hand, it is the only practical way to transfer complex passwords to browser input fields. Read more under Security.