scat

scat is a password scatterer. It allows the generation of unique passwords for each service, website, email address or account you might have, all from a single password.

Disclaimer

scat is not the best one can achieve in security. If you are interested in a more secure system, look at pwsafe for instance. The system is potentially vulnerable when an attacker can gather generated keys.

That being said, if you tend to reuse the same password everywhere and do not want to store all passwords in a database, you might be better off using scat than to keep using the same password or a slight variation for each website.

Motivation

Nowadays, accounts for many services such as Facebook, Twitter, Reddit, Google, Amazon, your bank account, etc. are needed. In a perfect world, all those accounts would have different passwords, so that, if someone gets to know, let's say, your Facebook password, they don't gain access to your bank account and your money as well. But, on the other hand, who would like to remember dozens and dozens of different passwords?

scat is the solution to this problem. It allows you to safely generate for each website or service you suscribe to a unique password. All you have to do is remember a single, as strong as possible, password.

Given the same service and password, scat will always generate the same password, so you don't have to remember them or note them down! Passwords generated by scat are very secure and independant of each others. If by misfortune one of the generated password is compromised, all other passwords are still safe, and so is the password you used to generate them.

Example

To use scat, simply call it specifying which key, or service, it must generate a password for. Then, simply enter your password (which is, in this example, pony1234):

> scat -c -k "github"
Password:
Confirm:
Generated password:
p3sz\x9vUsn{"Kjzxt

Note that pony1234 is not your github password. It's the original password you use to generate other passwords. Never share it, or use it as a password for anything else than scat.

Let's say that you now want to generate a Facebook password:

> scat -c -k "facebook"
Password:
Confirm:
Generated password:
6yorHvhrpj#8Yce:bl

The password generated for Facebook is completely different from the one it generated for GitHub.

Imagine now that your are on an other computer, with no access to your keychain, and you would like to login to Facebook (just for 5 minutes). To your great despair, there is no way you can remember your obscure password! However, as scat is fully deterministic, you can simply call it once more, to generate once again the exact same password, this time from another computer.

> scat -c -k "facebook"
Password:
Confirm:
Generated password:
6yorHvhrpj#8Yce:bl

Caution

scat is not an excuse to use a weak password such as pony1234. Always use a strong password (that you can remember) with scat.

Security

By default, scat will generate password of length 18, using a mix of lower case letters, upper case letters, digits and various ascii symbols. This leads to a password entropy of about 115 bits. Meaning that an attacker knowing which schema you used and able to test a billion password per second would have to wait approximately 50 million times the age of the universe to guess your password correctly. So it's pretty safe.

Now, let's imagine for a second that an attacker gets to know one of your generated password. This is pretty bad, but not as bad as having a single password. Imagine for a second the disaster if your attacker could directly access all your accounts! Knowing a single generated password won't help your attacker much, it is still practically infeasable for him to get to your original password, so all of your other accounts are safe!

Password schemas

As we have just seen, scat generates by default password of length 18. But, it also provides other schemas!

If you want, for some reason, an easily rememberable passphrase, for let's say Facebook, you can use the schema named diceware, which will output 5 words out of the 7776 words of the Diceware list.

> scat -c -k "facebook" -s diceware
Password:
Confirm:
Generated password:
ieee te real sepoy whiff

Or, if you prefer Pokémons:

> scat -c -k "facebook" -s pokemons
Password:
Confirm:
Generated password:
Zapdos 27, Vulpix 43, Venusaur 21, Staryu 12

Summary of available schemas

Name	Comments	Entropy (in bits)
safe	A mix of 18 ascii symbols. (default)	115
alpha	A mix of 18 alphanumeric symbols.	104
parano	78 ascii characters.	512
pokemons	4 classic Pokémons, each with a level up to 100.	55
diceware	5 words out of the diceware's list.	65
pinXX	XX digits. (useful for PIN codes)	3.3 * XX

How it works

Under the hood, scat will use Scrypt, a password-based key derivation function, to generate a huge integer seed. This integer seed will be consumed by scat to generate deterministically a new password from a schema.

Installing

For now, scat is only distributed as a Haskell source code.

1. If you do not have Haskell and Cabal installed, please visit the Haskell website and download the Haskell platform.

2. Once this is done, download the scat code and place yourself in the root directory of the project (in which you should find a file named snap.cabal).

3. Run the command cabal configure && cabal install to install scat.

4. Enjoy!

Contributing

Feel free to contribute to this project! If you have a brilliant idea to make this project better, just say so! If you lack ideas but would like to participate anyway, you can also find here a list of things to do!

Things to do

1. Create other schemas.

2. Let the user specify a size for some schemas. (By specify another command line option).

3. Compatible port in mainstream programming languages.

4. Some other improvements you might want!

Contributors

Name	Contributions
Romain Edelmann	Initial work on the project.