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+# scat
+
+`scat` is a password *scat*terer. It allows the generation of unique passwords for each service, such as
+website, email address or desktop account, from a single password.
+
+## 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. But, on the other hand, who would like to remember dozens and dozens of passwords?
+
+`scat` is the solution to this problem. It allows you to safely generate for each website a unique password from a single known password.
+If by misfortune one of the generated password is compromised, all other passwords are still safe.
+
+## Example
+
+To use `scat`, simply call it specifying for which key, or service, it must generate a password.
+Then, simply enter your password (which is, in this example, `pony1234`):
+
+```
+> scat -c -k "github"
+Password:
+Confirm:
+Generated password:
+p3sz\x9vUsn{"Kjzxt
+```
+
+Or, for a Facebook password:
+
+```
+> scat -c -k "facebook"
+Password:
+Confirm:
+Generated password:
+6yorHvhrpj#8Yce:bl
+```
+
+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.
+
+```
+> 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 a list of 7776 words, as provided by [The Diceware Passphrase Home Page][diceware].
+
+```
+> 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][diceware]. | 65
+
+## How it works
+
+Under the hood, `scat` will use `SHA-512`, a cryptographic hash 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][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!
+
+[diceware]: http://world.std.com/~reinhold/diceware.html
+[haskell-platform]: http://www.haskell.org/platform/
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