Add draft documentation for overview, FAQ, and user manual.

docs/README.md

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+This folder houses the current set of Sunder documentation.

docs/overview_and_faq.md

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+### Sunder Overview and FAQ 
+
+**What is Sunder?**
+
+Sunder is a user-friendly computer application that allows news organizations to more securely encrypt large files or datasets for long periods of time. It implements a classic distributed trust model - known as Shamir’s Secret Sharing - for sensitive material that allows news organizations to avoid trusting any one journalist with a large sensitive dataset.
+
+This application works by splitting the "secret" - the complex passphrase protecting the files - into shares such that a subset of them can be recombined to recover the original secret. The individual shares can be distributed to people and places that you trust. You can choose how many shares to create, and how many of them are required to reconstitute the secret. 
+
+In this way, trust and risk can be distributed across many different people or locations, so that the compromise, coercion, or error of any small number of them does not result in the loss or theft of the secret.
+
+**How is this useful to journalists?**
+
+News organizations increasingly have access to sensitive leaked datasets - like the Snowden files or the Panama Papers - and are forced to take care of and secure those files indefinitely.  They inevitably run into a variety of problems:
+
+* There will be staff churn - some of the journalists with access to the sensitive material will leave the organization and new ones will come on.
+
+* You need to be able to absolutely trust the journalists who are given access to begin with. How can you give access to journalists while not trusting that one person with an encryption key?
+
+* You have to worry about someone malicious gaining access to the files by stealing them and attempt to break or circumvent the encryption in some way.
+
+* You have to prepare for the ‘hit by the bus’ factor. What if something happens where you lose the only journalist(s) who have access to a dataset and you are locked out indefinitely?
+
+**How does it work?**
+
+Sunder is an easy-to-use graphical interface that allows you to take text or files and encrypt them while splitting the encryption key into a number of ‘secret shares’ of your choice, which can then be distributed to any number of journalists on your team. You can then designate how many of those shares have to be combined to open the file.
+
+For example, if you have ten journalists you want to distribute trust to, Sunder will generate a passphrase for each of the ten journalists to keep. The news organization can then designate how many journalists will need to use their passphrase to open the file. You can set it to any number you choose - two of the ten journalists can be used to open it, or all ten, or any number in between.
+
+This way you don’t have to trust any one person to keep the passphrase secure - and you can ratchet up the security depending on the number of people you distribute a secret share to.
+
+**Has this existed before?**
+
+The underlying idea behind Sunder is called Shamir’s Secret Sharing, and has been around for decades. Shamir’s Secret Sharing is a cryptographic concept where a secret is divided into parts, giving each participant its own unique part, where some of the parts or all of them are needed in order to reconstruct the secret. 
+
+This type of program has been available in proprietary versions to large corporations and government agencies before, but has been incredibly burdensome to implement for non-technical users. Sunder creates a much easier way for small organizations to use the concept of Shamir’s Secret Sharing without going through an incredibly complicated process.
+
+**How secure is Sunder?**
+
+Shamir’s Secret Sharing scheme is *information-theoretically secure*. What this means is that it’s secure against an adversary with infinite computing power; this is due to the fact that nothing about the secret is leaked if you have fewer than the required number of shares necessary to rebuild it. This notion of security even predates Shamir’s Secret Sharing by several decades, as it was developed over the mid to late 1940s by the father of information theory, Claude Shannon.
+
+However, the software is currently an alpha release. While we hope users to try it out and give us feedback, and we hope developers and security experts will join in on the open-source development of the project, we strongly recommend **AGAINST **anyone using it for potentially life-threatening situations.
+
+**Why would I use this?**
+
+* **Security** - If you have a very important file or document whose theft would be devastating, this tool might be of interest. By splitting a secret into many shares, you make it exponentially harder for an attacker to compromise the secret, because they have to compromise several of the shares to recover the original.
+
+* **Redundancy** - If you have a secret that must not be lost, it is bad practice to keep it in only one place, or in only one person’s head. By splitting a secret you can store the shares in many different places—geographically or with different people--so that the loss of one of the shares does not mean the loss of the secret. Doing this with Sunder is better than simply copying the original secret because the shareholders do not have individual access to the secret, nor can the secret be stolen by compromising any individual backup location.
+
+* **Distributed trust** - Splitting a secret means that no person has access to it when acting alone. Accessing the secret requires the cooperation and consent of some number of other people.
+
+### When is this not appropriate?
+
+* **Frequent access** - If you need to access the secret frequently, daily or even weekly, this is probably not the right scheme for you. Reconstituting the secret requires that a quorum of the shareholders are present. If that is going to be a burden then you consider other options.
+
+### What are other real world examples?
+
+While the application we are releasing is aimed at journalists, secret splitting can be useful in other areas beyond journalism. For example: 
+
+* **Access after death **- Some people use this scheme to share their passwords with close friends and relatives so that their digital lives can be accessed in the event of their passing or becoming incapacitated. If enough of your friends and family agree that you would want them to recover the secret and access your documents, then they have that capability, but otherwise none of them alone can do so.
+
+* **Signing keys** - If your organization publishes signed software, you might want to cryptographically enforce a two-developer rule, i.e. never sign something unless two developers agree that it should be signed. One way to accomplish this would be to use Shamir’s scheme, which has the added benefit of making your key harder to steal.
+
+* **Backup access to personal secrets** - This tool can also be used in cases where the secrets are distributed not to people, but to isolated hard drives. For example you might backup a key by placing one share on a USB key you carry with you, one on a backup hard drive, and one on a personal computer (with a two-of-three splitting scheme). This setup would allow you to recover a lost key as long you still had two of three (USB, hard drive, or computer).
+
+* **Bitcoin** - The keys to the cold-storage vaults of [at least one major bitcoin company are secured](https://medium.com/the-coinbase-blog/how-coinbase-builds-secure-infrastructure-to-store-bitcoin-in-the-cloud-30a6504e40ba#.5qukxh1q5) using this scheme. The shares of the secret are distributed to trusted executives and board members. So if the funds need to be accessed, that can only be done by consensus. This is an example of an extremely sensitive secret (perhaps a $100 million secret), that also must not be lost (because the money would be lost with it). This is also a nice example of distribution of trust, where no single person should be unilaterally trusted with the secret.
+