diff --git a/.drone.yml b/.drone.yml
index 428c8c0..8c714f4 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -24,15 +24,26 @@ steps:
   image: clux/muslrust
   commands:
     - cargo build --release
-    - strip target/x86_64-unknown-linux-musl/release/coffer-server
-    - strip target/x86_64-unknown-linux-musl/release/coffer-client
-    - strip target/x86_64-unknown-linux-musl/release/coffer-companion
+    - mkdir coffer-${DRONE_TAG}-x86_64-musl
+    - mv target/x86_64-unknown-linux-musl/release/coffer-server \
+         target/x86_64-unknown-linux-musl/release/coffer-client \
+         target/x86_64-unknown-linux-musl/release/coffer-companion \
+         coffer-${DRONE_TAG}-x86_64-musl
+    - strip coffer-${DRONE_TAG}-x86_64-musl/coffer-server
+    - strip coffer-${DRONE_TAG}-x86_64-musl/coffer-client
+    - strip coffer-${DRONE_TAG}-x86_64-musl/coffer-companion
 
 - name: package
   image: alpine
   commands:
-    - tar cjf coffer-${DRONE_TAG}-x86_64-musl.tar.bz2 target/x86_64-unknown-linux-musl/release/coffer-server target/x86_64-unknown-linux-musl/release/coffer-client target/x86_64-unknown-linux-musl/release/coffer-companion
-    - tar czf coffer-${DRONE_TAG}-x86_64-musl.tar.gz target/x86_64-unknown-linux-musl/release/coffer-server target/x86_64-unknown-linux-musl/release/coffer-client target/x86_64-unknown-linux-musl/release/coffer-companion
+    - tar cjf coffer-${DRONE_TAG}-x86_64-musl.tar.bz2 \
+              coffer-${DRONE_TAG}-x86_64-musl/coffer-server \
+              coffer-${DRONE_TAG}-x86_64-musl/coffer-client \
+              coffer-${DRONE_TAG}-x86_64-musl/coffer-companion
+    - tar czf coffer-${DRONE_TAG}-x86_64-musl.tar.gz \
+              coffer-${DRONE_TAG}-x86_64-musl/coffer-server \
+              coffer-${DRONE_TAG}-x86_64-musl/coffer-client \
+              coffer-${DRONE_TAG}-x86_64-musl/coffer-companion
 
 - name: publish
   image: plugins/gitea-release
diff --git a/.gitattributes b/.gitattributes
index 2c752ed..70e065a 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,2 +1,4 @@
 *.enc filter=lfs diff=lfs merge=lfs -text
 *.cert filter=lfs diff=lfs merge=lfs -text
+overview.png filter=lfs diff=lfs merge=lfs -text
+overview.svg filter=lfs diff=lfs merge=lfs -text
diff --git a/Cargo.lock b/Cargo.lock
index a0befe1..6caef01 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -88,9 +88,7 @@ dependencies = [
  "exec 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_cbor 0.10.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_yaml 0.8.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "structopt 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
diff --git a/README.md b/README.md
index c331c35..88dbf56 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,77 @@
-# Coffer
+# Coffer 
+[![Build Status](https://drone.friedl.net/api/badges/incubator/coffer/status.svg?ref=refs/heads/develop)](https://drone.friedl.net/incubator/coffer)
+
+Coffer is a collection of tools for the simple but secure management of
+application configuration.
+
+It is meant to be flexible and simple, hence does not assume much about your
+environment. Especially, you don't need a kubernetes cluster for running coffer.
+Coffer runs directly on your server, just as well as in a containerized setup or
+a full kubernetes cluster. The only thing Coffer needs is a TCP connection
+between the `coffer-server` (securely holding your configuration) and the
+`coffer-client` (retrieving configuration and setting up your application).
+
+## Overview
+![](overview.png)
+
+## The Parts of Coffer
+Coffer is split into 3 binaries and a supporting library:
+
+* `coffer-server`: The `coffer-server` securely stores configuration data and
+  hands them out to `coffer-clients` upon request
+* `coffer-client`: A `coffer-client` requests configuration data from a
+  `coffer-server`, configures the application and may also start it up
+* `coffer-companion`: A helper for generating certificates and encrypting
+  configuration data
+* `coffer-common`: A common library for all binaries containing common
+  cryptographic operations, protocol code and interface definitions
+
+## Security
+Coffer does not rely on a secure connection or any specifics of the environment.
+Instead security is provided by a basic public key cryptography scheme. This
+gives you, the user, the flexibility to set up your ecosystem according to your
+own security needs.
+
+### Certificates
+Certificates in coffer are the just a keypair consisting of a public and private
+key as used by public key cryptography. So, basically, a certificate is nothing
+more than a tuple of two primes.
+
+Certificates in coffer can be generated by the `coffer-companion`. Every
+`coffer-server` and `coffer-client` need their own certificate. Security
+in coffer squarely depends on these certificates being kept secret.
+
+### Configuration
+Configuration can be written in [toml](https://github.com/toml-lang/toml)
+format. It is secured by encrypting it with the public key of the
+`coffer-server`. This can be done by invoking the `coffer-companion`.
+
+Encrypted configuration can be conveniently stored in VCS (e.g. via git-lfs)
+with your application. As long as the server certificate stays private.
+
+### Communication
+The communication between a `coffer-server` and a `coffer-client` is not and
+does not need to be secured. A `coffer-server` associates configuration data
+with the public keys of `coffer-clients`. Upon request of configuration data the
+server sends back the configuration encrypted with the clients public key. Only
+a client in posession of the corresponding private key can read the response.
+
+### Trust Anchors
+It is worth mentioning some things about trust anchors. Every cryptography
+scheme, no matter how sophisticated, needs, at some point, something that can be
+trusted. In case of HTTPS this is provided by central certificate authorities.
+In case of the encrypted letters to your best friend this might be a pre-shared
+password transmitted over phone in 1972.
+
+From a coffer perspective keys can be trusted. That is, coffer assumes that
+certificates are distributed and kept secret according to your threat model. An
+attacker in control of a certificate can steal secret configuration!
+
+Coffer does not assume a trust anchor for you. Instead, you are free to choose
+your own trust anchor according. In a simple personal server setup this might
+mean just distributing certificates by hand. In a more complex, corporate
+environment you may want to set up a secure, central authority. 
+
+Trust anchors are a trade-off between convenience, complexity and security.
+Coffer lets _you_ choose where along these axis you put your trust anchor.
+
diff --git a/TODO.org b/TODO.org
deleted file mode 100644
index c659c65..0000000
--- a/TODO.org
+++ /dev/null
@@ -1,27 +0,0 @@
-#+TODO: TODO NEXT DONE
-
-* General
-** TODO Add a license
-** TODO Better communication protocol
-** TODO Add tests
-** TODO Readme
-* Coffer Server
-** TODO Double delete if files not kept
-** TODO Add secrets on-the-fly
-** TODO Store secrets in secure memory
-   - Not persisted
-   - Nulled out
-   - Optional encrypted
-* Coffer Client
-** DONE Set environment variables
-   CLOSED: [2019-11-27 Wed 22:51]
-** TODO Send key requests encrypted/signed
-** TODO Secure Communication
-* Coffer Companion
-** TODO Add Subcommands
-   - [X] Generate certificate 
-   - [ ] Seal secrets with certificate
-   - [ ] Open secrets with certificate
-   - [ ] Generate trampolin sh from dockerfile
-* Docker
-** TODO Create Dockerfile for server
diff --git a/coffer-client/Cargo.toml b/coffer-client/Cargo.toml
index a4989f3..e0c56d1 100644
--- a/coffer-client/Cargo.toml
+++ b/coffer-client/Cargo.toml
@@ -12,8 +12,6 @@ log = "0.4"
 env_logger="0.7"
 structopt = "0.3"
 # Communication
-serde = { version = "1.0", features = ["derive"]}
-serde_yaml = "0.8"
 serde_cbor = "0.10.2"
 # Executing subcommand
 exec = "0.3.1"
diff --git a/coffer-client/src/main.rs b/coffer-client/src/main.rs
index 6d215bd..ff8b937 100644
--- a/coffer-client/src/main.rs
+++ b/coffer-client/src/main.rs
@@ -1,20 +1,28 @@
+//! # Coffer client
+//!
+//! Retrieve a secret shard from a `coffer-server`. Secrets in the shard are set
+//! as environment variables for the spawned subcommand `cmd`.
+
 #[allow(unused_imports)]
 use log::{debug, error, info, trace, warn};
 use env_logger;
 
-use structopt::StructOpt;
-
 use std:: {
-    net::{SocketAddr, TcpStream},
+    net::TcpStream,
     error::Error,
     path::PathBuf,
     io::{Write, Read},
     convert::{TryInto, TryFrom}
 };
 
-use coffer_common::certificate::Certificate;
-use coffer_common::coffer::{CofferShard, CofferValue};
+use coffer_common::{
+    coffer::{CofferShard, CofferValue},
+    certificate::Certificate
+};
 
+use structopt::StructOpt;
+
+/// Client for setting up the environment from coffer server secrets
 #[derive(StructOpt, Debug)]
 struct Args {
     /// Address of the coffer server
@@ -75,6 +83,8 @@ fn main() -> Result<(), Box<dyn Error>> {
     Err("Could not spawn sub-command".into())
 }
 
+/// Replaces the `coffer-client` process image with
+/// the subcommand `cmd` with `args`
 fn reap_coffer(cmd: &str, args: &[String]) {
     let mut cmd = exec::Command::new(cmd);
 
diff --git a/coffer-common/src/certificate.rs b/coffer-common/src/certificate.rs
index 893d653..01df7b5 100644
--- a/coffer-common/src/certificate.rs
+++ b/coffer-common/src/certificate.rs
@@ -1,18 +1,27 @@
-//! Common certificate handling and encryption
-
+//! A keypair container providing functionality for signing, encryption and
+//! decryption
+//!
+//! # Base libraries
+//! The cryptographic operations exposed by this module are based on the
+//! [NaCl](http://nacl.cr.yp.to/) fork [libsodium](https://libsodium.org) as
+//! exposed by the rust bindings [sodiumoxide](https://crates.io/crates/sodiumoxide).
+//!
 #[allow(unused_imports)]
 use log::{debug, error, info, trace, warn};
 
-use std::path::Path;
-use std::io::BufReader;
-use std::fs::File;
-use std::fmt::{Debug, Formatter};
+use std::{
+    path::Path,
+    io::BufReader,
+    fs::File,
+};
+
+#[allow(unused_imports)]
+use std::ops::Deref; // we use this but rustc doesn't know
 
 use quick_error::quick_error;
 
 use seckey::SecKey;
-use sodiumoxide::crypto::box_;
-use sodiumoxide::crypto::sealedbox;
+use sodiumoxide::crypto::{box_, sealedbox};
 use serde::{Serialize, Deserialize};
 use serde_cbor;
 
@@ -25,22 +34,51 @@ quick_error! {
         Io(err: std::io::Error) {
             from()
         }
-        SecKey
+        SecKey {
+            from(CertificateInner)
+        }
         Crypto
     }
 }
 
-/// A secure container for certificates
+/// A secure container for a keypair
 ///
-/// # Certificate
+/// Secure means a best effort approach to:
+/// - Prevent swapping memory to disk
+/// - Zeroing out memory upon dropping
+/// - Prevent other processes and buffer overflows to access the secure memory
+///   area
 ///
-/// A certificate consists of a public and a private key in a secure memory
-/// area. With a certificate data sealed and opened.
+/// These guarantees are currently *not* reliable. If you threat model contains
+/// targeted attacks against coffer memory, additional precautions have to be
+/// taken.
 pub struct Certificate {
     inner: SecKey<CertificateInner>
 }
 
+// The SecKeyReadGuard prevents convenience methods for handing out references
+// to private/public keys (reference outlives SecKeyReadGuard). Hence below
+// macros are shortcut projections that can be used after a read guard is
+// created
+
+// Get the public key
+macro_rules! pk {
+  ($cert:ident) => {
+    &$cert.inner.read().public_key
+  };
+}
+
+// Get the private key
+macro_rules! sk {
+  ($cert:ident) => {
+    &$cert.inner.read().private_key
+  };
+}
+
+// Certificate and its inner SecKey own their
+// raw pointer without any thread local behaviour
 unsafe impl Send for Certificate {}
+// After initialization, certificate is read-only
 unsafe impl Sync for Certificate {}
 
 #[derive(Serialize, Deserialize)]
@@ -49,13 +87,8 @@ struct CertificateInner {
     private_key: box_::SecretKey
 }
 
-impl Debug for CertificateInner {
-    fn fmt(&self, fmt: &mut Formatter<'_>) -> std::fmt::Result {
-        write!(fmt, "<Certificate Hidden>")
-    }
-}
-
 impl Certificate {
+  /// Initialize with a generated keypair
     pub fn new() -> Result<Certificate, CertificateError> {
         debug!{"Generating new certificate"}
         let (public_key, private_key) = box_::gen_keypair();
@@ -66,6 +99,7 @@ impl Certificate {
         Ok(Certificate{inner})
     }
 
+    /// Initialize from a serialized certificate in [cbor](https://cbor.io/) format
     pub fn new_from_cbor<T: AsRef<Path>>(path: T) -> Result<Certificate, CertificateError> {
         debug!{"Reading certificate from {}", path.as_ref().display()}
         let f = File::open(path)?;
@@ -76,40 +110,35 @@ impl Certificate {
         Ok(Certificate{inner})
     }
 
+    /// Serialize a certificate to a file in [cbor](https://cbor.io/) format
     #[cfg(feature = "export")]
     pub fn to_cbor(&self) -> Result<Vec<u8>, CertificateError> {
-        let inner_cert = &*self.inner.read();
-        let cbor = serde_cbor::to_vec(inner_cert)?;
+        let read_guard = self.inner.read();
+
+        let cbor = serde_cbor::to_vec(read_guard.deref())?;
+
         Ok(cbor)
     }
 
+    /// Clone the bytes of the public key
     pub fn public_key(&self) -> Vec<u8> {
-        self.inner.read().public_key.as_ref().to_owned()
+        pk!(self).as_ref().to_owned()
     }
 
+    /// Clone the bytes of the private key
     #[cfg(feature = "export")]
     pub fn secret_key(&self) -> Vec<u8> {
-        self.inner.read().private_key.as_ref().to_owned()
+        sk!(self).as_ref().to_owned()
     }
 
+    /// Open a [sealed box](https://download.libsodium.org/doc/public-key_cryptography/sealed_boxes)
     pub fn open(&self, c: &[u8]) -> Result<Vec<u8>, CertificateError> {
-        let pk = &self.inner.read().public_key;
-        let sk = &self.inner.read().private_key;
-
-        sealedbox::open(c, pk, sk)
+        sealedbox::open(c, pk!{self}, sk!{self})
             .map_err(|_| CertificateError::Crypto)
     }
 
+    /// Seal a message in a [sealed box](https://download.libsodium.org/doc/public-key_cryptography/sealed_boxes)
     pub fn seal(&self, message: &[u8]) -> Result<Vec<u8>, CertificateError> {
-        let pk = &self.inner.read().public_key;
-
-        Ok(sealedbox::seal(message, pk))
-    }
-}
-
-impl <T: AsRef<Path>> From<T> for Certificate {
-    fn from(path: T) -> Self {
-        Certificate::new_from_cbor(&path)
-            .expect(&format!{"Could not read certificate from {}", path.as_ref().display()})
+        Ok(sealedbox::seal(message, pk!{self}))
     }
 }
diff --git a/coffer-common/src/coffer.rs b/coffer-common/src/coffer.rs
index b43ac17..3f86581 100644
--- a/coffer-common/src/coffer.rs
+++ b/coffer-common/src/coffer.rs
@@ -1,17 +1,85 @@
 //! A storage container for client data
+//!
+//! Coffer supports separated client data by `CofferShard`s. Content of a shard
+//! is a key-value store with typed values.
+//!
+//! # Coffer files
+//! A `Coffer` can be read from a [toml](https://github.com/toml-lang/)
+//! file in a specific format.
+//!
+//! ## Shards
+//! A `CofferShard` is identified by a toml table with a field `id` containing
+//! the unique shard id.
+//!
+//! Tables can be nested for grouping shards together. The grouping is not
+//! necessarily reflected in the deserialized `Coffer`, as shards can be
+//! uniquely identified by their id.
+//!
+//! Shards (tables with an id) cannot be nested.
+//!
+//! A simple shard with no data
+//! ```toml
+//!   [app]
+//!   id = "1"
+//! ```
+//!
+//! Grouped shard
+//! ```toml
+//!   [app]
+//!   [app.frontend]
+//!   id = "1"
+//!
+//!   [app.backend]
+//!   id = "2"
+//! ```
+//!
+//! Nested shards (invalid)
+//! ```toml
+//!   [app]
+//!   id = "1" # app is a shard since it has an id
+//!   [app.frontend] # invalid, can't nest shards inside other shards
+//!   id = "2"
+//! ```
+//!
+//! ## Values
+//! Shards can contain a subset of toml values. The currently supported toml
+//! values are:
+//! - [String](https://github.com/toml-lang/toml#user-content-string)
+//! - [Integer](https://github.com/toml-lang/toml#user-content-integer)
+//! - [Float](https://github.com/toml-lang/toml#user-content-float)
+//! - [Boolean](https://github.com/toml-lang/toml#user-content-boolean)
+//!
+//! ## Example
+//! ```toml
+//!   [app]
+//!   [app.frontend]
+//!   id = "1"
+//!   password = "admin"
+//!   font_size = 1.4
+//!
+//!   [app.backend]
+//!   id = "2"
+//!   cors = true
+//!
+//!   [database]
+//!   id = "0"
+//!   user = "root"
+//!   passwort = "toor"
+//! ```
+//!
 #[allow(unused_imports)]
 use log::{debug, error, info, trace, warn};
 
-use std::fmt::Debug;
-use std::path::Path;
-use std::fs::File;
-use std::io::{BufReader, Read};
-
-use toml::Value as TomlValue;
-
-use serde::{Serialize, Deserialize};
+use std::{
+  fmt::Debug,
+  fs::File,
+  io::{BufReader, Read},
+  path::Path,
+};
 
 use quick_error::quick_error;
+use toml::Value as TomlValue;
+use serde::{Serialize, Deserialize};
 
 quick_error! {
     #[derive(Debug)]
@@ -28,7 +96,7 @@ quick_error! {
 
 pub type CofferResult<T> = Result<T, CofferError>;
 
-/// Values supported by a `Coffer`
+/// Values supported by `Coffer`
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub enum CofferValue {
     /// A UTF-8 encoded string
@@ -37,35 +105,38 @@ pub enum CofferValue {
     Integer(i32),
     /// A 32-bit float
     Float(f32),
-    // A boolean
+    /// A boolean value
     Boolean(bool)
 }
 
+/// A `CofferKey` defining the shard and the key into the kv-store
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq, Hash)]
 pub struct CofferKey {
     pub shard: String,
     pub key: String
 }
 
-#[derive(Debug, Serialize, Deserialize)]
+/// A key-value store for client data
+#[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct CofferShard(pub Vec<(String, CofferValue)>);
 
-/// Interface for interacting with a `Coffer`
+/// Trait for `Coffer`
 pub trait Coffer {
-    /// Put `value` at `path`. Errors if there is already a value at `path`.
+    /// Put `value` at `key`. Errors if there is already a value for `key`.
     fn put(&mut self, key: CofferKey, value: CofferValue) -> CofferResult<()>;
 
-    /// Push `value` to `path`. Replaces existing values.
+    /// Push `value` to `key`. Replaces existing values.
     fn push(&mut self, key: CofferKey, value: CofferValue);
 
-    /// Retrieve `value` at path. Errors if there is no `value` at path.
-    fn get(&self, key: &CofferKey) -> CofferResult<CofferValue>;
+    /// Retrieve `value` at path. `None` if there is no `value` for `key`.
+    fn get(&self, key: &CofferKey) -> Option<CofferValue>;
 
-    /// Retrieve `value` at path. Errors if there is no `value` at path.
-    fn get_shard<T>(&self, shard: T) -> CofferResult<CofferShard>
+    /// Retrieve an entire shard. `None` if there is no `CofferShard` for `shard`.
+    fn get_shard<T>(&self, shard: T) -> Option<CofferShard>
     where T: AsRef<str>;
 
-    fn from_toml_file(toml_path: &Path) -> Self
+    /// Deserializes a `Coffer` from a toml file
+    fn from_toml_path(toml_path: &Path) -> Self
     where Self: Coffer + Default
     {
         // read the secrets file into a temporary string
@@ -135,4 +206,5 @@ pub trait Coffer {
             self.put(CofferKey{shard, key}, value).unwrap();
         }
     }
+
 }
diff --git a/coffer-common/src/keyring.rs b/coffer-common/src/keyring.rs
index 7179b15..4a29986 100644
--- a/coffer-common/src/keyring.rs
+++ b/coffer-common/src/keyring.rs
@@ -1,3 +1,4 @@
+//! Certificate of the keyring owner plus known and trusted public keys
 #[allow(unused_imports)]
 use log::{debug, error, info, trace, warn};
 
@@ -36,28 +37,36 @@ quick_error! {
     }
 }
 
+/// Keyring container
+///
+/// A keyring constists of the owner's certificate and
+/// the known and trusted public keys of the keyring owner
 pub struct Keyring {
     certificate: Certificate,
     known_keys: HashMap<Vec<u8>, box_::PublicKey>
 }
 
 impl Keyring {
+  /// Create a new keyring
     pub fn new(certificate: Certificate) -> Keyring {
         Keyring {
-            certificate: certificate,
+            certificate,
             known_keys: HashMap::new()
         }
     }
 
+    /// Deserialize a keyring from a file in [cbor](https://cbor.io) format
     pub fn new_from_path<T>(certificate_path: T) -> Keyring
     where T: AsRef<Path>
     {
         Keyring {
-            certificate: Certificate::from(certificate_path),
+            certificate: Certificate::new_from_cbor(certificate_path).unwrap(),
             known_keys: HashMap::new()
         }
     }
 
+    /// Add the table ids of a `Coffer` in toml format as known keys to the keyring
+    // TODO: This needs to be refactored. Keyring shouldn't be that tightly bound to coffer format
     pub fn add_known_keys_toml(&mut self, toml: &str) -> Result<(), KeyringError> {
         // parse the string into a toml Table
         let clients: toml::value::Table = match toml.parse::<TomlValue>().unwrap() {
@@ -100,11 +109,21 @@ impl Keyring {
         Ok(())
     }
 
+    /// Open a sealed message with the keyring owner's certificate
     pub fn open(&self, message: &[u8]) -> Result<Vec<u8>, KeyringError> {
         self.certificate.open(message)
             .map_err(KeyringError::from)
     }
 
+    /// Seal a message for a client in the keyring
+    // TODO: Does this make sense?
+    //   - What is a client in context of a keyring?
+    //   - Why do we need to store trusted public keys in a keyring and not just
+    //     encrypt for a pub key. Sealing does not need certificate.
+    //   => We need authenticated encryption here. Sealed boxes can be tampered with by a MITM
+    //      https://download.libsodium.org/doc/public-key_cryptography/authenticated_encryption
+    //      I.e. a client could retrieve forged secrets by a attacker-controlled server, even if the
+    //      real server's certificate was not exposed.
     pub fn seal(&self, client: &[u8], message: &[u8]) -> Result<Vec<u8>, KeyringError> {
         let client_key = self.known_keys.get(client)
             .ok_or(KeyringError::UnkownClientKey)?;
diff --git a/coffer-common/src/lib.rs b/coffer-common/src/lib.rs
index 36b33b7..7984de1 100644
--- a/coffer-common/src/lib.rs
+++ b/coffer-common/src/lib.rs
@@ -1,16 +1,5 @@
-//! Common base for coffer binaries
-
-#[allow(unused_imports)]
-use log::{debug, error, info, trace, warn};
+//! Common traits and function for coffer implementations
 
 pub mod certificate;
 pub mod coffer;
 pub mod keyring;
-
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
-    }
-}
diff --git a/coffer-companion/src/certificate.rs b/coffer-companion/src/certificate.rs
index 32f4826..f9a28ce 100644
--- a/coffer-companion/src/certificate.rs
+++ b/coffer-companion/src/certificate.rs
@@ -10,7 +10,7 @@ pub fn generate_key(out: PathBuf) {
     let cert = certificate.to_cbor().unwrap();
 
     let mut writer = File::create(&out)
-        .expect(&format!{"Could not create out file {}", &out.display()});
+        .unwrap_or_else(|_| panic!{"Could not create out file {}", &out.display()});
 
     writer.write_all(&cert).unwrap();
 }
diff --git a/coffer-server/src/coffer_map.rs b/coffer-server/src/coffer_map.rs
index 46acd8a..6d2d261 100644
--- a/coffer-server/src/coffer_map.rs
+++ b/coffer-server/src/coffer_map.rs
@@ -7,7 +7,7 @@ use std::sync::RwLock;
 use std::sync::RwLockReadGuard;
 use std::sync::RwLockWriteGuard;
 
-use std::collections::HashMap;
+use std::collections::hash_map::{HashMap, Entry};
 
 use coffer_common::coffer::*;
 
@@ -29,13 +29,15 @@ impl CofferMap {
 }
 
 impl Coffer for CofferMap {
-    fn put(&mut self, key: CofferKey, value: CofferValue) -> CofferResult<()> {
+  fn put(&mut self, key: CofferKey, value: CofferValue) -> CofferResult<()> {
         let mut lock = self.write();
 
         match lock.get_mut(&key.shard) {
             Some(shard) => {
-                if shard.contains_key(&key.key) { Err(CofferError::Msg("Key exists")) }
-                else { shard.insert(key.key, value); Ok(()) }
+                match shard.entry(key.key) {
+                    Entry::Occupied(_) => Err(CofferError::Msg("Key exists")),
+                    Entry::Vacant(v) => { v.insert(value); Ok(()) }
+                }
             }
             None => {
                 lock.insert(key.shard.clone(), HashMap::new());
@@ -59,33 +61,29 @@ impl Coffer for CofferMap {
         }
     }
 
-    fn get(&self, key: &CofferKey) -> CofferResult<CofferValue> {
+    fn get(&self, key: &CofferKey) -> Option<CofferValue> {
         let lock = self.read();
 
-        let res = lock.get(&key.shard)
+        lock.get(&key.shard)
             .and_then( |shard| { shard.get(&key.key) } )
-            .ok_or(CofferError::Msg("Key not found"))?;
-
-        Ok(res.clone())
+            .map(|o| o.clone())
     }
 
-    fn get_shard<T>(&self, shard: T) -> CofferResult<CofferShard>
+    fn get_shard<T>(&self, shard: T) -> Option<CofferShard>
     where T: AsRef<str>
     {
         let lock = self.read();
 
         debug!{"Coffer {:?}", *lock}
 
-        let coffer_shard = lock.get(shard.as_ref())
-            .ok_or(CofferError::Msg("Shard not found"))?;
+        let map_to_vec = |map: &HashMap<String, CofferValue>| {
+            map.iter()
+               .map(|(k,v)| (k.clone(), v.clone()))
+               .collect::<Vec<(String, CofferValue)>>()
+        };
 
-        let mut res = CofferShard(Vec::new());
-
-        for (k,v) in coffer_shard {
-            res.0.push((k.clone(), v.clone()));
-        }
-
-        Ok(res)
+        lock.get(shard.as_ref())
+            .and_then(|s| Some(CofferShard(map_to_vec(s))))
     }
 }
 
diff --git a/coffer-server/src/server.rs b/coffer-server/src/server.rs
index 3139bcb..74dd5ef 100644
--- a/coffer-server/src/server.rs
+++ b/coffer-server/src/server.rs
@@ -59,7 +59,7 @@ where C: Coffer + Send + Sync + 'static
 
         debug!{"Binding to socket {:?}", socket}
         let mut listener = TcpListener::bind(socket).await
-            .expect(format!{"Could not bind to socket {}", socket}.as_str());
+            .expect("Could not bind to socket");
 
         let server = async move {
             let mut incoming = listener.incoming();
diff --git a/overview.png b/overview.png
new file mode 100644
index 0000000..7df19d7
--- /dev/null
+++ b/overview.png
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:4f94bbbadfc6999de61a0a7c96f3d6ed6ac8ba2f00cbeb719faf8d8d3c83a4dd
+size 52769
diff --git a/overview.svg b/overview.svg
new file mode 100644
index 0000000..9413c1e
--- /dev/null
+++ b/overview.svg
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:20e3bc8d9a769d67cbfab6f75cd3c403630a527a42c33767e1b4e1597b336167
+size 46743