gravityblast · gravityblast · Dec 5, 2019
diff --git a/_posts/2019-11-27-keycard-explained.md b/_posts/2019-11-27-keycard-explained.md
@@ -0,0 +1,111 @@
+---
+layout: post
+title: The Keycard hardware wallet smartcard explained
+cover: /assets/images/covers/keycard-explained.jpg
+tags:
+- keycard
+- hardware wallet
+- ethereum
+- smartcard
+---
+
+> [Keycard](https://keycard.tech/) is a smartcard that comes with two pre-installed applications, the one the you use as an **hardware wallet paired with
+your devices and authenticated with a PIN**, and the **Cash applet**, which can be used **straight away without any other device**.
+
+Keycard is a smartcard, not to be confused with other nfc tags or cards used only for storage or authentication.
+It works like other hardware wallets, meaning that it's able to generate a private key that never leaves the card and can compute an
+ECDSA signature internally.
+
+Smartcards are known for their very high level hardware security, leveraging all the work done in the banking/telecom/access control world for years,
+allowing us to store wallet keys safely in that they never leave the card.
+The [Keycard software](https://github.com/status-im/status-keycard) is an open-source Javacard applet.
+All sensitive data exchanged between the card and the client, like authentication credentials, is sent over an encrypted secure channel.
+The applet allows deriving keys and signing transactions for any cryptocurrency using the Secp256k1 curve and a 256-bit hash.
+
+
+The two application pre-installed are the Keycard applet and the Cash applets.
+
+The **Keycard applet** implements a full hierarchical deterministic wallet that can be used after pairing the card with a device using a
+pairing password that generates a pairing token subsequently used to open a [secure channel for each session to prevent MITM](https://status.im/keycard_api/sdk/securechannel.html);
+after initialization the card contains a master key that remains on the card;
+an API allows the user to use any valid derivation path to derive a key
+that can be used to sign 32 bytes of data after authenticating with a PIN.
+
+The **Cash applet** is a simplified version of the Keycard applet; at installation time a normal (not extended) key is generated and it remains on the card;
+it doesn't need to be paired or initialized with another device and can be used straight away to sign data.
+
+---
+
+## About Keycard
+
+Some months ago we started distributing Keycards to developers, and in October we had a workshop at Devcon 5.
+
+<blockquote class="twitter-tweet"><p lang="en" dir="ltr">preparing some smartcards for tomorrow&#39;s <a href="https://twitter.com/Keycard_?ref_src=twsrc%5Etfw">@Keycard_</a> workshop here at <a href="https://twitter.com/hashtag/devcon?src=hash&amp;ref_src=twsrc%5Etfw">#devcon</a> 🇯🇵 <a href="https://t.co/oG6N2TrM6B">pic.twitter.com/oG6N2TrM6B</a></p>&mdash; Andrea Franz (@gravityblast) <a href="https://twitter.com/gravityblast/status/1181470270147588096?ref_src=twsrc%5Etfw">October 8, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
+
+---
+
+Some teams and developers already integrated Keycard in their projects,
+like [Status](https://status.im/) (available after V1 is released), [Geth](https://twitter.com/peter_szilagyi/status/1135927489484791808?),
+[Walleth](https://walleth.org/), [Gnosis Safe](https://twitter.com/StefanDGeorge/status/1189885553120104450),
+[Grid+](https://github.com/GridPlus/safe-card), and others.
+
+<blockquote class="twitter-tweet"><p lang="en" dir="ltr">One step closer to the Geth v1.9.0 release! Just merged native support for all these beauties on <a href="https://twitter.com/hashtag/Linux?src=hash&amp;ref_src=twsrc%5Etfw">#Linux</a>, <a href="https://twitter.com/hashtag/macOS?src=hash&amp;ref_src=twsrc%5Etfw">#macOS</a>, <a href="https://twitter.com/hashtag/Windows?src=hash&amp;ref_src=twsrc%5Etfw">#Windows</a> and <a href="https://twitter.com/hashtag/FreeBSD?src=hash&amp;ref_src=twsrc%5Etfw">#FreeBSD</a>! Shoutout to <a href="https://twitter.com/gballet?ref_src=twsrc%5Etfw">@gballet</a>, <a href="https://twitter.com/nicksdjohnson?ref_src=twsrc%5Etfw">@nicksdjohnson</a> and <a href="https://twitter.com/mr_ligi?ref_src=twsrc%5Etfw">@mr_ligi</a> for the team effort of sorting all this out! 😎<a href="https://twitter.com/hashtag/golang?src=hash&amp;ref_src=twsrc%5Etfw">#golang</a> <a href="https://twitter.com/hashtag/Ethereum?src=hash&amp;ref_src=twsrc%5Etfw">#Ethereum</a> <a href="https://twitter.com/Ledger?ref_src=twsrc%5Etfw">@Ledger</a> <a href="https://twitter.com/Trezor?ref_src=twsrc%5Etfw">@Trezor</a> <a href="https://twitter.com/Keycard_?ref_src=twsrc%5Etfw">@Keycard_</a> <a href="https://t.co/1jSj3QmHO1">pic.twitter.com/1jSj3QmHO1</a></p>&mdash; Péter Szilágyi (@peter_szilagyi) <a href="https://twitter.com/peter_szilagyi/status/1135927489484791808?ref_src=twsrc%5Etfw">June 4, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
+
+---
+
+The [Keycard software](https://github.com/status-im/status-keycard) is **completely opensource** and can be installed
+on any smartcard/javacard that meets [these requirements](https://status.im/keycard_api/applet_installation.html#Card-requirements).
+
+<blockquote class="twitter-tweet"><p lang="en" dir="ltr">Magic with <a href="https://twitter.com/Keycard_?ref_src=twsrc%5Etfw">@Keycard_</a> and <a href="https://twitter.com/gnosisSafe?ref_src=twsrc%5Etfw">@gnosisSafe</a>: A true 2FA transaction is signed with a private key on the phone and in addition with a private key in a secure enclave on the Status keycard. The most easy-to-use multisig! It also works with dApps using <a href="https://twitter.com/WalletConnect?ref_src=twsrc%5Etfw">@WalletConnect</a>! <a href="https://t.co/zs8TjyClW1">https://t.co/zs8TjyClW1</a></p>&mdash; Stefan George (@StefanDGeorge) <a href="https://twitter.com/StefanDGeorge/status/1189885553120104450?ref_src=twsrc%5Etfw">October 31, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
+
+---
+
+Keycard is dual interface, NFC and contacts. You can interact with it selecting one of the two applets
+and sending [APDU commands](https://en.wikipedia.org/wiki/Smart_card_application_protocol_data_unit).
+If you don't want to send raw APDU command, you can use our [Java/Android](https://github.com/status-im/status-keycard-java),
+[Swift/iOS](https://github.com/status-im/Keycard.swift), and [Go](https://github.com/status-im/keycard-go) SDKs.
+
+If you want to know more about the available commands, you can check the [Keycard API documentation](https://status.im/keycard_api/).
+
+When you buy a Keycard from [our website](https://get.keycard.tech/), you receive it with the Keycard and Cash applets pre-installed,
+but you can use the [keycard CLI](https://github.com/status-im/keycard-cli) to re-install them or to install them on a different smartcard.
+You can also use the CLI to send custom Keycard or standard Globalplatform commands,
+like explained in an [introductory post](https://discuss.status.im/t/introducing-the-keycard-shell/1178).
+
+The main purpose of the Keycard is to be used as an hardware wallet with the Keycard applet, but we recently added a secondary Cash applet
+that allows the owner to use it straight away without requiring a phone, for example to be used with a merchant point of sale or in
+any other creative way...
+
+<blockquote class="twitter-tweet"><p lang="en" dir="ltr">Simple test app for a point of sale machine 💰 signing a meta transaction with the 💳 <a href="https://twitter.com/Keycard_?ref_src=twsrc%5Etfw">@Keycard_</a> cash applet 💵. The cash applet is a secondary app, the main one is still the hardware wallet app 🔐 that needs pairing password, pin, etc <a href="https://twitter.com/hashtag/ethereum?src=hash&amp;ref_src=twsrc%5Etfw">#ethereum</a> <a href="https://twitter.com/hashtag/smartcard?src=hash&amp;ref_src=twsrc%5Etfw">#smartcard</a> <a href="https://twitter.com/hashtag/hardwarewallet?src=hash&amp;ref_src=twsrc%5Etfw">#hardwarewallet</a> <a href="https://t.co/Q9sISLoKwo">pic.twitter.com/Q9sISLoKwo</a></p>&mdash; Andrea Franz (@gravityblast) <a href="https://twitter.com/gravityblast/status/1197191210244411393?ref_src=twsrc%5Etfw">November 20, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
+
+---
+
+...or just with a phone that a merchant wants to use as a point of sale:
+
+<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/RU8IN7kNSBQ" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
+---
+
+## The Keycard Applet
+
+When you receive the card the applet is installed but not initialized.
+This means that it doesn't contain any key, and it needs to be initialized to be able to sign transactions.
+During the initialization process we generate some secrets that we'll need
+later to use the card:
+
+* a pairing password needed to pair the card to a device.
+* a PIN needed to sign data and transactions (and for other commands).
+* a PUK needed to reset the PIN.
+
+After initialization the card is ready to be paired with a device using the secrets generated in the previous step.
+
+Once initialized, we can generate a new key with the [GENERATE KEY command](https://status.im/keycard_api/apdu/generatekey.html).
+In other cases, it's also possible to import a normal key, an extended key,
+or a seed derived from a mnemonic phrase following the [BIP39](https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki).
+
+Now that we have a master key, we can sign any 32 bytes of data with the derivation path we want
+after authenticating with the PIN generated during initialization.
+
+## The Cash Applet
+
+