CH01::Wallet Types: mention privacy; s/HWW/hardware signing device/

- Mention that mobile wallets and web wallets almost universally use
  remote servers for scanning, reducing privacy.

- Rename "hardware wallets" to "hardware signing devices".  In general,
  all these devices do is display info about an unsigned transaction to
  a user and then sign it if the user approves.  They need to be paired
  with other software that implements all of the other wallet behavior.
  We rename them accordingly and mention that the security and privacy
  of the wallet they pair with plays a role in the user's security and
  privacy.

ch01.asciidoc

@@ -200,24 +200,33 @@ Mobile wallet:: A mobile wallet is the most common type of Bitcoin
 wallet. Running on smart-phone operating systems such as Apple iOS and
 Android, these wallets are often a great choice for new users. Many are
 designed for simplicity and ease-of-use, but there are also fully
-featured mobile wallets for power users.
+featured mobile wallets for power users.  To avoid downloading and
+storing large amounts of data, most mobile wallets retrieve information
+from remote servers, reducing your privacy by disclosing information
+about your Bitcoin addresses and balances to third parties.
 
 Web wallet:: Web wallets are accessed through a web browser and store
 the user's wallet on a server owned by a third party. This is similar to
 webmail in that it relies entirely on a third-party server. Some of
 these services operate using client-side code running in the user's
 browser, which keeps control of the Bitcoin keys in the hands of the
-user. Most, however, present a compromise by taking control of the
-Bitcoin keys from users in exchange for ease-of-use. It is inadvisable
+user, although the user's dependence on the server still compromises
+their privacy. Most, however, take control of the Bitcoin keys from
+users in exchange for ease-of-use. It is inadvisable
 to store large amounts of bitcoin on third-party systems.
 
-Hardware wallet:: Hardware wallets are devices that operate a secure
-self-contained Bitcoin wallet on special-purpose hardware. They usually
-connect to a desktop or mobile device via USB cable or
-near-field-communication (NFC), and are operated with a web browser or
-accompanying software. By handling all Bitcoin-related operations on the
-specialized hardware, these wallets are considered very secure and
-suitable for storing large amounts of bitcoin.
+Hardware signing devices:: Hardware signing devices are devices that can
+store keys and sign transactions using a special-purpose hardware and
+software. They usually
+connect to a desktop, mobile, or web wallet via USB cable,
+near-field-communication (NFC), or a camera with QR codes.  By handling
+all Bitcoin-related operations on the specialized hardware, these
+wallets are less vulnerable to many types of attacks.  Hardware signing
+devices are sometimes called "hardware wallets", but they need to be
+paired with a full-featured wallet to send and receive transactions, and
+the security and privacy offered by that paired wallet plays a critical
+role in how much security and privacy the user obtains when using the
+hardware signing device.
 
 ===== Full-node vs. Lightweight
 Another way to categorize bitcoin wallets is by their degree of autonomy and how they interact with the Bitcoin network: