Update ch01.asciidoc

ch01.asciidoc

@@ -135,6 +135,11 @@ Alice is now ready to start using her new bitcoin wallet. ((("", startref="GSqui
 
 Alice clicks on the _Recieve_ button, which displays a QR code along with a bitcoin address. The QR code is the square with a pattern of black and white dots. Next to the wallet's bitcoin address is a QR code, a form of barcode that contains the same information in a format that can be scanned by a smartphone camera.  Alice can copy the bitcoin address onto her clipboard by tapping it. In most wallets, tapping the QR code will also magnify it, so that it can be more easily scanned by a smartphone camera. Of note, when recieving fund from a new mobile wallet for the first time, many wallets will often re-verify that you have indeed secured your mneumonic phrase. This can range from a simple prompt to requiring the user to manually re-enter the phrase.  
 
+[TIP]
+====
+((("addresses", "security of")))((("security", "bitcoin addresses")))Bitcoin addresses start with 1, 3, or bc1. Like email addresses, they can be shared with other bitcoin users who can use them to send bitcoin directly to your wallet. There is nothing sensitive, from a security perspective, about the bitcoin address. It can be posted anywhere without risking the security of the account. Unlike email addresses, you can create new addresses as often as you like, all of which will direct funds to your wallet. In fact, many modern wallets automatically create a new address for every transaction to maximize privacy. A wallet is simply a collection of addresses and the keys that unlock the funds within.
+====
+
 [[getting_first_bitcoin]]
 ==== Getting Your First Bitcoin