Edited ch04.asciidoc with Atlas code editor

ch04.asciidoc

@@ -606,11 +606,11 @@ BTC public key: 029ade3effb0a67d5c8609850d797366af428f4a0d5194cb221d807770a15228
 
 === Advanced Keys and Addresses
 
-In the following sections we will look at advanced forms of keys and addresses, such as encrypted private keys, script and multisignature addresses, vanity addresses, and paper wallets.
+((("keys and addresses", "advanced forms", id="KAadvanced04")))In the following sections we will look at advanced forms of keys and addresses, such as encrypted private keys, script and multisignature addresses, vanity addresses, and paper wallets.
 
 ==== Encrypted Private Keys (BIP-38)
 
-Private keys must remain secret. The need for _confidentiality_ of the private keys is a truism that is quite difficult to achieve in practice, because it conflicts with the equally important security objective of _availability_. Keeping the private key private is much harder when you need to store backups of the private key to avoid losing it. A private key stored in a wallet that is encrypted by a password might be secure, but that wallet needs to be backed up. At times, users need to move keys from one wallet to another—to upgrade or replace the wallet software, for example. Private key backups might also be stored on paper (see <<paper_wallets>>) or on external storage media, such as a USB flash drive. But what if the backup itself is stolen or lost? These conflicting security goals led to the introduction of a portable and convenient standard for encrypting private keys in a way that can be understood by many different wallets and bitcoin clients, standardized by Bitcoin Improvement Proposal 38  or BIP-38 (see <<appdxbitcoinimpproposals>>). 
+((("bitcoin improvement proposals", "Encrypted Private Keys (BIP38)")))((("keys and addresses", "advanced forms", "encrypted private keys")))Private keys must remain secret. The need for _confidentiality_ of the private keys is a truism that is quite difficult to achieve in practice, because it conflicts with the equally important security objective of _availability_. Keeping the private key private is much harder when you need to store backups of the private key to avoid losing it. A private key stored in a wallet that is encrypted by a password might be secure, but that wallet needs to be backed up. At times, users need to move keys from one wallet to another—to upgrade or replace the wallet software, for example. Private key backups might also be stored on paper (see <<paper_wallets>>) or on external storage media, such as a USB flash drive. But what if the backup itself is stolen or lost? These conflicting security goals led to the introduction of a portable and convenient standard for encrypting private keys in a way that can be understood by many different wallets and bitcoin clients, standardized by Bitcoin Improvement Proposal 38  or BIP-38 (see <<appdxbitcoinimpproposals>>). 
     
 BIP-38 proposes a common standard for encrypting private keys with a passphrase and encoding them with Base58Check so that they can be stored securely on backup media, transported securely between wallets, or kept in any other conditions where the key might be exposed. The standard for encryption uses the Advanced Encryption Standard (AES), a standard established by the National Institute of Standards and Technology (NIST) and used broadly in data encryption implementations for commercial and military applications. 
 
@@ -816,7 +816,7 @@ image::images/mbc2_0410.png[]
 .The bitcoinpaperwallet.com paper wallet with the private key concealed
 image::images/mbc2_0411.png[]
 
-Other designs feature additional copies of the key and address, in the form of detachable stubs similar to ticket stubs, allowing you to store multiple copies to protect against fire, flood, or other natural disasters.((("", startref="BCkeys04"))) 
+Other designs feature additional copies of the key and address, in the form of detachable stubs similar to ticket stubs, allowing you to store multiple copies to protect against fire, flood, or other natural disasters.((("", startref="BCkeys04")))((("", startref="KAadvanced04"))) 
 
 [[paper_wallet_spw]]
 .An example of a paper wallet with additional copies of the keys on a backup "stub"