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@ -824,7 +824,7 @@ In the following sections we will look at advanced forms of keys and addresses,
BIP0038 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)"))) 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.
((("Wallet Import Format (WIF)","for BIP0038 encryption")))A BIP0038 encryption scheme takes as input a bitcoin private key, usually encoded in the Wallet Import Format (WIF), as a Base58Check string with a prefix of "5". Additionally, the BIP0038 encryption scheme takes a passphrase—a long password—usually composed of several words or a complex string of alphanumeric characters. The result of the BIP0038 encryption scheme is a Base58Check-encoded encrypted private key that begins with the prefix +6P+. If you see a key that starts with +6P+, that means it is encrypted and requires a passphrase in order to convert (decrypt) it back into a WIF-formatted private key (prefix +5+) that can be used in any wallet. Many wallet applications now recognize BIP0038 encrypted private keys and will prompt the user for a passphrase to decrypt and import the key. Third-party applications, such as the incredibly useful browser-based http://bitaddress.org/[bitaddress.org] (Wallet Details tab), can be used to decrypt BIP0038 keys.
((("Wallet Import Format (WIF)","for BIP0038 encryption")))A BIP0038 encryption scheme takes as input a bitcoin private key, usually encoded in the Wallet Import Format (WIF), as a Base58Check string with a prefix of "5". Additionally, the BIP0038 encryption scheme takes a passphrase—a long password—usually composed of several words or a complex string of alphanumeric characters. The result of the BIP0038 encryption scheme is a Base58Check-encoded encrypted private key that begins with the prefix +6P+. If you see a key that starts with +6P+, that means it is encrypted and requires a passphrase in order to convert (decrypt) it back into a WIF-formatted private key (prefix +5+) that can be used in any wallet. Many wallet applications now recognize BIP0038-encrypted private keys and will prompt the user for a passphrase to decrypt and import the key. Third-party applications, such as the incredibly useful browser-based http://bitaddress.org[Bit Address] (Wallet Details tab), can be used to decrypt BIP0038 keys.
((("paper wallets","BIP0038 encryption and")))The most common use case for BIP0038 encrypted keys is for paper wallets that can be used to back up private keys on a piece of paper. As long as the user selects a strong passphrase, a paper wallet with BIP0038 encrypted private keys is incredibly secure and a great way to create offline bitcoin storage (also known as "cold storage").
@ -840,13 +840,13 @@ Test the encrypted keys in <<table_4-10>> using((("bitaddress.org"))) bitaddress
[[p2sh_addresses]]
==== Pay-to-Script-Hash (P2SH) and Multi-Sig Addresses
==== Pay-to-Script Hash (P2SH) and Multi-Sig Addresses
((("addresses, bitcoin","multi-sig addresses")))((("addresses, bitcoin","Pay-to-Script-Hash (P2SH)")))((("multi-sig addresses")))((("Pay-to-Script-Hash (P2SH)")))As we know, traditional bitcoin addresses begin with the number “1” and are derived from the public key, which is derived from the private key. Although anyone can send bitcoin to a “1” address, that bitcoin can only be spent by presenting the corresponding private key signature and public key hash.
((("addresses, bitcoin","multi-sig addresses")))((("addresses, bitcoin","Pay-to-Script Hash (P2SH)")))((("multi-sig addresses")))((("Pay-to-Script Hash (P2SH)")))As we know, traditional bitcoin addresses begin with the number “1” and are derived from the public key, which is derived from the private key. Although anyone can send bitcoin to a “1” address, that bitcoin can only be spent by presenting the corresponding private key signature and public key hash.
Bitcoin addresses that begin with the number “3” are pay-to-script-hash (P2SH) addresses, sometimes erroneously called multi-signature or multi-sig addresses. They designate the beneficiary of a bitcoin transaction as the hash of a script, instead of the owner of a public key. The feature was introduced in January 2012 with Bitcoin Improvement Proposal 16, or BIP0016 (see <<bip0016>>), and is being widely adopted because it provides the opportunity to add functionality to the address itself. Unlike transactions that "send" funds to traditional “1” bitcoin addresses, also known as((("BIP0016")))((("Pay-to-Public-Key-Hash (P2PKH)"))) pay-to-public-key-hash (P2PKH), funds sent to “3” addresses require something more than the presentation of one public key hash and one private key signature as proof of ownership. The requirements are designated at the time the address is created, within the script, and all inputs to this address will be encumbered with the same requirements.
Bitcoin addresses that begin with the number “3” are pay-to-script hash (P2SH) addresses, sometimes erroneously called multi-signature or multi-sig addresses. They designate the beneficiary of a bitcoin transaction as the hash of a script, instead of the owner of a public key. The feature was introduced in January 2012 with Bitcoin Improvement Proposal 16, or BIP0016 (see <<bip0016>>), and is being widely adopted because it provides the opportunity to add functionality to the address itself. Unlike transactions that "send" funds to traditional “1” bitcoin addresses, also known as((("BIP0016")))((("Pay-to-Public-Key-Hash (P2PKH)"))) pay-to-public-key-hash (P2PKH), funds sent to “3” addresses require something more than the presentation of one public key hash and one private key signature as proof of ownership. The requirements are designated at the time the address is created, within the script, and all inputs to this address will be encumbered with the same requirements.
A pay-to-script-hash address is created from a transaction script, which defines who can spend a transaction output (for more detail, see <<p2sh>>). Encoding a pay-to-script hash address involves using the same double-hash function as used during creation of a bitcoin address, only applied on the script instead of the public key:
A pay-to-script hash address is created from a transaction script, which defines who can spend a transaction output (for more detail, see <<p2sh>>). Encoding a pay-to-script hash address involves using the same double-hash function as used during creation of a bitcoin address, only applied on the script instead of the public key:
----
script hash = RIPEMD160(SHA256(script))
@ -868,7 +868,7 @@ We will explore how to create transactions that spend funds from P2SH (and multi
==== Vanity Addresses
((("addresses, bitcoin","vanity", id="ix_ch04-asciidoc26", range="startofrange")))((("vanity addresses", id="ix_ch04-asciidoc27", range="startofrange")))Vanity addresses are valid bitcoin addresses that contain human-readable messages. For example, 1LoveBPzzD72PUXLzCkYAtGFYmK5vYNR33 is a valid address that contains the letters forming the word "Love" as the first four Base-58 letters. Vanity addresses require generating and testing billions of candidate private keys, until one derives a bitcoin address with the desired pattern. Although there are some optimizations in the vanity generation algorithm, the process essentially involves picking a private key at random, deriving the public key, deriving the bitcoin address, and checking to see if it matches the desired vanity pattern, repeating billions of times until a match is found.
((("addresses, bitcoin","vanity", id="ix_ch04-asciidoc26", range="startofrange")))((("vanity addresses", id="ix_ch04-asciidoc27", range="startofrange")))Vanity addresses are valid bitcoin addresses that contain human-readable messages. For example, +1LoveBPzzD72PUXLzCkYAtGFYmK5vYNR33+ is a valid address that contains the letters forming the word "Love" as the first four Base-58 letters. Vanity addresses require generating and testing billions of candidate private keys, until one derives a bitcoin address with the desired pattern. Although there are some optimizations in the vanity generation algorithm, the process essentially involves picking a private key at random, deriving the public key, deriving the bitcoin address, and checking to see if it matches the desired vanity pattern, repeating billions of times until a match is found.
Once a vanity address matching the desired pattern is found, the private key from which it was derived can be used by the owner to spend bitcoins in exactly the same way as any other address. Vanity addresses are no less or more secure than any other address. They depend on the same Elliptic Curve Cryptography (ECC) and Secure Hash Algorithm (SHA) as any other address. You can no easier find the private key of an address starting with a vanity pattern than you can any other address.