diff --git a/ch04.asciidoc b/ch04.asciidoc index 20bd6ba0..616969ef 100644 --- a/ch04.asciidoc +++ b/ch04.asciidoc @@ -1207,68 +1207,6 @@ 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) - -((("bitcoin improvement proposals", "Encrypted Private Keys -(BIP-38)")))((("keys and addresses", "advanced forms", "encrypted -private keys")))((("public and private keys", "encrypted private -keys")))((("passwords", "encrypted private keys")))((("security", -"passwords")))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 <>) 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 BIP-38 (see <>). - -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 NIST and used broadly in data encryption -implementations for commercial and military applications. - -A BIP-38 encryption scheme takes as input a bitcoin private key, usually -encoded in the WIF, as a Base58Check string with the prefix of "5." -Additionally, the BIP-38 encryption scheme takes a passphrase—a long -password—usually composed of several words or a complex string of -alphanumeric characters. The result of the BIP-38 encryption scheme is a -Base58Check-encoded encrypted private key that begins with the prefix -+6P+. If you see a key that starts with +6P+, 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 BIP-38-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 BIP-38 keys. - -The most common use case for BIP-38 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 BIP-38 -encrypted private keys is incredibly secure and a great way to create -offline bitcoin storage (also known as "cold storage"). - -Test the encrypted keys in <> using bitaddress.org to see -how you can get the decrypted key by entering the passphrase. - -[[table_4-10]] -.Example of BIP-38 encrypted private key -|======= -| *Private Key (WIF)* | 5J3mBbAH58CpQ3Y5RNJpUKPE62SQ5tfcvU2JpbnkeyhfsYB1Jcn -| *Passphrase* | MyTestPassphrase -| *Encrypted Key (BIP-38)* | 6PRTHL6mWa48xSopbU1cKrVjpKbBZxcLRRCdctLJ3z5yxE87MobKoXdTsJ -|======= - [[p2sh_addresses]] ==== Pay-to-Script Hash (P2SH) and Multisig Addresses