Clear DefinitionsBIP-39
2 min read
Pronunciation
[bip thur-tee nahyn]
Analogy
Think of BIP-39 as the official dictionary and instruction manual for creating a secret recovery sentence (your seed phrase). Instead of trying to remember a super long and complex password (the raw seed), BIP-39 lets you use a list of simple words from this dictionary. If you follow its rules, you can reliably recreate your complex password anytime just by remembering or securely storing those words.
Definition
Bitcoin Improvement Proposal 39 (BIP-39) is a technical standard that describes the implementation of a mnemonic code or mnemonic sentence – a group of human-readable words – for the generation of deterministic wallet seeds. It provides a user-friendly way to back up and recover cryptocurrency wallets.
Key Points Intro
BIP-39 standardizes the creation of seed phrases, making wallet backup and recovery more accessible and interoperable.
Key Points
Mnemonic Generation: Defines a method for converting random entropy into a sequence of human-readable words.
Wordlists: Specifies official wordlists for various languages (e.g., English list has 2048 words).
Seed Derivation: Describes how to convert the mnemonic phrase (and an optional passphrase) into a binary seed, typically 512 bits, suitable for BIP-32 HD wallets.
Interoperability: Allows users to recover wallets created with one BIP-39 compatible wallet using another compatible wallet.
Example
When setting up a new cryptocurrency wallet, the software generates a 12-word mnemonic phrase like "lemon zebra acquire engine recall jump fine december trophy visa word pulp" according to the BIP-39 standard. The user writes these words down. This phrase can later be used with a key derivation function (PBKDF2) to produce a 512-bit seed, which then serves as the root for a BIP-32 HD wallet.
Technical Deep Dive
BIP-39 process starts with generating initial entropy (128 to 256 bits). A checksum is derived from the SHA256 hash of the entropy and appended to it. This combined sequence is then split into 11-bit chunks, each chunk representing an index from 0 to 2047, corresponding to a word in the BIP-39 wordlist. The resulting sequence of words is the mnemonic phrase. To convert this mnemonic to a binary seed, the PBKDF2 function is used with the mnemonic as the password and the string "mnemonic" + optional_user_supplied_passphrase as the salt, using 2048 rounds of HMAC-SHA512 to produce a 512-bit seed.
Security Warning
The BIP-39 mnemonic phrase (seed phrase) must be kept extremely secure. Anyone who gains access to it can derive the wallet seed and steal all associated funds. Avoid storing it digitally or sharing it. The optional passphrase adds security but must also be remembered or stored securely; losing it means losing access to funds generated with it.
Caveat
While BIP-39 is widely adopted, users should ensure their wallet explicitly states BIP-39 compatibility for recovery. The optional passphrase (sometimes called the "25th word") creates an entirely different seed; if used, it must be remembered or stored as securely as the mnemonic itself. Forgetting it is equivalent to losing the seed.
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