BIP39 passphrase generator

BIP39 (Bitcoin Improvement Proposal 39) is a standard that defines how to generate a mnemonic sentence (a sequence of words) from a random value (entropy) and how to convert it into a binary seed.

The mnemonic sentence can be easily written down and remembered by humans, serving as a backup or recovery tool for cryptocurrency wallets.

BIP39 works by:

1. Generating a random sequence of bytes (entropy)
2. Creating a checksum of this entropy by taking the first few bits of its SHA256 hash
3. Appending the checksum to the entropy
4. Splitting the result into 11-bit segments
5. Mapping each segment to a word from a predefined wordlist (2048 words)

The result is a mnemonic phrase that can be used to deterministically generate private keys for cryptocurrency wallets.

A BIP39 seed is derived from the mnemonic phrase using PBKDF2 with HMAC-SHA512. This seed is typically 512 bits (64 bytes) and serves as the master seed for HD wallets (BIP32).

The optional passphrase (sometimes called the "25th word") provides additional security by making the seed derivation dependent on both the mnemonic and this passphrase.

For high-security applications like cryptocurrency wallets, it's best to generate mnemonics on an offline device using trusted software.

This online tool is provided for educational purposes and for non-critical applications. All processing is done locally in your browser, and no data is sent to any server.