What is a BIP39 Passphrase?

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BIP-32 and BIP-39: Simplifying Bitcoin Wallet Key Management

In the early stages of Bitcoin, there were no user-friendly methods available for remembering Bitcoin wallet keys or creating paper backups with mnemonic words. To address this challenge, two standards, namely BIP-32 and BIP-39, were developed. These standards have gained widespread adoption and will be the focus of this discussion.

The concept of BIP-32, known as hierarchical deterministic wallets, was proposed and eventually embraced as a solution. Subsequently, an extension called BIP-39 was introduced.

What is BIP-39?

BIP-39 defines a mechanism for converting a random list of bytes (known as a seed) into a list of human-readable words that are easy to memorize and write down. Unlike raw binary or hexadecimal representations, the word list provides a more readable format, enabling better human management and storage of the seed.

The BIP-32 standard, also referred to as hierarchical deterministic wallets, outlines the process of deriving or generating a key pair from a seed. This key pair is used to secure your cryptocurrency assets. The derivation path, a crucial element, determines each unique key pair. As a result, a single seed can be utilized to generate and manage multiple separate accounts.

The " BIP39 Passphrase " is an optional and advanced security feature that enables the creation of a new wallet by adding an additional passphrase to the existing 24-word Secret Recovery Phrase.
Originating from the 39th Bitcoin Improvement Proposal (BIP) , this feature has become a standard within the wider cryptocurrency community. Think of it as an extra word, the 25th word, added to your seed or Secret Recovery Phrase.

WHY?

The "BIP39 Passphrase" is primarily used to provide a concept known as "Plausible Deniability." This term, as defined by Wikipedia, refers to the intentional arrangement of circumstances that allows individuals to potentially avoid taking responsibility for their future actions or knowledge.

In the context of cryptocurrency wallets, the BIP39 Passphrase offers an additional layer of security and privacy. By creating multiple wallets with different passphrases, it becomes possible to have plausible deniability regarding the existence or ownership of specific wallets. In the event that someone gains unauthorized access to one of the wallets or demands access, users can provide an alternative passphrase that leads to a different wallet, keeping their other assets secure and hidden.

This feature provides users with an added level of control and protection, ensuring that their cryptocurrency holdings remain private and safeguarded.

"BIP39" is named as such because it is the 39th Bitcoin Improvement Proposal (BIP) within the cryptocurrency community. The BIPs are technical design documents introduced to propose improvements and changes to the Bitcoin protocol. BIP39 specifically addresses the generation of mnemonic codes for deterministic keys.

Advantages of BIP39

1. Human Readability: BIP39 allows for the representation of private keys in a human-readable format using mnemonic words. This makes it easier for individuals to recognize and remember their keys.

2. Multiple Accounts: BIP39 enables the management of multiple separate accounts derived from the same seed. By modifying the derivation path, different private keys can be generated.

3. Plausible Deniability: BIP39 offers a feature known as plausible deniability, which adds an extra layer of security.

4. Security Benefits of Passphrase: With BIP39, the passphrase adds an additional layer of security.

5. Plausible Deniability and Hidden Wallets: The combination of passphrase and plausible deniability allows for the creation of hidden wallets.

6. Ease of Passphrase Generation: Passphrases can be generated freely in combination with the recovery seed, providing flexibility and convenience.

By leveraging BIP39 and its associated features, individuals can enhance the security, manageability, and privacy of their cryptocurrency wallets.

How likely is your BIP39 seed phrase to be guessed?

The likelihood of guessing a BIP39 seed phrase constructed from random inputs is extremely low, bordering on practically impossible. A BIP39 seed phrase typically consists of 12 or 24 words chosen from a predefined list of 2048 words.

To put this into perspective, the estimated number of atoms in the known universe is around 10^80. The number of possible BIP39 seed phrases is of a similar magnitude, making it virtually impossible to guess a specific seed phrase through random attempts.

Here's a step-by-step guide to creating and adding a BIP39 passphrase:

1. Understand BIP39: BIP39 is a standard that defines how mnemonic phrases (a sequence of words) are generated from an entropy value. It also allows for the addition of a passphrase to enhance security.

2. Generate a mnemonic phrase: Use a BIP39-compliant tool or library to generate a random mnemonic phrase.

3. Choose a passphrase: Select a strong passphrase that you will remember but is difficult for others to guess.

4. Combine the mnemonic phrase and passphrase: Concatenate the mnemonic phrase and the passphrase together.

5. Derive a seed: Use a cryptographic function, such as PBKDF2 or HMAC-SHA512, to derive a seed from the combined mnemonic phrase and passphrase.

6. Derive private keys: Utilize the seed to derive private keys following the BIP32 and BIP44 standards. These private keys can be used to generate addresses and perform cryptographic operations within a hierarchical deterministic wallet.