What is BIP39?

Bitcoin Improvement Proposal 39, or BIP39, is a protocol that was introduced as a means to generate deterministic wallets. It's a method for creating a human-readable mnemonic sentence – easy to read and write – from random data that serves as a backup to recover your wallet. It is an open-source protocol that is widely adopted in the cryptocurrency industry including Trezor.
 

In the world of cryptography and digital assets, one of the most critical aspects of managing digital assets is the ability to restore them in case of device loss or failure. BIP39 provides an excellent solution for this issue, as it presents a more user-friendly method of backup compared to random strings of characters.
 

Where did BIP39 come from?

BIP39 was introduced by Marek Palatinus, Pavol Rusnak, Aaron Voisine, and Sean Bowe in 2013 to propose a standardized method of generating mnemonic sentences for deterministic wallets. The idea behind BIP39 was to create a process that could be universally adopted, ensuring cross-compatibility between different wallets. 
 

How does BIP39 work? 

BIP39 works by generating a mnemonic sentence – a group of easy-to-remember words – from a random number, usually a 128 to 256-bit random number. The more bits, the more secure it is, but also the more words in the mnemonic sentence.
 

Here's a simplified version of how the process works:
 

1. Generate a random number.
2. Convert the random number to binary.
3. Create a checksum of the binary version.
4. Append the checksum to the end of the original binary number.
5. Divide the binary sequence into groups of 11 bits.
6. Each 11-bit group corresponds to a word from a predetermined list of 2048 words.
7. The resulting list of words is your mnemonic phrase.

This mnemonic phrase can be used to recover the original random number and, by extension, a user's private keys. This method is much more user-friendly than expecting users to keep track of a complex sequence of letters and numbers.
 

BIP39 and Trezor

Trezor wallets employ BIP39 for the recovery seed phrases. When you initialize your Trezor device, it generates a unique 12, 18, or 24-word recovery seed. This seed is a representation of your private keys and is essential for restoring your wallet's information in case your device is lost, stolen, or damaged.
 

In order to enhance security, Trezor does not store your recovery seed. Therefore, it's critical for you to write down your recovery seed and store it in a safe location. In case you need to recover your wallet, you can enter this recovery seed into a new Trezor device or any other wallet that supports BIP39, enabling you to access your funds.
 

BIP39 has become a crucial part of Trezor's security protocol, and it is used alongside other BIPs like BIP32 (Hierarchical Deterministic Wallets) and BIP44 (Multi-Account Hierarchy for Deterministic Wallets) to provide an optimal security model for cryptocurrency users.
 

BIP39 is a significant development in the world of crypto-assets, and Trezor, among many others, has fully adopted this proposal to ensure an efficient and user-friendly security mechanism for their hardware wallets.