Determining the ideal length and strength for a secure passphrase

Selecting an appropriate passphrase is crucial for safeguarding your digital assets. A well-crafted passphrase enhances security by making unauthorized access significantly more challenging.


Why passphrase length and complexity matter

The strength of a passphrase is determined by its length and the randomness of its components. Longer passphrases with unpredictable elements are more resistant to brute-force attacks, where attackers systematically try all possible combinations to gain access.


When crafting a passphrase (up to 149 characters are possible), consider the following guidelines:

  • Random Word Sequences: Utilizing a series of random words can create strong passphrases. For instance, a five-word sequence from a curated word list provides substantial security. 
  • Character Combinations: If opting for a mix of uppercase and lowercase letters, numbers, and special characters, a minimum of 12 characters is advisable.

Evaluating passphrase security

The security of a passphrase can be quantified by the computational effort required to break it:

  • Entropy Measurement: Entropy, measured in bits, indicates the unpredictability of a passphrase. Higher entropy signifies greater security.
  • Breaking Cost: A passphrase with sufficient entropy would require significant computational resources and time to break, making unauthorized access economically unfeasible.

Best practices for creating strong passphrases

  1. Avoid Common Phrases: Steer clear of easily guessable phrases or quotes.
  2. Incorporate Complexity: Mix different character types to enhance security.
  3. Ensure Memorability: While complexity is vital, ensure the passphrase is memorable to avoid writing it down.

For a comprehensive guide on evaluating passphrase strength, refer to this detailed article from SatoshiLabs: Is your passphrase strong enough?