The Foundation of Password Security
A strong password is your first line of defense against cybercriminals. It should be difficult for both humans and computers to guess, while remaining memorable enough for you to use effectively.
Key Characteristics of Strong Passwords
Length
Minimum: 12 characters
Recommended: 16+ characters
Length is the most important factor. Each additional character exponentially increases the time needed to crack your password.
Character Variety
Include: Upper & lowercase letters, numbers, symbols
Using different character types increases the possible combinations, making your password harder to crack.
Unpredictability
Avoid: Dictionary words, personal information, patterns
Random combinations are much stronger than predictable patterns or common words.
Password Entropy: The Science of Unpredictability
Password entropy is a measure of how unpredictable a password is. It's measured in bits, and the higher the entropy, the more secure the password. The formula for calculating entropy is:
E = L * log2(N)
- E is the entropy in bits.
- L is the length of the password.
- N is the number of possible characters in the character set.
Character Set Size (N)
- Lowercase letters only: 26
- + Uppercase letters: 52
- + Numbers: 62
- + Symbols: 94
Time to Crack Examples
| Password Length | Character Set | Entropy (bits) | Time to Crack (at 1B guesses/sec) |
|---|---|---|---|
| 8 | Lowercase only | 37.6 | Seconds |
| 8 | All character types | 52.5 | Hours |
| 12 | All character types | 78.8 | Centuries |
| 16 | All character types | 105.1 | Millennia |
Common Attack Vectors
Understanding how attackers try to compromise passwords can help you create stronger defenses.
Brute Force Attacks
This method involves trying every possible combination of characters until the correct password is found. The longer and more complex your password, the longer a brute force attack will take.
Dictionary Attacks
Attackers use lists of common words, phrases, and previously compromised passwords to guess your password. This is why using dictionary words is so risky.
Rainbow Table Attacks
A rainbow table is a precomputed table for reversing cryptographic hash functions. If a website stores password hashes (a more secure method than storing plain text), a rainbow table can be used to find the password that corresponds to a given hash.
Password vs. Passphrase
A passphrase is a sequence of words, like a short sentence. While a long, random password is the most secure option, a long passphrase can be a good alternative if it's easier for you to remember.
Example Passphrase
correct-horse-battery-staple
This passphrase is 28 characters long and has high entropy, making it very secure.
How Password Managers Help
A password manager is a tool that generates, stores, and manages your passwords for you. It can help you:
- Generate long, random, and unique passwords for every account.
- Store your passwords in an encrypted vault.
- Automatically fill in your passwords when you log in to websites.
Frequently Asked Questions (FAQ)
Is a longer password always better?
Yes, length is the most important factor in password strength. Each additional character exponentially increases the time it would take to crack your password.
Should I change my passwords regularly?
The current recommendation from NIST is to only change your password if you suspect it has been compromised. Frequent password changes can lead to weaker passwords as people tend to make small, predictable changes.
Are password managers secure?
Reputable password managers use strong encryption to protect your data. The main risk is a weak master password, so make sure your master password is very strong and memorable.