How to Create a Strong Password — Entropy, Passphrases & Security

Introduction

In today's digital world, your password is the first—and often only—line of defence for your online identity. Yet most people still use weak, predictable, or reused passwords, making them easy targets for hackers.

Why Password Security Matters

Identity theft prevention across email, banking, social accounts
Financial protection from unauthorised access
Privacy safeguarding of personal data and communications
Professional security for work accounts and sensitive information

The Modern Password Challenge

Learning how to create a strong password isn't just about complexity—it's about understanding:

Randomness and entropy (measurable security)
Length vs complexity trade-offs
Modern security practices (passphrases, password managers)
Practical implementation for daily use

This guide demystifies password entropy, compares generation methods, and gives you actionable strategies to protect your accounts from compromise.

The Science of Password Strength: It’s All About Entropy

Password strength isn’t subjective—it’s measurable using entropy, expressed in bits. Entropy quantifies the number of guesses an attacker would need to crack your password through brute force.

The Entropy Formula

For a randomly generated password:

H = L × log₂(N)
Where:

H = Entropy (bits)
L = Password length (characters)
N = Size of the character set

Character set examples:

Lowercase letters: N = 26 → ~4.7 bits/char
Upper + lower + digits + symbols: N ≈ 94 → ~6.55 bits/char

Example:
A 12-character password using all character types:
H = 12 × log₂(94) ≈ 78.6 bits
This would take centuries to crack with current technology.

Passphrases: Strong and Memorable

Instead of Xk9#q!Lm2$vP, consider glacier-trombone-velvet-compass.

Uses 4 random words from a 7,776-word list (like EFF’s)
Entropy: 4 × log₂(7776) ≈ 51.6 bits
Longer (28+ characters), easier to remember, and still highly secure

💡 Rule of thumb: Length > Complexity. A 20-character lowercase password (H ≈ 94 bits) is stronger than a 10-character complex one (H ≈ 65 bits).

Why Human-Created Passwords Fail

People reuse patterns:

Password123!
John1985
qwertyuiop

These are in every hacker’s dictionary. Even with symbols, they offer below 30 bits of entropy—crackable in seconds.

Essential Security Practices

1. Use a Password Manager

Tools like Bitwarden, 1Password, or KeePass:

Generate and store unique, strong passwords
Auto-fill login forms
Sync across devices
You only remember one master password (make it a strong passphrase!)

2. Enable Two-Factor Authentication (2FA)

Add a second layer:

Authenticator app (Google Authenticator, Authy)
Security key (YubiKey)
SMS (least secure, but better than nothing)

Even if your password leaks, 2FA blocks unauthorised access.

3. Never Reuse Passwords

One breach = all accounts compromised. A password manager solves this.

4. Treat Security Questions as Passwords

“Mother’s maiden name?” → Answer with a random string like 7m$Kp!qL and store it in your manager.

Common Pitfalls & Misconceptions

❌ “My password has a symbol, so it’s strong.” → Length matters more.
❌ “I’ll just change one letter each time.” → Predictable patterns are crackable.
❌ “I can remember all my passwords.” → Humans can’t reliably manage 100+ unique passwords.
✅ “I use a 6-word passphrase for my email.” → Excellent choice.

When to Use Which Method

| Scenario | Recommended Approach | |--------|---------------------| | Email, banking, social media | 20+ char random password + 2FA | | Master password for manager | 5–6 word random passphrase | | Low-risk forum accounts | Unique 12+ char password | | Accounts with silly limits (e.g., 8 chars, no symbols) | Max out length with upper/lower/numbers |

Build Your Own Secure Passwords

1. Calculate Entropy

For each, compute entropy (H = L × log₂(N)):

hello123 (8 chars, lower + digits → N=36) → H ≈ 8 × 5.17 = 41.4 bits
Tr0ub4dor&3 (12 chars, mixed → N=94) → H ≈ 78.6 bits
correct-horse-battery-staple (4 words, V=7776) → H ≈ 51.6 bits

Despite being longer, the passphrase has less entropy than the random 12-char password—but it’s far more usable.

2. Generate Real Examples

Use a trusted generator or dice:

Random: kL9$mQ!vR2#pN8&wX4
Passphrase: sunset-marmalade-rocket-ladle

3. Security Audit

Review your top 5 accounts:

Is the password unique?
Is it at least 12 characters?
Is 2FA enabled?
Is it stored in a password manager?

Fix any “no” answers immediately.

4. Create Your Master Passphrase

Roll physical dice or use EFF’s wordlist:

Pick 5 words: e.g., tundra, pickle, engine, velvet, goblin
Combine: tundra-pickle-engine-velvet-goblin
Memorise it. This is your vault key.

How long should my password be?

Minimum: 12 characters for low-risk sites
Recommended: 16–20+ characters for email, banking, cloud storage
Passphrases: 4–6 random words

Are password generators safe?

Yes—if they run locally in your browser (like this one). Avoid generators that send data to servers. Even better: use your password manager’s built-in generator.

What if a site doesn’t allow long passwords?

Some outdated systems cap at 12–16 characters or ban symbols. In that case:

Use maximum allowed length
Combine upper, lower, and numbers
Still make it random (not Password1)

Can hackers really crack my password?

Yes—if it’s weak. Modern tools can test 100 billion guesses per second. A password with below 50 bits of entropy is vulnerable. Strong, unique passwords render this ineffective.

Is a passphrase really secure?

Yes—if the words are randomly selected. Don’t use song lyrics, quotes, or personal info. Use a published wordlist (like EFF’s) and pick words by dice or a trusted generator.

What’s the #1 thing I should do today?

Install a password manager and enable 2FA on your email. Your email is the “master key” to reset all other passwords—protect it fiercely.

Should I change passwords regularly?

Only if:

The service was breached
You suspect compromise
You’ve been reusing passwords
Otherwise, frequent changes encourage weaker passwords. Focus on uniqueness and strength instead.

Related Calculators

Binary Converter – Understand the binary basis of digital security
Scientific Calculator – Has random number generation functions

Call to Action

Your digital life is worth protecting. Generate your first strong password today, store it in a manager, and enable 2FA. You’ve just made yourself a much harder target.