Every year, security researchers publish lists of the most commonly used passwords. And every year, â123456,â âpassword,â and âqwertyâ appear near the top. Despite decades of warnings, people continue creating weak passwordsâand attackers continue exploiting them.
As someone who has spent years researching both sides of this equation, I can tell you that the gap between a crackable password and an uncrackable one often comes down to a few simple principles that most people never learn. Let me share the security professionalâs approach to creating credentials that truly resist attack.
How Hackers Actually Crack Passwords
Before discussing password creation, you need to understand what youâre defending against. Hollywood depicts hackers as geniuses who somehow âguessâ passwords, but real password cracking is methodical and surprisingly effective against weak credentials.
The Breach-First Reality
Most password attacks donât happen against live login pages. Instead, attackers obtain massive databases of encrypted (hashed) passwords from data breaches, then work offline to crack them without rate limits or detection.
When a service stores your password, they donât keep it in plain text. They apply a mathematical function called a hash that converts your password into a seemingly random string. When you log in, your entered password gets hashed and compared to the stored hash.
The security assumption is that hashes canât be reversed. While technically true, attackers donât need to reverse themâthey can hash billions of guesses and compare results until they find a match.
Types of Cracking Attacks
Dictionary attacks: Attackers start with lists of known passwords from previous breaches, common words, phrases, and predictable patterns. These lists often contain billions of entries and catch a surprising percentage of passwords immediately.
Rule-based attacks: Attackers apply common modifications to dictionary words: capitalizing the first letter, adding numbers at the end, replacing letters with similar-looking numbers. âPasswordâ becomes âP@ssw0rd1!â through predictable transformations.
Brute force attacks: For passwords that survive dictionary and rule-based attacks, computers systematically try every possible combination. Modern GPUs can test tens of billions of combinations per second.
Hybrid attacks: Combinations of the above, often informed by patterns learned from previously cracked passwords.
Cracking Speed in 2026
Current high-end consumer hardware can test approximately:
- 100 billion MD5 hashes per second
- 35 billion SHA-1 hashes per second
- 5 billion bcrypt hashes per second (much slower due to intentional design)
This means an 8-character password using only lowercase letters (26^8 = 208 billion combinations) can be cracked against MD5 in roughly two seconds. Even against stronger hash functions, short passwords fall quickly.
The Science of Password Strength: Understanding Entropy
Security professionals measure password strength in bits of entropy. This quantifies how many possible passwords exist given a particular length and character set.
Calculating Entropy
Entropy equals the logarithm (base 2) of the number of possible combinations:
Bits = log2(character pool ^ length)
For a 12-character password using lowercase, uppercase, numbers, and symbols (95 printable ASCII characters):
Bits = log2(95^12) = approximately 79 bits of entropy
Each additional bit doubles the number of possible passwords. A 79-bit password has 2^79 possible valuesâmore than 600 sextillion combinations.
What Entropy Levels Mean Practically
Under 40 bits: Crackable within minutes to hours on consumer hardware. Unacceptable for any important account.
40-60 bits: May resist casual attacks but vulnerable to determined attackers with time. Adequate only for low-value accounts.
60-80 bits: Resists current cracking capabilities when combined with strong hash functions. Appropriate for most accounts.
80-100 bits: Provides comfortable margin against future hardware advances. Recommended for high-value accounts.
Over 100 bits: Essentially uncrackable with any foreseeable technology.
Why Length Beats Complexity
Adding character types increases entropy linearly, but adding length increases it exponentially.
Consider:
- 8 characters, lowercase only (26 chars): 37 bits
- 8 characters, all types (95 chars): 52 bits (15-bit improvement)
- 12 characters, lowercase only: 56 bits (19-bit improvement over 8 mixed)
- 16 characters, lowercase only: 75 bits (beats 8 mixed by 23 bits)
Length provides more security improvement than complexity. A long password using only lowercase letters is often stronger than a short password using all character types.
The Human Problem: Why Random Matters
Understanding entropy is necessary but not sufficient. The calculations above assume truly random selection. Human-generated ârandomâ passwords routinely fall far short.
Predictable Patterns We All Use
Researchers analyzing millions of leaked passwords have found remarkably consistent patterns:
- The first character is capitalized roughly 90% of the time when passwords contain capitals
- Numbers appear at the end roughly 80% of the time
- The most common number sequence is â1â or â123â
- Character substitutions follow predictable mappings: @ for a, 3 for e, 0 for o
- Password lengths cluster heavily at minimum requirements (8) and round numbers (10, 12)
These patterns dramatically reduce the actual entropy of human-chosen passwords. A password that appears to have 60 bits of entropy based on character pool and length might effectively have 30 bits when human patterns are accounted for.
The Only Solution: True Randomness
To achieve advertised entropy levels, you must eliminate human choice from password generation. This means using a cryptographically secure random number generatorâthe same kind of randomness used in encryptionâto select every character.
Our password generator uses your browserâs Web Crypto API to achieve genuinely random selection. Unlike JavaScriptâs Math.random() function, which produces pseudo-random numbers with predictable patterns, cryptographic randomness is suitable for security applications.
Creating Uncrackable Passwords: Practical Guidelines
Armed with this understanding, here are concrete recommendations for different account types.
For Your Most Critical Accounts
High-value targetsâprimary email, financial accounts, password manager master passwordâdeserve maximum protection.
Recommendation: 20+ character passwords using all character types (uppercase, lowercase, numbers, symbols), generated by a cryptographic random source.
Entropy: 130+ bits, providing centuries of protection against any conceivable attack.
Memorization: Donât try. Store these in your password manager or write them down in a secure physical location.
For Important Personal Accounts
Social media, shopping accounts, subscriptions with stored payment methods.
Recommendation: 16-character passwords using all character types, randomly generated.
Entropy: Approximately 105 bits, far exceeding cracking capabilities.
Storage: Password manager.
For Low-Risk Accounts
Accounts where breach would cause minimal harm and that require no payment information.
Recommendation: 12-character passwords using at least three character types.
Entropy: 75+ bits, adequate protection.
Storage: Password manager ensures uniqueness even for low-priority accounts.
For Accounts Requiring Memorization
Some credentialsâsuch as your password managerâs master passwordâyou must actually remember.
Recommendation: Use a passphrase of 4-5 randomly selected words, optionally with numbers or symbols between them.
Example format: word-word-word-number-word Approximate entropy: 65-80 bits depending on word list size and variations.
Why this works: Words are more memorable than character sequences, and random word combinations resist dictionary attacks that check common phrases.
Important: The words must be randomly selected, not personally meaningful phrases. âcorrect-horse-battery-stapleâ from the famous xkcd comic is not secure because itâs been published globally.
The Critical Role of Uniqueness
Even an extraordinarily strong password provides zero protection if you use it on multiple accounts.
The Credential Stuffing Threat
When any service suffers a breach, attackers harvest credentials and test them against other services. If your email-password combination from a minor forum breach also works on your bank account, attackers will find this within hours.
This attackâcalled credential stuffingâsucceeds approximately 0.1-2% of the time on average across large credential lists. When billions of credentials are tested, that percentage translates to millions of compromised accounts.
One Password Per Account, No Exceptions
Every account needs a unique password. With a password manager, this costs you nothingâyouâre not memorizing these passwords anyway. Let the generator create completely unique credentials for every service.
If you discover a password was involved in a breach, you only need to change that one password rather than every account where youâve used it.
Common Mistakes to Avoid
Even security-conscious users fall into patterns that weaken their protection.
Mistake 1: Thinking Common Substitutions Help
âP@ssw0rdâ is not secure. Neither is âS3cur1ty!â or any variation that simply swaps letters for similar-looking numbers or symbols. Cracking tools include these substitutions in their first attempts.
Mistake 2: Adding Predictable Sequences
Appending â123â or â!â to satisfy complexity requirements is so common that attackers test these patterns automatically. Your âMySecurePassword123!â is not meaningfully different from âmysecurepasswordâ to a modern cracking tool.
Mistake 3: Using Personal Information
Your name, birthday, anniversary, childrenâs names, petâs names, favorite team, or childhood street are all discoverable through social media and public records. Never incorporate this information into passwords.
Mistake 4: Rotating Through Variations
When forced to change passwords, donât increment numbers or rotate through a set of favorites. âPassword1â becoming âPassword2â provides no security improvement. Generate completely new random passwords each time.
Mistake 5: Trusting Password Strength Meters
Many websites include password strength indicators, but these vary wildly in quality. Some mark âPassword1!â as strong because it meets complexity rules despite being trivially crackable. Use entropy calculation or trusted generators rather than these meters.
Generating Your Secure Passwords
Ready to put these principles into practice? Hereâs how to use our password generator:
- Set length to 16+ characters for important accounts, 12+ for lower-priority accounts
- Enable all character types: uppercase, lowercase, numbers, and symbols
- Generate and immediately copy to your password manager
- Generate fresh for each accountânever reuse generated passwords
- For memorable passwords, switch to passphrase mode and generate random word combinations
The generator uses cryptographic randomness from your browser, operates entirely client-side (nothing is transmitted or stored), and provides entropy information so you can verify strength.
Your Password Security Checklist
Implement these practices systematically:
Immediate actions:
- Install a reputable password manager if you donât have one
- Generate a strong, unique master password using the passphrase method
- Update passwords for email, banking, and other critical accounts using random generation
Ongoing practices:
- Generate unique random passwords for every new account
- Never type passwords manuallyâuse auto-fill to reduce phishing and typo risks
- Enable two-factor authentication wherever available
Periodic review:
- Check haveibeenpwned.com for breach notifications
- Update any passwords identified in breaches immediately
- Review password manager for duplicate or weak entries
Truly uncrackable passwords arenât a theoretical idealâtheyâre an achievable reality with the right tools and methods. By understanding how passwords are attacked and applying the principles of length, randomness, and uniqueness, you can effectively eliminate password-based vulnerabilities from your digital life.
Dr. Emily Rodriguez is a CISSP-certified cybersecurity researcher with a Ph.D. in Computer Science from MIT. She has published over 30 peer-reviewed papers on cryptography and password security.