Guides
How passwords, passphrases and the alternatives actually work: what makes a secret strong, how attacks proceed, and what the standards say. Each guide cites its sources.
Making strong secrets
Passphrases, entropy, length and PINs: how a secret gets its strength.
Making strong secretsHow passphrases workA passphrase is several words chosen at random from a known list. Its strength comes from the size of the list and the number of words, not from the words being secret.5 min read
Making strong secretsPassword entropy, explained in bitsEntropy counts how many equally likely secrets a method could have produced, in powers of two. It is exact for random generators and only a rough guess for anything a person picked.4 min read
Making strong secretsWhy length beats complexityEach added character multiplies the search space; each added character class only widens it a little. NIST's 2025 guidance sets a 15-character minimum and bans composition rules.4 min read
Making strong secretsHow many words should a passphrase have?It depends on whether an attacker can guess offline. Four random words resist online guessing; five or six are the usual floor for secrets that might face an offline attack.5 min read
Making strong secretsMaking a passphrase with real diceRoll five dice, read them left to right, look up the five-digit number in the EFF large wordlist, and repeat for each word. No computer has to be trusted with the choice.5 min read
Making strong secretsRandom vs human-chosen passwordsRandom passwords have a strength you can calculate. Human-chosen ones cluster around words, names, dates and patterns, so attackers try those first and the real strength is far lower than the length suggests.5 min read
Making strong secretsPassword rules that backfireMany familiar password rules make passwords more predictable or push people toward unsafe habits. NIST SP 800-63B-4 now forbids several of them outright.4 min read
Making strong secretsShould you change passwords regularly?Changing a password on a timer rarely stops an attacker and tends to produce predictable passwords. NIST now forbids scheduled changes but requires a change when there is evidence of compromise.5 min read
Making strong secretsPINs explained: why four digits can be enoughA PIN has very few possibilities, so its safety comes from the device or service refusing to let anyone guess more than a handful of times. Without that limit, any PIN falls almost instantly.5 min read
Making strong secretsChoosing a master passwordThe master password guards every other password, and a copied vault can be attacked offline with no lockout. A random passphrase of six or more words gives a wide margin and is practical to memorize.5 min read
How passwords are attacked
Breaches, hashing, guessing and the patterns attackers try first.
How passwords are attackedHow data breaches expose passwordsA leaked database is not automatically a list of passwords. How the site stored them decides how much work an attacker faces.5 min read
How passwords are attackedPassword hashing explained: salts and cost factorsPassword hashing turns a password into a stored value that is cheap to check once and expensive to check billions of times. Salts and cost factors are how.5 min read
How passwords are attackedHow long does it take to crack a password?A crack time is just the size of the search divided by the guess rate. The hard parts are knowing the rate and knowing the real size of the search.5 min read
How passwords are attackedWhat makes a password common?Common passwords are the ones attackers try first. Here is what they look like, measured from a real 10,000-entry list.4 min read
How passwords are attackedCredential stuffing and password reuseCredential stuffing needs no guessing at all: it replays a known email and password on other sites. Reuse is what makes it work.5 min read
How passwords are attackedKeyboard patterns and letter substitutionsKeyboard walks and letter-for-symbol swaps look complex but are among the first things guessing tools try. Here is how little they add, counted.5 min read
How passwords are attackedChecking breached passwords with k-anonymityA documented way to ask 'has this password been in a breach?' without revealing it, and why this site still chooses not to ask.5 min read
How passwords are attackedPhishing and passwords: why strength doesn't helpPhishing does not guess passwords; it asks for them. Strength is irrelevant to it, which is why defenses focus on where the password is entered.4 min read
How passwords are attackedHow password strength meters workA strength meter guesses how an attacker would guess. Different meters model the attacker differently, which is why they disagree.5 min read
How passwords are attackedWi-Fi passwords: how WPA2 and WPA3 use themA Wi-Fi passphrase faces a different attack from a website password: under WPA2 it can be guessed offline, with no login limit.5 min read
Beyond the password
Password managers, two-factor authentication, passkeys and recovery.
Beyond the passwordHow password managers workA vendor-neutral look inside password managers: the encrypted vault, the master password, autofill by domain, sync, and what can still go wrong.6 min read
Beyond the passwordTwo-factor authentication explainedThe factors, the common second-factor methods side by side, and why a code you type can be relayed by a phishing page while a security key cannot.5 min read
Beyond the passwordHow authenticator apps make 6-digit codesStep by step through TOTP (RFC 6238) and HOTP (RFC 4226): the shared secret, the 30-second counter, the HMAC, the truncation, and an official test vector.5 min read
Beyond the passwordPasskeys explained: public keys instead of passwordsWhat a passkey actually is, how a login works step by step, why a look-alike site gets nothing, and what NIST says about passkeys that sync.5 min read
Beyond the passwordRecovery codes and backups: how they workRecovery codes are one-time secrets for when your usual login fails. Here is how they are generated, how strong they need to be, and where they fit.5 min read
Beyond the passwordSecurity questions: why NIST says noSecurity questions ask for facts that are often public or easy to guess. Here is the evidence, the NIST rule, and what treating the answer as a password does.4 min read
Under the hood
How a trustworthy generator picks characters, and the details that matter.
Under the hoodHow password generators workInside a password generator: why it must use the browser's CSPRNG and not Math.random, how it picks characters fairly, and how settings turn into bits.5 min read
Under the hoodModulo bias and rejection sampling, worked throughA small arithmetic trap in password generators, worked through with real numbers: where the bias comes from, how big it is, and how to remove it.5 min read
Under the hoodCharacter sets, look-alikes and Unicode in passwordsThe character sets behind password strength figures, the real cost of leaving out confusable characters, and why accented letters can break a login.5 min read
Under the hoodPassword length limits: minimums, maximums, truncationLength limits explained: the NIST minimums, why a maximum of at least 64 is expected, the bcrypt 72-byte edge, and the math of a truncated password.5 min read
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