Passphrase vs Password: Which Is More Secure?

A password is typically a string of mixed characters. A passphrase is multiple words strung together. Both can be equally secure — but passphrases have advantages for cases where you need to memorize the secret.

What is a passphrase?

A passphrase is two or more random words:

correct horse battery staple
marble engine sunset radio
purple volcano coffee lamp

The key word is random. Phrases that come from your head — “ilovemy dog” or “letmein2026” — aren’t secure. Random word passphrases selected from a large wordlist are.

Entropy comparison

Security is measured in bits of entropy — how many guesses an attacker needs to brute-force the password.

Random character password (full ASCII charset, 95 options per character):

• 12 characters: ~79 bits
• 16 characters: ~105 bits
• 20 characters: ~131 bits

Random passphrase (Diceware, 7,776 words per roll):

• 4 words: ~51 bits
• 5 words: ~64 bits
• 6 words: ~77 bits
• 7 words: ~90 bits
• 8 words: ~103 bits

A 6-word Diceware passphrase (~77 bits) is roughly equivalent to a 12-character random character password in entropy. A 7-word passphrase (~90 bits) is very strong for most purposes.

When to use a passphrase

Use a passphrase when you need to memorize the secret:

• Password manager master password
• Full-disk encryption password (VeraCrypt, LUKS)
• PGP key passphrase
• SSH key passphrase
• Shared team secrets passed verbally

Use a random character password (via password manager) for everything else:

• Online account logins
• API keys
• Database passwords

The advantage of passphrases is memorability — four random words are much easier to remember than Xk9#mQ2!pLr7vN. The advantage of random character passwords is compactness — they pack more entropy per character.

How Diceware works

Diceware uses physical dice to ensure randomness:

1. Roll 5 dice and record the numbers (e.g., 3-4-2-1-6)
2. Look up the number in the Diceware wordlist (34216 = “mouse”)
3. Repeat for each word

34216 = mouse
16326 = candy
52421 = pine
21341 = dry
46643 = rock
55624 = smart

Result: mouse candy pine dry rock smart

You can also use an offline Diceware tool or a password manager’s passphrase generator. The key is that the words are selected randomly, not by you.

Diceware wordlist size

The standard Diceware list has 7,776 words (6^5, since each word is chosen with 5 dice rolls). Each word contributes log₂(7776) ≈ 12.9 bits of entropy.

Some generators use larger word lists (EFF word lists have 7,776 words carefully chosen to be unambiguous when spoken). The entropy per word varies with list size.

The human-phrase trap

The biggest mistake is using a memorable sentence or phrase that comes from your head:

# These look like passphrases but are weak:
ilovemydog
correcthorsebatterystaple  ← famous xkcd example; now in attack wordlists
letmein1234
myfavoritecolor

Phrases from culture, movies, books, or your personal life are in attack wordlists. Only random selection from a large wordlist provides the security that passphrases promise.

NIST stance on passphrases

NIST SP 800-63B recommends allowing long passwords (passphrases) and not penalizing length. Verifiers should:

• Accept up to 64+ characters (enabling passphrases)
• Not restrict special characters or spaces
• Not force arbitrary complexity rules that make passphrases harder

Practical recommendation

Use case	Recommendation
Password manager master password	6-word Diceware passphrase
Full-disk encryption	6-7 word Diceware passphrase
PGP/SSH key	6-word Diceware passphrase
Website accounts	20-char random password (via manager)
API keys	32+ char random string (base62 or hex)
Shared team credentials	Password manager’s sharing feature

For accounts where you have a password manager, use the longest random password the site allows. For secrets you must memorize, use a random passphrase.

Generate strong passwords and passphrases at passwordgen.io.