Pepper
What is Pepper?
PepperA server-side secret combined with each password before hashing, held separately from the database to mitigate offline cracking after a hash leak.
A pepper is a long, application-wide secret (typically 32 bytes or more) added to every password before it is processed by a hash function or KDF, in addition to the per-user salt. Unlike a salt, a pepper is stored outside the user-credentials database — for example in a configuration file, environment variable, or hardware security module — so that an attacker who only obtains the hash table cannot easily crack passwords offline. Implementations commonly use HMAC(pepper, password) before passing the result into Argon2id, or feed the pepper through a KDF as part of the secret material. Peppering is a defence-in-depth measure: it should never replace strong KDFs, salts, or rate limiting, but it raises the cost of database-only breaches.
● Examples
- 01
HMAC-SHA-256(pepper, password) computed in the application, then hashed with Argon2id.
- 02
Storing the pepper in an HSM so the application cannot exfiltrate it directly.
● Frequently asked questions
What is Pepper?
A server-side secret combined with each password before hashing, held separately from the database to mitigate offline cracking after a hash leak. It belongs to the Cryptography category of cybersecurity.
What does Pepper mean?
A server-side secret combined with each password before hashing, held separately from the database to mitigate offline cracking after a hash leak.
How do you defend against Pepper?
Defences for Pepper typically combine technical controls and operational practices, as detailed in the full definition above.
What are other names for Pepper?
Common alternative names include: Server-side key, Secret pepper.