BCRYPT_PBKDF(3) | Library Functions Manual | BCRYPT_PBKDF(3)

# NAME

`bcrypt_pbkdf` — bcrypt password-based key derivation function

# SYNOPSIS

System Utilities Library (libutil, -lutil)
`#include <util.h>`

int
`bcrypt_pbkdf`(const char *pass, size_t pass_len, const uint8_t *salt, size_t salt_len, uint8_t *key, size_t key_len, unsigned int rounds);

# DESCRIPTION

The `bcrypt_pbkdf` function converts a password into a byte array suitable for use as an encryption key. The password and salt values are combined and repeatedly hashed rounds times. The salt value should be randomly generated beforehand. The repeated hashing is designed to thwart discovery of the key via password guessing attacks. The higher the number of rounds, the slower each attempt will be.

# RETURN VALUES

The `bcrypt_pbkdf`() function returns 0 to indicate success and -1 for failure.

# SEE ALSO

bcrypt(3)

# STANDARDS

Niels Provos and David Mazieres, A Future-Adaptable Password Scheme, June 1999.

B. Kaliski, PKCS #5: Password-Based Cryptography Specification Version 2.0, RFC 2898, September 2000.

# CAVEATS

This implementation deviates slightly from the PBKDF2 standard by mixing output key bits nonlinearly. By mixing the output bytes together, an attacker is required to perform all of the work without taking any shortcuts.

June 6, 2025 | Debian