=pod

=head1 NAME

EVP_KDF-PBKDF2 - The PBKDF2 EVP_KDF implementation

=head1 DESCRIPTION

Support for computing the B<PBKDF2> password-based KDF through the B<EVP_KDF>
API.

The EVP_KDF-PBKDF2 algorithm implements the PBKDF2 password-based key
derivation function, as described in SP800-132; it derives a key from a password
using a salt and iteration count.

The output is considered to be a cryptographic key.

=head2 Identity

"PBKDF2" is the name for this implementation; it
can be used with the EVP_KDF_fetch() function.

=head2 Supported parameters

The supported parameters are:

=over 4

=item "pass" (B<OSSL_KDF_PARAM_PASSWORD>) <octet string>

=item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>

=item "iter" (B<OSSL_KDF_PARAM_ITER>) <unsigned integer>

This parameter has a default value of 2048.

=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>

=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>

These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.

B<Note:> PBKDF2 uses HMAC internally, which does not support eXtendable Output
Function (XOF) digests such as SHAKE128 or SHAKE256. Attempting to use an XOF
digest with PBKDF2 will result in an error.

=item "pkcs5" (B<OSSL_KDF_PARAM_PKCS5>) <integer>

This parameter can be used to enable or disable SP800-132 compliance checks.
Setting the mode to 0 enables the compliance checks.

The checks performed are:

=over 4

=item - the iteration count is at least 1000.

=item - the salt length is at least 128 bits.

=item - the derived key length is at least 112 bits.

=item - the password length is at least minimum length.

The default minimum password length can be configured when OpenSSL is
compiled by setting B<-DKDF_PBKDF2_MIN_PASSWORD_LEN=length>. If not
set then 1 is used for the default provider and 8 for the FIPS
provider since 4.0.0. Please consult the security policy document of
your FIPS provider from your vendor for further details, as
implementation often vary by each vendor.

=back

The default provider uses a default mode of 1 for backwards compatibility,
and the FIPS provider uses a default mode of 0.
This option breaks FIPS compliance if it causes the approved "fips-indicator"
to return 0.

=item "fips-indicator" (B<OSSL_KDF_PARAM_FIPS_APPROVED_INDICATOR>) <integer>

This option is used by the OpenSSL FIPS provider.

A getter that returns 1 if the operation is FIPS approved, or 0
otherwise.  This may be used after calling EVP_KDF_derive. It returns
0 if "pkcs5" is set to 1 and the password length, derived key length,
salt length or iteration count test fails.

=back

=head1 NOTES

A typical application of this algorithm is to derive keying material for an
encryption algorithm from a password in the "pass", a salt in "salt",
and an iteration count.

Increasing the "iter" parameter slows down the algorithm which makes it
harder for an attacker to perform a brute force attack using a large number
of candidate passwords.

No assumption is made regarding the given password; it is simply treated as a
byte sequence.

=head1 CONFORMING TO

SP800-132

=head1 SEE ALSO

L<EVP_KDF(3)>,
L<EVP_KDF_CTX_new(3)>,
L<EVP_KDF_CTX_free(3)>,
L<EVP_KDF_CTX_set_params(3)>,
L<EVP_KDF_derive(3)>,
L<EVP_KDF(3)/PARAMETERS>

=head1 HISTORY

This functionality was added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2018-2026 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

=cut
