NAME

       kcapi_kdf_fb - Feedback Mode Key Derivation Function

SYNOPSIS

       ssize_t kcapi_kdf_fb(struct kcapi_handle * handle, const uint8_t * src, size_t slen, uint8_t * dst,
                            size_t dlen);

ARGUMENTS

       handle
           [in] cipher handle allocated by caller. This cipher handle must be allocated with kcapi_md_init. If
           the caller is interested in a KDF using a keyed message digest, the caller should also call
           kcapi_md_setkey before invoking this function.

       src
           [in] Input data that should be transformed into a key (see below).

       slen
           [in] Length of the src input data.

       dst
           [out] Buffer to store the generated key in,

       dlen
           [in] Length of the dst buffer. This value defines the number of bytes generated by the KDF.

DESCRIPTION

       This function is an implementation of the KDF in feedback mode with a non-NULL IV and with counter
       according to SP800-108 section 5.2. The IV is supplied with src and must be equal to the digestsize of
       the used cipher.

       In addition, the caller must provide Label || 0x00 || Context in src. This src pointer must not be NULL
       as the IV is required. The ultimate format of the src pointer is IV || Label || 0x00 || Context where the
       length of the IV is equal to the block size (i.e. the digest size of the underlying hash) of the PRF.

       return 0 upon success; a negative errno-style error code if an error occurred

AUTHOR

       Stephan Mueller <smueller@chronox.de>
           Author.

COPYRIGHT

libkcapi Manual 1.5.0                              April 2024                                    KCAPI_KDF_FB(3)