NAME

       kcapi_kdf_fb - Feedback Mode Key Derivation Function

SYNOPSIS

       int32_t kcapi_kdf_fb(struct kcapi_handle * handle, const uint8_t * src, uint32_t slen,
                            uint8_t * dst, uint32_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.

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