1KCAPI_KDF_FB(3)              Programming Interface             KCAPI_KDF_FB(3)
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NAME

6       kcapi_kdf_fb - Feedback Mode Key Derivation Function
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SYNOPSIS

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

13       handle
14           [in] cipher handle allocated by caller. This cipher handle must be
15           allocated with kcapi_md_init. If the caller is interested in a KDF
16           using a keyed message digest, the caller should also call
17           kcapi_md_setkey before invoking this function.
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19       src
20           [in] Input data that should be transformed into a key (see below).
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22       slen
23           [in] Length of the src input data.
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25       dst
26           [out] Buffer to store the generated key in,
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28       dlen
29           [in] Length of the dst buffer. This value defines the number of
30           bytes generated by the KDF.
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DESCRIPTION

33       This function is an implementation of the KDF in feedback mode with a
34       non-NULL IV and with counter according to SP800-108 section 5.2. The IV
35       is supplied with src and must be equal to the digestsize of the used
36       cipher.
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38       In addition, the caller must provide Label || 0x00 || Context in src.
39       This src pointer must not be NULL as the IV is required. The ultimate
40       format of the src pointer is IV || Label || 0x00 || Context where the
41       length of the IV is equal to the block size (i.e. the digest size of
42       the underlying hash) of the PRF.
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44       return 0 upon success; a negative errno-style error code if an error
45       occurred
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AUTHOR

48       Stephan Mueller <smueller@chronox.de>
49           Author.
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52libkcapi Manual 1.4.0            January 2023                  KCAPI_KDF_FB(3)
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