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libcanlock(3)		     libcanlock 3.3.2 manual		   libcanlock(3)

NAME
     cl_get_key - Create Cancel-Key with libcanlock

SYNOPSIS
     #include <libcanlock-3/canlock.h>

     char *cl_get_key(cl_hash_version hash,
		      const unsigned char *sec, size_t sec_len,
		      const unsigned char *msg, size_t msg_len);

     Supported values for hash (by version 3.0.0 of libcanlock):
     CL_SHA1 CL_SHA224 CL_SHA256 CL_SHA384 CL_SHA512

DESCRIPTION
     The  cl_get_key() function creates a <c-key> element according to the algo-
     rithm recommended by RFC 8315 in Section 4. The hash algorithm selected for
     <scheme> is used for the HMAC operation too.

     The hash algorithm for <scheme> is selected with hash.

     The local secret is specified with sec (sec_len must be set to  the  length
     of sec).
     The  length  of  the local secret should be at least the length of the hash
     that was selected for <scheme> (32 octets for SHA256).

     The Message-ID of the target article (the one that should be  cancelled  or
     superseded)  is  specified  with  msg (msg_len must be set to the length of
     msg).

     The Message-ID msg can be prepended with an optional User-ID. The length of
     the User-ID must be added to msg_len.  The User-ID must not  contain  angle
     brackets.

RETURN VALUE
     Upon  successful  completion  a  pointer  to the result string is returned.
     Otherwise, NULL is returned.

     On success the caller is responsible to call free()  for  the  pointer  re-
     turned as result.

AUTHORS
     Dennis Preiser
     (Based in part on the implementation from G. J. Andruk for Version 2)

     The  base64 implementation is written by Kungliga Tekniska Hogskolan (Royal
     Institute of Technology, Stockholm, Sweden)

     The hash algorithms are implemented with code from RFC 6234

REPORTING BUGS
     Report bugs to <mailto:michael.baeuerle@gmx.net>.

STANDARDS
     libcanlock tries to comply with the following standards:

     RFC 5537, RFC 6234, RFC 8315

SEE ALSO
     free(3),  cl_clear_secret(3),  cl_get_lock(3),  cl_split(3),  cl_verify(3),
     cl_verify_multi(3), canlock(1)

Unix				   2026-06-22			   libcanlock(3)
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