NAME

       shishi_decrypt_ivupdate - API function

SYNOPSIS

       #include <shishi.h>

       int  shishi_decrypt_ivupdate(Shishi * handle, Shishi_key * key, int keyusage, const char *
       iv, size_t ivlen, char ** ivout, size_t * ivoutlen, const char * in, size_t inlen, char **
       out, size_t * outlen);

ARGUMENTS

       Shishi * handle
                   shishi handle as allocated by shishi_init().

       Shishi_key * key
                   key to decrypt with.

       int keyusage
                   integer specifying what this key is decrypting.

       const char * iv
                   input array with initialization vector

       size_t ivlen
                   size of input array with initialization vector.

       char ** ivout
                   output array with newly allocated updated initialization vector.

       size_t * ivoutlen
                   size of output array with updated initialization vector.

       const char * in
                   input array with data to decrypt.

       size_t inlen
                   size of input array with data to decrypt.

       char ** out output array with newly allocated decrypted data.

       size_t * outlen
                   output variable with size of newly allocated output array.

DESCRIPTION

       Decrypts  data  using  specified  initialization vector and key.  The key actually used is
       derived using the key usage.  If key usage is 0, no  key  derivation  is  used.   The  OUT
       buffer must be deallocated by the caller.  If IVOUT or IVOUTLEN is NULL, the updated IV is
       not saved anywhere.

       Note that DECRYPT(ENCRYPT(data)) does not necessarily yield data exactly.  Some encryption
       types  add  pad  to  make  the  data  fit into the block size of the encryption algorithm.
       Furthermore, the pad is not guaranteed to look  in  any  special  way,  although  existing
       implementations  often  pad  with  the zero byte.  This means that you may have to "frame"
       data, so it is possible to infer the original length after decryption.  Compare ASN.1  DER
       which contains such information.

RETURN VALUE

       Returns SHISHI_OK iff successful.

REPORTING BUGS

       Report      bugs      to      <bug-shishi@gnu.org>.      GNU     Shishi     home     page:
       http://www.gnu.org/software/shishi/     General     help     using      GNU      software:
       http://www.gnu.org/gethelp/

COPYRIGHT

       Copyright © 2002-2022 Simon Josefsson.
       Copying  and distribution of this file, with or without modification, are permitted in any
       medium without royalty provided the copyright notice and this notice are preserved.

SEE ALSO

       The full documentation for shishi is maintained as a Texinfo  manual.   If  the  info  and
       shishi programs are properly installed at your site, the command

              info shishi

       should give you access to the complete manual.