Parameters/gcryctl to digest algorithms?

[Werner Koch]

On Sun, 23 Mar 2014 21:18, dbaryshkov at gmail.com said:

> digest calculation. I can add another algo for that s-box, however I fear
> that it would be an overkill. I was also thinking about reusing

Please use a new algorithm number.  In case you expect that you need
several of them in the uture, it is probably useful to reserve a range
of algorithm ids like:

GCRY_MD_GOSTR3411_94  = 308, /* GOST R 34.11-94.  */
GCRY_MD_STRIBOG256    = 309, /* GOST R 34.11-2012, 256 bit.  */
GCRY_MD_STRIBOG512    = 310  /* GOST R 34.11-2012, 512 bit.  */

GCRY_MD_GOSTR3411_XX  = 401  /* 402 to 4xx reserved for other variants. */

> flags part of md_open() call, but also couldn't come up with a good
> enough solution.

Flags require lots of special cases, ranges of algorithm ids can be
implemented in a generalized way:

  typedef struct gcry_md_spec
  {
    int algo;         /* Actually used algo.  */
+   int first_algo;   /* Modules supports algo range starting here ... */
+   int last_algo;    /* .. up to here.  */
    struct {
      unsigned int disabled:1;
      unsigned int fips:1;
    } flags;
    ...
  }
  
  static gcry_md_spec_t *
  spec_from_algo (int algo)
  {
    int idx;
    gcry_md_spec_t *spec;
  
    algo = map_algo (algo);
  
    for (idx = 0; (spec = digest_list[idx]); idx++)
-     if (algo == spec->algo)
+     if (algo >= spec->first_algo && algo <= spec->last_algo)
        return spec;
    return NULL;
  }
  

then it is up to the digest module to do whatever it needs to do.


Salam-Shalom,

   Werner

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