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DSA_generate_parameters.pod 3.0 KB

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  1. =pod
  2. =head1 NAME
  3. DSA_generate_parameters - generate DSA parameters
  4. =head1 SYNOPSIS
  5. #include <openssl/dsa.h>
  6. DSA *DSA_generate_parameters(int bits, unsigned char *seed,
  7. int seed_len, int *counter_ret, unsigned long *h_ret,
  8. void (*callback)(int, int, void *), void *cb_arg);
  9. =head1 DESCRIPTION
  10. DSA_generate_parameters() generates primes p and q and a generator g
  11. for use in the DSA.
  12. B<bits> is the length of the prime to be generated; the DSS allows a
  13. maximum of 1024 bits.
  14. If B<seed> is B<NULL> or B<seed_len> E<lt> 20, the primes will be
  15. generated at random. Otherwise, the seed is used to generate
  16. them. If the given seed does not yield a prime q, a new random
  17. seed is chosen and placed at B<seed>.
  18. DSA_generate_parameters() places the iteration count in
  19. *B<counter_ret> and a counter used for finding a generator in
  20. *B<h_ret>, unless these are B<NULL>.
  21. A callback function may be used to provide feedback about the progress
  22. of the key generation. If B<callback> is not B<NULL>, it will be
  23. called as follows:
  24. =over 4
  25. =item *
  26. When a candidate for q is generated, B<callback(0, m++, cb_arg)> is called
  27. (m is 0 for the first candidate).
  28. =item *
  29. When a candidate for q has passed a test by trial division,
  30. B<callback(1, -1, cb_arg)> is called.
  31. While a candidate for q is tested by Miller-Rabin primality tests,
  32. B<callback(1, i, cb_arg)> is called in the outer loop
  33. (once for each witness that confirms that the candidate may be prime);
  34. i is the loop counter (starting at 0).
  35. =item *
  36. When a prime q has been found, B<callback(2, 0, cb_arg)> and
  37. B<callback(3, 0, cb_arg)> are called.
  38. =item *
  39. Before a candidate for p (other than the first) is generated and tested,
  40. B<callback(0, counter, cb_arg)> is called.
  41. =item *
  42. When a candidate for p has passed the test by trial division,
  43. B<callback(1, -1, cb_arg)> is called.
  44. While it is tested by the Miller-Rabin primality test,
  45. B<callback(1, i, cb_arg)> is called in the outer loop
  46. (once for each witness that confirms that the candidate may be prime).
  47. i is the loop counter (starting at 0).
  48. =item *
  49. When p has been found, B<callback(2, 1, cb_arg)> is called.
  50. =item *
  51. When the generator has been found, B<callback(3, 1, cb_arg)> is called.
  52. =back
  53. =head1 RETURN VALUE
  54. DSA_generate_parameters() returns a pointer to the DSA structure, or
  55. B<NULL> if the parameter generation fails. The error codes can be
  56. obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
  57. =head1 BUGS
  58. Seed lengths E<gt> 20 are not supported.
  59. =head1 SEE ALSO
  60. L<dsa(3)|dsa(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>,
  61. L<DSA_free(3)|DSA_free(3)>
  62. =head1 HISTORY
  63. DSA_generate_parameters() appeared in SSLeay 0.8. The B<cb_arg>
  64. argument was added in SSLeay 0.9.0.
  65. In versions up to OpenSSL 0.9.4, B<callback(1, ...)> was called
  66. in the inner loop of the Miller-Rabin test whenever it reached the
  67. squaring step (the parameters to B<callback> did not reveal how many
  68. witnesses had been tested); since OpenSSL 0.9.5, B<callback(1, ...)>
  69. is called as in BN_is_prime(3), i.e. once for each witness.
  70. =cut