Ubuntu Manpage: DH_generate_parameters_ex, DH_generate_parameters, DH_check, DH_check_params, DH_check

Provided by: libssl-doc_3.0.13-0ubuntu3.4_all

NAME

       DH_generate_parameters_ex, DH_generate_parameters, DH_check, DH_check_params, DH_check_ex,
       DH_check_params_ex, DH_check_pub_key_ex - generate and check Diffie-Hellman parameters

SYNOPSIS

        #include <openssl/dh.h>

       The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely
       by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

        int DH_generate_parameters_ex(DH *dh, int prime_len, int generator, BN_GENCB *cb);

        int DH_check(DH *dh, int *codes);
        int DH_check_params(DH *dh, int *codes);

        int DH_check_ex(const DH *dh);
        int DH_check_params_ex(const DH *dh);
        int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key);

       The following functions have been deprecated since OpenSSL 0.9.8, and can be hidden
       entirely by defining OPENSSL_API_COMPAT with a suitable version value, see
       openssl_user_macros(7):

        DH *DH_generate_parameters(int prime_len, int generator,
                                   void (*callback)(int, int, void *), void *cb_arg);

DESCRIPTION

All of the functions described on this page are deprecated. Applications should instead
use EVP_PKEY_check(3), EVP_PKEY_public_check(3), EVP_PKEY_private_check(3) and
EVP_PKEY_param_check(3).

DH_generate_parameters_ex() generates Diffie-Hellman parameters that can be shared among a
group of users, and stores them in the provided DH structure. The pseudo-random number
generator must be seeded before calling it. The parameters generated by
DH_generate_parameters_ex() should not be used in signature schemes.

prime_len is the length in bits of the safe prime to be generated. generator is a small
number > 1, typically 2 or 5.

A callback function may be used to provide feedback about the progress of the key
generation. If cb is not NULL, it will be called as described in BN_generate_prime(3)
while a random prime number is generated, and when a prime has been found,
BN_GENCB_call(cb, 3, 0) is called. See BN_generate_prime_ex(3) for information on the
BN_GENCB_call() function.

DH_generate_parameters() is similar to DH_generate_prime_ex() but expects an old-style
callback function; see BN_generate_prime(3) for information on the old-style callback.

DH_check_params() confirms that the p and g are likely enough to be valid. This is a
lightweight check, if a more thorough check is needed, use DH_check(). The value of
*codes is updated with any problems found. If *codes is zero then no problems were found,
otherwise the following bits may be set:

DH_CHECK_P_NOT_PRIME
The parameter p has been determined to not being an odd prime. Note that the lack of
this bit doesn't guarantee that p is a prime.

DH_NOT_SUITABLE_GENERATOR
The generator g is not suitable. Note that the lack of this bit doesn't guarantee
that g is suitable, unless p is known to be a strong prime.

DH_MODULUS_TOO_SMALL
The modulus is too small.

DH_MODULUS_TOO_LARGE
The modulus is too large.

DH_check() confirms that the Diffie-Hellman parameters dh are valid. The value of *codes
is updated with any problems found. If *codes is zero then no problems were found,
otherwise the following bits may be set:

DH_CHECK_P_NOT_PRIME
The parameter p is not prime.

DH_CHECK_P_NOT_SAFE_PRIME
The parameter p is not a safe prime and no q value is present.

DH_UNABLE_TO_CHECK_GENERATOR
The generator g cannot be checked for suitability.

DH_NOT_SUITABLE_GENERATOR
The generator g is not suitable.

DH_CHECK_Q_NOT_PRIME
The parameter q is not prime.

DH_CHECK_INVALID_Q_VALUE
The parameter q is invalid.

DH_CHECK_INVALID_J_VALUE
The parameter j is invalid.

If 0 is returned or *codes is set to a nonzero value the supplied parameters should not be
used for Diffie-Hellman operations otherwise the security properties of the key exchange
are not guaranteed.

DH_check_ex(), DH_check_params() and DH_check_pub_key_ex() are similar to DH_check() and
DH_check_params() respectively, but the error reasons are added to the thread's error
queue instead of provided as return values from the function.

RETURN VALUES

       DH_generate_parameters_ex(), DH_check() and DH_check_params() return 1 if the check could
       be performed, 0 otherwise.

       DH_generate_parameters() returns a pointer to the DH structure or NULL if the parameter
       generation fails.

       DH_check_ex(), DH_check_params() and DH_check_pub_key_ex() return 1 if the check is
       successful, 0 for failed.

       The error codes can be obtained by ERR_get_error(3).

HISTORY

       All of these functions were deprecated in OpenSSL 3.0.

       DH_generate_parameters() was deprecated in OpenSSL 0.9.8; use DH_generate_parameters_ex()
       instead.

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