libressl-DH_generate_parameters3
Generate and check diffie-hellman parameters
Usage
Crypto Library
(libcrypto,
-lcrypto)
int
int
int
Deprecated:
DH *
Overview
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.
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_GENCB_call(3).
DH_check() validates Diffie-Hellman parameters. If no problems are found, *codes is set to zero. Otherwise, one or more of the following bits are set:
- DH_CHECK_P_NOT_PRIME
-
The parameter dh->p is not prime.
- DH_CHECK_P_NOT_SAFE_PRIME
-
The parameter dh->p is not a safe prime.
- DH_UNABLE_TO_CHECK_GENERATOR
-
The generator dh->g cannot be checked for suitability: it is neither 2 nor 5.
- DH_NOT_SUITABLE_GENERATOR
-
The generator dh->g is not suitable.
DH_check_pub_key() checks whether pub_key is a valid public key when using the domain parameters contained in dh. If no problems are found, *codes is set to zero. Otherwise, one or more of the following bits are set:
- DH_CHECK_PUBKEY_TOO_SMALL
-
pub_key is less than or equal to 1.
- DH_CHECK_PUBKEY_TOO_LARGE
-
pub_key is greater than or equal to dh->p - 1.
- DH_CHECK_PUBKEY_INVALID
-
dh->q is set but pub_key to the power of dh->q is not 1 modulo dh->p.
Return values
DH_generate_parameters_ex(), DH_check(), and DH_check_pub_key() return 1 if the check could be performed or 0 otherwise.
DH_generate_parameters() (deprecated) returns a pointer to the DH structure, or NULL if the parameter generation fails.
The error codes can be obtained by ERR_get_error(3).
Caveats
DH_generate_parameters_ex() and DH_generate_parameters() may run for several hours before finding a suitable prime.
The parameters generated by DH_generate_parameters_ex() and DH_generate_parameters() are not to be used in signature schemes.