Diffie-Hellman functions(3)

NAME
Diffie-Hellman functions -

  Functions
const DH_METHOD * DH_imath_method (void)
const DH_METHOD * DH_ltm_method (void)
DH * DH_new (void)
DH * DH_new_method (ENGINE *engine)
void DH_free (DH *dh)
int DH_up_ref (DH *dh)
int DH_size (const DH *dh)
int DH_set_ex_data (DH *dh, int idx, void *data)
void * DH_get_ex_data (DH *dh, int idx)
int DH_generate_parameters_ex (DH *dh, int prime_len, int generator, BN_GENCB *cb)
int DH_check_pubkey (const DH *dh, const BIGNUM *pub_key, int *codes)
int DH_generate_key (DH *dh)
int DH_compute_key (unsigned char *shared_key, const BIGNUM *peer_pub_key, DH *dh)
int DH_set_method (DH *dh, const DH_METHOD *method)
const DH_METHOD * DH_null_method (void)
void DH_set_default_method (const DH_METHOD *meth)
const DH_METHOD * DH_get_default_method (void)

Detailed Description

See the DH - Diffie-Hellman key exchange for description and examples.

Function Documentation

  int DH_check_pubkey (const DH * dh, const BIGNUM * pub_key, int * codes)

Check that the public key is sane.

Parameters:
    dh the local peer DH parameters.
    pub_key the remote peer public key parameters.
    codes return that the failures of the pub_key are.

Returns:
    1 on success, 0 on failure and *codes is set the the combined fail check for the public key

Checks that the function performs are:

•   pub_key is not negative

•   pub_key > 1 and pub_key < p - 1, to avoid small subgroups attack.

•   if g == 2, pub_key have more then one bit set, if bits set is 1, log_2(pub_key) is trival

  int DH_compute_key (unsigned char * shared_key, const BIGNUM * peer_pub_key, DH * dh)

Complute the shared secret key.

Parameters:
    shared_key the resulting shared key, need to be at least DH_size() large.
    peer_pub_key the peer's public key.
    dh the dh key pair.

Returns:
    1 on success.

Checks that the pubkey passed in is valid using DH_check_pubkey().

  void DH_free (DH * dh)

Free a DH object and release related resources, like ENGINE, that the object was using.

Parameters:
    dh object to be freed.

  int DH_generate_key (DH * dh)

Generate a new DH private-public key pair. The dh parameter must be allocted first with DH_new(). dh->p and dp->g must be set.

Parameters:
    dh dh parameter.

Returns:
    1 on success.

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

Generate DH parameters for the DH object give parameters.

Parameters:
    dh The DH object to generate parameters for.
    prime_len length of the prime
    generator generator, g
    cb Callback parameters to show progress, can be NULL.

Returns:
    the maximum size in bytes of the out data.

  const DH_METHOD* DH_get_default_method (void)

Return the default DH implementation.

Returns:
    pointer to a DH_METHOD.

  void* DH_get_ex_data (DH * dh, int idx)

Get the data for index idx in the DH object.

Parameters:
    dh DH object.
    idx index to get the data for.

Returns:
    the object store in index idx

  const DH_METHOD* DH_imath_method (void)

DH implementation using libimath.

Returns:
    the DH_METHOD for the DH implementation using libimath.

  const DH_METHOD* DH_ltm_method (void)

DH implementation using libimath.

Returns:
    the DH_METHOD for the DH implementation using libimath.

  DH* DH_new (void)

Create a new DH object using DH_new_method(NULL), see DH_new_method().

Returns:
    a newly allocated DH object.

  DH* DH_new_method (ENGINE * engine)

Create a new DH object from the given engine, if the NULL is used, the default engine is used. Free the DH object with DH_free().

Parameters:
    engine The engine to use to allocate the DH object.

Returns:
    a newly allocated DH object.

  const DH_METHOD* DH_null_method (void)

Return the dummy DH implementation.

Returns:
    pointer to a DH_METHOD.

  void DH_set_default_method (const DH_METHOD * meth)

Set the default DH implementation.

Parameters:
    meth pointer to a DH_METHOD.

  int DH_set_ex_data (DH * dh, int idx, void * data)

Set the data index idx in the DH object to data.

Parameters:
    dh DH object.
    idx index to set the data for.
    data data to store for the index idx.

Returns:
    1 on success.

  int DH_set_method (DH * dh, const DH_METHOD * method)

Set a new method for the DH keypair.

Parameters:
    dh dh parameter.
    method the new method for the DH parameter.

Returns:
    1 on success.

  int DH_size (const DH * dh)

The maximum output size of the DH_compute_key() function.

Parameters:
    dh The DH object to get the size from.

Returns:
    the maximum size in bytes of the out data.

  int DH_up_ref (DH * dh)

Add a reference to the DH object. The object should be free with DH_free() to drop the reference.

Parameters:
    dh the object to increase the reference count too.

Returns:
    the updated reference count, can't safely be used except for debug printing.