Diffie-Hellman functions

Functions
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)

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Detailed Description

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

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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_ltm_method

(

void

)

DH implementation using libtommath.

Returns:

the DH_METHOD for the DH implementation using libtommath.

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.