This file contains ECDH definitions and functions. More...

#include "mbedtls/private_access.h"
#include "mbedtls/build_info.h"
#include "mbedtls/ecp.h"

Include dependency graph for ecdh.h:

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Data Structures
struct	mbedtls_ecdh_context
	The ECDH context structure. More...

Macros
#define	MBEDTLS_ECDH_LEGACY_CONTEXT

Typedefs
typedef struct mbedtls_ecdh_context	mbedtls_ecdh_context
	The ECDH context structure. More...

Enumerations
enum	mbedtls_ecdh_side { MBEDTLS_ECDH_OURS, MBEDTLS_ECDH_THEIRS }

Functions
int	mbedtls_ecdh_can_do (mbedtls_ecp_group_id gid)
	Check whether a given group can be used for ECDH. More...

int	mbedtls_ecdh_gen_public (mbedtls_ecp_group grp, mbedtls_mpi d, mbedtls_ecp_point Q, int(f_rng)(void , unsigned char , size_t), void *p_rng)
	This function generates an ECDH keypair on an elliptic curve. More...

int	mbedtls_ecdh_compute_shared (mbedtls_ecp_group grp, mbedtls_mpi z, const mbedtls_ecp_point Q, const mbedtls_mpi d, int(f_rng)(void , unsigned char , size_t), void p_rng)
	This function computes the shared secret. More...

void	mbedtls_ecdh_init (mbedtls_ecdh_context *ctx)
	This function initializes an ECDH context. More...

int	mbedtls_ecdh_setup (mbedtls_ecdh_context *ctx, mbedtls_ecp_group_id grp_id)
	This function sets up the ECDH context with the information given. More...

void	mbedtls_ecdh_free (mbedtls_ecdh_context *ctx)
	This function frees a context. More...

int	mbedtls_ecdh_make_params (mbedtls_ecdh_context ctx, size_t olen, unsigned char buf, size_t blen, int(f_rng)(void , unsigned char , size_t), void *p_rng)
	This function generates an EC key pair and exports its in the format used in a TLS ServerKeyExchange handshake message. More...

int	mbedtls_ecdh_read_params (mbedtls_ecdh_context ctx, const unsigned char buf, const unsigned char end)
	This function parses the ECDHE parameters in a TLS ServerKeyExchange handshake message. More...

int	mbedtls_ecdh_get_params (mbedtls_ecdh_context ctx, const mbedtls_ecp_keypair key, mbedtls_ecdh_side side)
	This function sets up an ECDH context from an EC key. More...

int	mbedtls_ecdh_make_public (mbedtls_ecdh_context ctx, size_t olen, unsigned char buf, size_t blen, int(f_rng)(void , unsigned char , size_t), void *p_rng)
	This function generates a public key and exports it as a TLS ClientKeyExchange payload. More...

int	mbedtls_ecdh_read_public (mbedtls_ecdh_context ctx, const unsigned char buf, size_t blen)
	This function parses and processes the ECDHE payload of a TLS ClientKeyExchange message. More...

int	mbedtls_ecdh_calc_secret (mbedtls_ecdh_context ctx, size_t olen, unsigned char buf, size_t blen, int(f_rng)(void , unsigned char , size_t), void *p_rng)
	This function derives and exports the shared secret. More...

void	mbedtls_ecdh_enable_restart (mbedtls_ecdh_context *ctx)
	This function enables restartable EC computations for this context. (Default: disabled.) More...

Detailed Description

This file contains ECDH definitions and functions.

The Elliptic Curve Diffie-Hellman (ECDH) protocol is an anonymous key agreement protocol allowing two parties to establish a shared secret over an insecure channel. Each party must have an elliptic-curve public–private key pair.

For more information, see NIST SP 800-56A Rev. 2: Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography.

Definition in file ecdh.h.

Macro Definition Documentation

#define MBEDTLS_ECDH_LEGACY_CONTEXT

Definition at line 54 of file ecdh.h.

Typedef Documentation

typedef struct mbedtls_ecdh_context mbedtls_ecdh_context

The ECDH context structure.

Warning: Performing multiple operations concurrently on the same ECDSA context is not supported; objects of this type should not be shared between multiple threads.

Enumeration Type Documentation

enum mbedtls_ecdh_side

Defines the source of the imported EC key.

Enumerator
MBEDTLS_ECDH_OURS	Our key.
MBEDTLS_ECDH_THEIRS	The key of the peer.

Definition at line 71 of file ecdh.h.

Function Documentation

int mbedtls_ecdh_calc_secret	(	mbedtls_ecdh_context *	ctx,
		size_t *	olen,
		unsigned char *	buf,
		size_t	blen,
		int()(void , unsigned char *, size_t)	f_rng,
		void *	p_rng
	)

This function derives and exports the shared secret.

This is the last function used by both TLS client and servers.

Note: If f_rng is not NULL, it is used to implement countermeasures against side-channel attacks. For more information, see mbedtls_ecp_mul().

See Also: ecp.h

Parameters

ctx	The ECDH context to use. This must be initialized and have its own private key generated and the peer's public key imported.
olen	The address at which to store the total number of Bytes written on success. This must not be `NULL`.
buf	The buffer to write the generated shared key to. This must be a writable buffer of size `blen` Bytes.
blen	The length of the destination buffer `buf` in Bytes.
f_rng	The RNG function to use. This must not be `NULL`.
p_rng	The RNG context. This may be `NULL` if `f_rng` doesn't need a context argument.

Returns: 0 on success.; MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of operations was reached: see mbedtls_ecp_set_max_ops().; Another MBEDTLS_ERR_ECP_XXX error code on failure.

int mbedtls_ecdh_can_do ( mbedtls_ecp_group_id gid )

Check whether a given group can be used for ECDH.

Parameters

gid	The ECP group ID to check.

Returns: 1 if the group can be used, 0 otherwise

int mbedtls_ecdh_compute_shared	(	mbedtls_ecp_group *	grp,
		mbedtls_mpi *	z,
		const mbedtls_ecp_point *	Q,
		const mbedtls_mpi *	d,
		int()(void , unsigned char *, size_t)	f_rng,
		void *	p_rng
	)

This function computes the shared secret.

This function performs the second of two core computations implemented during the ECDH key exchange. The first core computation is performed by mbedtls_ecdh_gen_public().

See Also: ecp.h

Note: If f_rng is not NULL, it is used to implement countermeasures against side-channel attacks. For more information, see mbedtls_ecp_mul().

Parameters

grp	The ECP group to use. This must be initialized and have domain parameters loaded, for example through mbedtls_ecp_load() or mbedtls_ecp_tls_read_group().
z	The destination MPI (shared secret). This must be initialized.
Q	The public key from another party. This must be initialized.
d	Our secret exponent (private key). This must be initialized.
f_rng	The RNG function to use. This must not be `NULL`.
p_rng	The RNG context to be passed to `f_rng`. This may be `NULL` if `f_rng` is `NULL` or doesn't need a context argument.

Returns: 0 on success.; Another MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code on failure.

void mbedtls_ecdh_enable_restart ( mbedtls_ecdh_context * ctx )

This function enables restartable EC computations for this context. (Default: disabled.)

See Also: mbedtls_ecp_set_max_ops()

Note: It is not possible to safely disable restartable computations once enabled, except by free-ing the context, which cancels possible in-progress operations.

Parameters

ctx	The ECDH context to use. This must be initialized.

void mbedtls_ecdh_free ( mbedtls_ecdh_context * ctx )

This function frees a context.

Parameters

ctx	The context to free. This may be `NULL`, in which case this function does nothing. If it is not `NULL`, it must point to an initialized ECDH context.

int mbedtls_ecdh_gen_public	(	mbedtls_ecp_group *	grp,
		mbedtls_mpi *	d,
		mbedtls_ecp_point *	Q,
		int()(void , unsigned char *, size_t)	f_rng,
		void *	p_rng
	)

This function generates an ECDH keypair on an elliptic curve.

This function performs the first of two core computations implemented during the ECDH key exchange. The second core computation is performed by mbedtls_ecdh_compute_shared().

See Also: ecp.h

Parameters

grp	The ECP group to use. This must be initialized and have domain parameters loaded, for example through mbedtls_ecp_load() or mbedtls_ecp_tls_read_group().
d	The destination MPI (private key). This must be initialized.
Q	The destination point (public key). This must be initialized.
f_rng	The RNG function to use. This must not be `NULL`.
p_rng	The RNG context to be passed to `f_rng`. This may be `NULL` in case `f_rng` doesn't need a context argument.

Returns: 0 on success.; Another MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code on failure.

int mbedtls_ecdh_get_params	(	mbedtls_ecdh_context *	ctx,
		const mbedtls_ecp_keypair *	key,
		mbedtls_ecdh_side	side
	)

This function sets up an ECDH context from an EC key.

It is used by clients and servers in place of the ServerKeyEchange for static ECDH, and imports ECDH parameters from the EC key information of a certificate.

See Also: ecp.h

Parameters

ctx	The ECDH context to set up. This must be initialized.
key	The EC key to use. This must be initialized.
side	Defines the source of the key. Possible values are: MBEDTLS_ECDH_OURS: The key is ours. MBEDTLS_ECDH_THEIRS: The key is that of the peer.

Returns: 0 on success.; Another MBEDTLS_ERR_ECP_XXX error code on failure.

void mbedtls_ecdh_init ( mbedtls_ecdh_context * ctx )

This function initializes an ECDH context.

Parameters

ctx	The ECDH context to initialize. This must not be `NULL`.

int mbedtls_ecdh_make_params	(	mbedtls_ecdh_context *	ctx,
		size_t *	olen,
		unsigned char *	buf,
		size_t	blen,
		int()(void , unsigned char *, size_t)	f_rng,
		void *	p_rng
	)

This function generates an EC key pair and exports its in the format used in a TLS ServerKeyExchange handshake message.

This is the second function used by a TLS server for ECDHE ciphersuites. (It is called after mbedtls_ecdh_setup().)

See Also: ecp.h

Parameters

ctx	The ECDH context to use. This must be initialized and bound to a group, for example via mbedtls_ecdh_setup().
olen	The address at which to store the number of Bytes written.
buf	The destination buffer. This must be a writable buffer of length `blen` Bytes.
blen	The length of the destination buffer `buf` in Bytes.
f_rng	The RNG function to use. This must not be `NULL`.
p_rng	The RNG context to be passed to `f_rng`. This may be `NULL` in case `f_rng` doesn't need a context argument.

Returns: 0 on success.; MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of operations was reached: see mbedtls_ecp_set_max_ops().; Another MBEDTLS_ERR_ECP_XXX error code on failure.

int mbedtls_ecdh_make_public	(	mbedtls_ecdh_context *	ctx,
		size_t *	olen,
		unsigned char *	buf,
		size_t	blen,
		int()(void , unsigned char *, size_t)	f_rng,
		void *	p_rng
	)

This function generates a public key and exports it as a TLS ClientKeyExchange payload.

This is the second function used by a TLS client for ECDH(E) ciphersuites.

See Also: ecp.h

Parameters

ctx	The ECDH context to use. This must be initialized and bound to a group, the latter usually by mbedtls_ecdh_read_params().
olen	The address at which to store the number of Bytes written. This must not be `NULL`.
buf	The destination buffer. This must be a writable buffer of length `blen` Bytes.
blen	The size of the destination buffer `buf` in Bytes.
f_rng	The RNG function to use. This must not be `NULL`.
p_rng	The RNG context to be passed to `f_rng`. This may be `NULL` in case `f_rng` doesn't need a context argument.

Returns: 0 on success.; MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of operations was reached: see mbedtls_ecp_set_max_ops().; Another MBEDTLS_ERR_ECP_XXX error code on failure.

int mbedtls_ecdh_read_params	(	mbedtls_ecdh_context *	ctx,
		const unsigned char **	buf,
		const unsigned char *	end
	)

This function parses the ECDHE parameters in a TLS ServerKeyExchange handshake message.

Note: In a TLS handshake, this is the how the client sets up its ECDHE context from the server's public ECDHE key material.

See Also: ecp.h

Parameters

ctx	The ECDHE context to use. This must be initialized.
buf	On input, `buf` must be the start of the input buffer. On output, `buf` is updated to point to the end of the data that has been read. On success, this is the first byte past the end of the ServerKeyExchange parameters. On error, this is the point at which an error has been detected, which is usually not useful except to debug failures.
end	The end of the input buffer.

Returns: 0 on success.; An MBEDTLS_ERR_ECP_XXX error code on failure.

int mbedtls_ecdh_read_public	(	mbedtls_ecdh_context *	ctx,
		const unsigned char *	buf,
		size_t	blen
	)

This function parses and processes the ECDHE payload of a TLS ClientKeyExchange message.

This is the third function used by a TLS server for ECDH(E) ciphersuites. (It is called after mbedtls_ecdh_setup() and mbedtls_ecdh_make_params().)

See Also: ecp.h

Parameters

ctx	The ECDH context to use. This must be initialized and bound to a group, for example via mbedtls_ecdh_setup().
buf	The pointer to the ClientKeyExchange payload. This must be a readable buffer of length `blen` Bytes.
blen	The length of the input buffer `buf` in Bytes.

Returns: 0 on success.; An MBEDTLS_ERR_ECP_XXX error code on failure.

int mbedtls_ecdh_setup	(	mbedtls_ecdh_context *	ctx,
		mbedtls_ecp_group_id	grp_id
	)

This function sets up the ECDH context with the information given.

This function should be called after mbedtls_ecdh_init() but before mbedtls_ecdh_make_params(). There is no need to call this function before mbedtls_ecdh_read_params().

This is the first function used by a TLS server for ECDHE ciphersuites.

Parameters

ctx	The ECDH context to set up. This must be initialized.
grp_id	The group id of the group to set up the context for.

Returns: 0 on success.

Data Structures

Macros

Typedefs

Enumerations

Functions

Detailed Description

Macro Definition Documentation

Typedef Documentation

Enumeration Type Documentation

Function Documentation