Algorithms - Diffie-Hellman

Functions
int	wc_InitDhKey (DhKey *key)
	This function initializes a Diffie-Hellman key for use in negotiating a secure secret key with the Diffie-Hellman exchange protocol. More...
void	wc_FreeDhKey (DhKey *key)
	This function frees a Diffie-Hellman key after it has been used to negotiate a secure secret key with the Diffie-Hellman exchange protocol. More...
int	wc_DhGenerateKeyPair (DhKey *key, WC_RNG *rng, byte *priv, word32 *privSz, byte *pub, word32 *pubSz)
	This function generates a public/private key pair based on the Diffie-Hellman public parameters, storing the private key in priv and the public key in pub. It takes an initialized Diffie-Hellman key and an initialized rng structure. More...
int	wc_DhAgree (DhKey *key, byte *agree, word32 *agreeSz, const byte *priv, word32 privSz, const byte *otherPub, word32 pubSz)
	This function generates an agreed upon secret key based on a local private key and a received public key. If completed on both sides of an exchange, this function generates an agreed upon secret key for symmetric communication. On successfully generating a shared secret key, the size of the secret key written will be stored in agreeSz. More...
int	wc_DhKeyDecode (const byte *input, word32 *inOutIdx, DhKey *key, word32)
	This function decodes a Diffie-Hellman key from the given input buffer containing the key in DER format. It stores the result in the DhKey structure. More...
int	wc_DhSetKey (DhKey *key, const byte *p, word32 pSz, const byte *g, word32 gSz)
	This function sets the key for a DhKey structure using the input private key parameters. Unlike wc_DhKeyDecode, this function does not require that the input key be formatted in DER format, and instead simply accepts the parsed input parameters p (prime) and g (base). More...
int	wc_DhParamsLoad (const byte *input, word32 inSz, byte *p, word32 *pInOutSz, byte *g, word32 *gInOutSz)
	This function loads the Diffie-Hellman parameters, p (prime) and g (base) out of the given input buffer, DER formatted. More...
const DhParams *	wc_Dh_ffdhe2048_Get (void)
	This function returns ... and requires that HAVE_FFDHE_2048 be defined. More...
const DhParams *	wc_Dh_ffdhe3072_Get (void)
	This function returns ... and requires that HAVE_FFDHE_3072 be defined. More...
const DhParams *	wc_Dh_ffdhe4096_Get (void)
	This function returns ... and requires that HAVE_FFDHE_4096 be defined. More...
const DhParams *	wc_Dh_ffdhe6144_Get (void)
	This function returns ... and requires that HAVE_FFDHE_6144 be defined. More...
const DhParams *	wc_Dh_ffdhe8192_Get (void)
	This function returns ... and requires that HAVE_FFDHE_8192 be defined. More...
int	wc_DhCheckKeyPair (DhKey *key, const byte *pub, word32 pubSz, const byte *priv, word32 privSz)
	Checks DH keys for pair-wise consistency per process in SP 800-56Ar3, section 5.6.2.1.4, method (b) for FFC. More...
int	wc_DhCheckPrivKey (DhKey *key, const byte *priv, word32 pubSz)
	Check DH private key for invalid numbers. More...
int	wc_DhCheckPrivKey_ex (DhKey *key, const byte *priv, word32 pubSz, const byte *prime, word32 primeSz)
int	wc_DhCheckPubKey (DhKey *key, const byte *pub, word32 pubSz)
int	wc_DhCheckPubKey_ex (DhKey *key, const byte *pub, word32 pubSz, const byte *prime, word32 primeSz)
int	wc_DhExportParamsRaw (DhKey *dh, byte *p, word32 *pSz, byte *q, word32 *qSz, byte *g, word32 *gSz)
int	wc_DhGenerateParams (WC_RNG *rng, int modSz, DhKey *dh)
int	wc_DhSetCheckKey (DhKey *key, const byte *p, word32 pSz, const byte *g, word32 gSz, const byte *q, word32 qSz, int trusted, WC_RNG *rng)
int	wc_DhSetKey_ex (DhKey *key, const byte *p, word32 pSz, const byte *g, word32 gSz, const byte *q, word32 qSz)

Detailed Description

Function Documentation

wc_Dh_ffdhe2048_Get()

const DhParams* wc_Dh_ffdhe2048_Get

(

void

)

This function returns ... and requires that HAVE_FFDHE_2048 be defined.

See also

wc_Dh_ffdhe3072_Get

wc_Dh_ffdhe4096_Get

wc_Dh_ffdhe6144_Get

wc_Dh_ffdhe8192_Get

wc_Dh_ffdhe3072_Get()

const DhParams* wc_Dh_ffdhe3072_Get

(

void

)

This function returns ... and requires that HAVE_FFDHE_3072 be defined.

See also

wc_Dh_ffdhe2048_Get

wc_Dh_ffdhe4096_Get

wc_Dh_ffdhe6144_Get

wc_Dh_ffdhe8192_Get

wc_Dh_ffdhe4096_Get()

const DhParams* wc_Dh_ffdhe4096_Get

(

void

)

This function returns ... and requires that HAVE_FFDHE_4096 be defined.

See also

wc_Dh_ffdhe2048_Get

wc_Dh_ffdhe3072_Get

wc_Dh_ffdhe6144_Get

wc_Dh_ffdhe8192_Get

wc_Dh_ffdhe6144_Get()

const DhParams* wc_Dh_ffdhe6144_Get

(

void

)

This function returns ... and requires that HAVE_FFDHE_6144 be defined.

See also

wc_Dh_ffdhe2048_Get

wc_Dh_ffdhe3072_Get

wc_Dh_ffdhe4096_Get

wc_Dh_ffdhe8192_Get

wc_Dh_ffdhe8192_Get()

const DhParams* wc_Dh_ffdhe8192_Get

(

void

)

This function returns ... and requires that HAVE_FFDHE_8192 be defined.

See also

wc_Dh_ffdhe2048_Get

wc_Dh_ffdhe3072_Get

wc_Dh_ffdhe4096_Get

wc_Dh_ffdhe6144_Get

wc_DhAgree()

int wc_DhAgree	(	DhKey *	key,
		byte *	agree,
		word32 *	agreeSz,
		const byte *	priv,
		word32	privSz,
		const byte *	otherPub,
		word32	pubSz
	)

This function generates an agreed upon secret key based on a local private key and a received public key. If completed on both sides of an exchange, this function generates an agreed upon secret key for symmetric communication. On successfully generating a shared secret key, the size of the secret key written will be stored in agreeSz.

Returns

0 Returned on successfully generating an agreed upon secret key

MP_INIT_E May be returned if there is an error while generating the shared secret key

MP_READ_E May be returned if there is an error while generating the shared secret key

MP_EXPTMOD_E May be returned if there is an error while generating the shared secret key

MP_TO_E May be returned if there is an error while generating the shared secret key

Parameters

key	pointer to the DhKey structure to use to compute the shared key
agree	pointer to the buffer in which to store the secret key
agreeSz	will hold the size of the secret key after successful generation
priv	pointer to the buffer containing the local secret key
privSz	size of the local secret key
otherPub	pointer to a buffer containing the received public key
pubSz	size of the received public key

Example

DhKey key;
int ret;
byte priv[256];
byte agree[256];
word32 agreeSz;
 
// initialize key, set key prime and base
// wc_DhGenerateKeyPair -- store private key in priv
byte pub[] = { // initialized with the received public key };
ret = wc_DhAgree(&key, agree, &agreeSz, priv, sizeof(priv), pub,
sizeof(pub));
if ( ret != 0 ) {
    // error generating shared key
}

See also

wc_DhGenerateKeyPair

wc_DhCheckKeyPair()

int wc_DhCheckKeyPair	(	DhKey *	key,
		const byte *	pub,
		word32	pubSz,
		const byte *	priv,
		word32	privSz
	)

Checks DH keys for pair-wise consistency per process in SP 800-56Ar3, section 5.6.2.1.4, method (b) for FFC.

wc_DhCheckPrivKey()

int wc_DhCheckPrivKey	(	DhKey *	key,
		const byte *	priv,
		word32	pubSz
	)

Check DH private key for invalid numbers.

wc_DhCheckPrivKey_ex()

int wc_DhCheckPrivKey_ex	(	DhKey *	key,
		const byte *	priv,
		word32	pubSz,
		const byte *	prime,
		word32	primeSz
	)

wc_DhCheckPubKey()

int wc_DhCheckPubKey	(	DhKey *	key,
		const byte *	pub,
		word32	pubSz
	)

wc_DhCheckPubKey_ex()

int wc_DhCheckPubKey_ex	(	DhKey *	key,
		const byte *	pub,
		word32	pubSz,
		const byte *	prime,
		word32	primeSz
	)

wc_DhExportParamsRaw()

int wc_DhExportParamsRaw	(	DhKey *	dh,
		byte *	p,
		word32 *	pSz,
		byte *	q,
		word32 *	qSz,
		byte *	g,
		word32 *	gSz
	)

wc_DhGenerateKeyPair()

int wc_DhGenerateKeyPair	(	DhKey *	key,
		WC_RNG *	rng,
		byte *	priv,
		word32 *	privSz,
		byte *	pub,
		word32 *	pubSz
	)

This function generates a public/private key pair based on the Diffie-Hellman public parameters, storing the private key in priv and the public key in pub. It takes an initialized Diffie-Hellman key and an initialized rng structure.

Returns

BAD_FUNC_ARG Returned if there is an error parsing one of the inputs to this function

RNG_FAILURE_E Returned if there is an error generating a random number using rng

MP_INIT_E May be returned if there is an error in the math library while generating the public key

MP_READ_E May be returned if there is an error in the math library while generating the public key

MP_EXPTMOD_E May be returned if there is an error in the math library while generating the public key

MP_TO_E May be returned if there is an error in the math library while generating the public key

Parameters

key	pointer to the DhKey structure from which to generate the key pair
rng	pointer to an initialized random number generator (rng) with which to generate the keys
priv	pointer to a buffer in which to store the private key
privSz	will store the size of the private key written to priv
pub	pointer to a buffer in which to store the public key
pubSz	will store the size of the private key written to pub

Example

DhKey key;
int ret;
byte priv[256];
byte pub[256];
word32 privSz, pubSz;
 
wc_InitDhKey(&key); // initialize key
// Set DH parameters using wc_DhSetKey or wc_DhKeyDecode
WC_RNG rng;
wc_InitRng(&rng); // initialize rng
ret = wc_DhGenerateKeyPair(&key, &rng, priv, &privSz, pub, &pubSz);

See also

wc_InitDhKey

wc_DhSetKey

wc_DhKeyDecode

wc_DhGenerateParams()

int wc_DhGenerateParams	(	WC_RNG *	rng,
		int	modSz,
		DhKey *	dh
	)

wc_DhKeyDecode()

int wc_DhKeyDecode	(	const byte *	input,
		word32 *	inOutIdx,
		DhKey *	key,
		word32
	)

This function decodes a Diffie-Hellman key from the given input buffer containing the key in DER format. It stores the result in the DhKey structure.

Returns

0 Returned on successfully decoding the input key

ASN_PARSE_E Returned if there is an error parsing the sequence of the input

ASN_DH_KEY_E Returned if there is an error reading the private key parameters from the parsed input

Parameters

input	pointer to the buffer containing the DER formatted Diffie-Hellman key
inOutIdx	pointer to an integer in which to store the index parsed to while decoding the key
key	pointer to the DhKey structure to initialize with the input key
inSz	length of the input buffer. Gives the max length that may be read

Example

DhKey key;
word32 idx = 0;
 
byte keyBuff[1024];
// initialize with DER formatted key
wc_DhKeyInit(&key);
ret = wc_DhKeyDecode(keyBuff, &idx, &key, sizeof(keyBuff));
 
if ( ret != 0 ) {
    // error decoding key
}

See also

wc_DhSetKey

wc_DhParamsLoad()

int wc_DhParamsLoad	(	const byte *	input,
		word32	inSz,
		byte *	p,
		word32 *	pInOutSz,
		byte *	g,
		word32 *	gInOutSz
	)

This function loads the Diffie-Hellman parameters, p (prime) and g (base) out of the given input buffer, DER formatted.

Returns

0 Returned on successfully extracting the DH parameters

ASN_PARSE_E Returned if an error occurs while parsing the DER formatted DH certificate

BUFFER_E Returned if there is inadequate space in p or g to store the parsed parameters

Parameters

input	pointer to a buffer containing a DER formatted Diffie-Hellman certificate to parse
inSz	size of the input buffer
p	pointer to a buffer in which to store the parsed prime
pInOutSz	pointer to a word32 object containing the available size in the p buffer. Will be overwritten with the number of bytes written to the buffer after completing the function call
g	pointer to a buffer in which to store the parsed base
gInOutSz	pointer to a word32 object containing the available size in the g buffer. Will be overwritten with the number of bytes written to the buffer after completing the function call

Example

byte dhCert[] = { initialize with DER formatted certificate };
byte p[MAX_DH_SIZE];
byte g[MAX_DH_SIZE];
word32 pSz = MAX_DH_SIZE;
word32 gSz = MAX_DH_SIZE;
 
ret = wc_DhParamsLoad(dhCert, sizeof(dhCert), p, &pSz, g, &gSz);
if ( ret != 0 ) {
    // error parsing inputs
}

See also

wc_DhSetKey

wc_DhKeyDecode

wc_DhSetCheckKey()

int wc_DhSetCheckKey	(	DhKey *	key,
		const byte *	p,
		word32	pSz,
		const byte *	g,
		word32	gSz,
		const byte *	q,
		word32	qSz,
		int	trusted,
		WC_RNG *	rng
	)

wc_DhSetKey()

int wc_DhSetKey	(	DhKey *	key,
		const byte *	p,
		word32	pSz,
		const byte *	g,
		word32	gSz
	)

This function sets the key for a DhKey structure using the input private key parameters. Unlike wc_DhKeyDecode, this function does not require that the input key be formatted in DER format, and instead simply accepts the parsed input parameters p (prime) and g (base).

Returns

0 Returned on successfully setting the key

BAD_FUNC_ARG Returned if any of the input parameters evaluate to NULL

MP_INIT_E Returned if there is an error initializing the key parameters for storage

ASN_DH_KEY_E Returned if there is an error reading in the DH key parameters p and g

Parameters

key	pointer to the DhKey structure on which to set the key
p	pointer to the buffer containing the prime for use with the key
pSz	length of the input prime
g	pointer to the buffer containing the base for use with the key
gSz	length of the input base

Example

DhKey key;
 
byte p[] = { // initialize with prime };
byte g[] = { // initialize with base };
wc_DhKeyInit(&key);
ret = wc_DhSetKey(key, p, sizeof(p), g, sizeof(g));
 
if ( ret != 0 ) {
    // error setting key
}

See also

wc_DhKeyDecode

wc_DhSetKey_ex()

int wc_DhSetKey_ex	(	DhKey *	key,
		const byte *	p,
		word32	pSz,
		const byte *	g,
		word32	gSz,
		const byte *	q,
		word32	qSz
	)

wc_FreeDhKey()

int wc_FreeDhKey

(

DhKey *

key

)

This function frees a Diffie-Hellman key after it has been used to negotiate a secure secret key with the Diffie-Hellman exchange protocol.

Returns

none No returns.

Parameters

key	pointer to the DhKey structure to free

Example

DhKey key;
// initialize key, perform key exchange
 
wc_FreeDhKey(&key); // free DH key to avoid memory leaks

See also

wc_InitDhKey

wc_InitDhKey()

int wc_InitDhKey

(

DhKey *

key

)

This function initializes a Diffie-Hellman key for use in negotiating a secure secret key with the Diffie-Hellman exchange protocol.

Returns

none No returns.

Parameters

key	pointer to the DhKey structure to initialize for use with secure key exchanges

Example

DhKey key;
wc_InitDhKey(&key); // initialize DH key

See also

wc_FreeDhKey

wc_DhGenerateKeyPair