Algorithms - DSA

Functions
int	wc_InitDsaKey (DsaKey *key)
	This function initializes a DsaKey object in order to use it for authentication via the Digital Signature Algorithm (DSA). More...
void	wc_FreeDsaKey (DsaKey *key)
	This function frees a DsaKey object after it has been used. More...
int	wc_DsaSign (const byte *digest, byte *out, DsaKey *key, WC_RNG *rng)
	This function signs the input digest and stores the result in the output buffer, out. More...
int	wc_DsaVerify (const byte *digest, const byte *sig, DsaKey *key, int *answer)
	This function verifies the signature of a digest, given a private key. It stores whether the key properly verifies in the answer parameter, with 1 corresponding to a successful verification, and 0 corresponding to failed verification. More...
int	wc_DsaPublicKeyDecode (const byte *input, word32 *inOutIdx, DsaKey *key, word32 inSz)
	This function decodes a DER formatted certificate buffer containing a DSA public key, and stores the key in the given DsaKey structure. It also sets the inOutIdx parameter according to the length of the input read. More...
int	wc_DsaPrivateKeyDecode (const byte *input, word32 *inOutIdx, DsaKey *key, word32 inSz)
	This function decodes a DER formatted certificate buffer containing a DSA private key, and stores the key in the given DsaKey structure. It also sets the inOutIdx parameter according to the length of the input read. More...
int	wc_DsaKeyToDer (DsaKey *key, byte *output, word32 inLen)
	Convert DsaKey key to DER format, write to output (inLen), return bytes written. More...
int	wc_MakeDsaKey (WC_RNG *rng, DsaKey *dsa)
	Create a DSA key. More...
int	wc_MakeDsaParameters (WC_RNG *rng, int modulus_size, DsaKey *dsa)
	FIPS 186-4 defines valid for modulus_size values as (1024, 160) (2048, 256) (3072, 256) More...

Detailed Description

Function Documentation

wc_DsaKeyToDer()

int wc_DsaKeyToDer	(	DsaKey *	key,
		byte *	output,
		word32	inLen
	)

Convert DsaKey key to DER format, write to output (inLen), return bytes written.

Returns

outLen Success, number of bytes written

BAD_FUNC_ARG key or output are null or key->type is not DSA_PRIVATE.

MEMORY_E Error allocating memory.

Parameters

key	Pointer to DsaKey structure to convert.
output	Pointer to output buffer for converted key.
inLen	Length of key input.

Example

DsaKey key;
WC_RNG rng;
int derSz;
int bufferSize = // Sufficient buffer size;
byte der[bufferSize];
 
wc_InitDsaKey(&key);
wc_InitRng(&rng);
wc_MakeDsaKey(&rng, &key);
derSz = wc_DsaKeyToDer(&key, der, bufferSize);

See also

wc_InitDsaKey

wc_FreeDsaKey

wc_MakeDsaKey

wc_DsaPrivateKeyDecode()

int wc_DsaPrivateKeyDecode	(	const byte *	input,
		word32 *	inOutIdx,
		DsaKey *	key,
		word32	inSz
	)

This function decodes a DER formatted certificate buffer containing a DSA private key, and stores the key in the given DsaKey structure. It also sets the inOutIdx parameter according to the length of the input read.

Returns

0 Returned on successfully setting the private key for the DsaKey object

ASN_PARSE_E Returned if there is an error in the encoding while reading the certificate buffer

ASN_DH_KEY_E Returned if one of the DSA parameters is incorrectly formatted

Parameters

input	pointer to the buffer containing the DER formatted DSA private key
inOutIdx	pointer to an integer in which to store the final index of the certificate read
key	pointer to the DsaKey structure in which to store the private key
inSz	size of the input buffer

Example

int ret, idx=0;
 
DsaKey key;
wc_InitDsaKey(&key);
byte derBuff[] = { // DSA private key };
ret = wc_DsaPrivateKeyDecode(derBuff, &idx, &key, inSz);
if (ret != 0) {
    // error reading private key
}

See also

wc_InitDsaKey

wc_DsaPublicKeyDecode

wc_DsaPublicKeyDecode()

int wc_DsaPublicKeyDecode	(	const byte *	input,
		word32 *	inOutIdx,
		DsaKey *	key,
		word32	inSz
	)

This function decodes a DER formatted certificate buffer containing a DSA public key, and stores the key in the given DsaKey structure. It also sets the inOutIdx parameter according to the length of the input read.

Returns

0 Returned on successfully setting the public key for the DsaKey object

ASN_PARSE_E Returned if there is an error in the encoding while reading the certificate buffer

ASN_DH_KEY_E Returned if one of the DSA parameters is incorrectly formatted

Parameters

input	pointer to the buffer containing the DER formatted DSA public key
inOutIdx	pointer to an integer in which to store the final index of the certificate read
key	pointer to the DsaKey structure in which to store the public key
inSz	size of the input buffer

Example

int ret, idx=0;
 
DsaKey key;
wc_InitDsaKey(&key);
byte derBuff[] = { // DSA public key};
ret = wc_DsaPublicKeyDecode(derBuff, &idx, &key, inSz);
if (ret != 0) {
    // error reading public key
}

See also

wc_InitDsaKey

wc_DsaPrivateKeyDecode

wc_DsaSign()

int wc_DsaSign	(	const byte *	digest,
		byte *	out,
		DsaKey *	key,
		WC_RNG *	rng
	)

This function signs the input digest and stores the result in the output buffer, out.

Returns

0 Returned on successfully signing the input digest

MP_INIT_E may be returned if there is an error in processing the DSA signature.

MP_READ_E may be returned if there is an error in processing the DSA signature.

MP_CMP_E may be returned if there is an error in processing the DSA signature.

MP_INVMOD_E may be returned if there is an error in processing the DSA signature.

MP_EXPTMOD_E may be returned if there is an error in processing the DSA signature.

MP_MOD_E may be returned if there is an error in processing the DSA signature.

MP_MUL_E may be returned if there is an error in processing the DSA signature.

MP_ADD_E may be returned if there is an error in processing the DSA signature.

MP_MULMOD_E may be returned if there is an error in processing the DSA signature.

MP_TO_E may be returned if there is an error in processing the DSA signature.

MP_MEM may be returned if there is an error in processing the DSA signature.

Parameters

digest	pointer to the hash to sign
out	pointer to the buffer in which to store the signature
key	pointer to the initialized DsaKey structure with which to generate the signature
rng	pointer to an initialized RNG to use with the signature generation

Example

DsaKey key;
// initialize DSA key, load private Key
int ret;
WC_RNG rng;
wc_InitRng(&rng);
byte hash[] = { // initialize with hash digest };
byte signature[40]; // signature will be 40 bytes (320 bits)
 
ret = wc_DsaSign(hash, signature, &key, &rng);
if (ret != 0) {
    // error generating DSA signature
}

See also

wc_DsaVerify

wc_DsaVerify()

int wc_DsaVerify	(	const byte *	digest,
		const byte *	sig,
		DsaKey *	key,
		int *	answer
	)

This function verifies the signature of a digest, given a private key. It stores whether the key properly verifies in the answer parameter, with 1 corresponding to a successful verification, and 0 corresponding to failed verification.

Returns

0 Returned on successfully processing the verify request. Note: this does not mean that the signature is verified, only that the function succeeded

MP_INIT_E may be returned if there is an error in processing the DSA signature.

MP_READ_E may be returned if there is an error in processing the DSA signature.

MP_CMP_E may be returned if there is an error in processing the DSA signature.

MP_INVMOD_E may be returned if there is an error in processing the DSA signature.

MP_EXPTMOD_E may be returned if there is an error in processing the DSA signature.

MP_MOD_E may be returned if there is an error in processing the DSA signature.

MP_MUL_E may be returned if there is an error in processing the DSA signature.

MP_ADD_E may be returned if there is an error in processing the DSA signature.

MP_MULMOD_E may be returned if there is an error in processing the DSA signature.

MP_TO_E may be returned if there is an error in processing the DSA signature.

MP_MEM may be returned if there is an error in processing the DSA signature.

Parameters

digest	pointer to the digest containing the subject of the signature
sig	pointer to the buffer containing the signature to verify
key	pointer to the initialized DsaKey structure with which to verify the signature
answer	pointer to an integer which will store whether the verification was successful

Example

DsaKey key;
// initialize DSA key, load public Key
 
int ret;
int verified;
byte hash[] = { // initialize with hash digest };
byte signature[] = { // initialize with signature to verify };
ret = wc_DsaVerify(hash, signature, &key, &verified);
if (ret != 0) {
    // error processing verify request
} else if (answer == 0) {
    // invalid signature
}

See also

wc_DsaSign

wc_FreeDsaKey()

void wc_FreeDsaKey

(

DsaKey *

key

)

This function frees a DsaKey object after it has been used.

Returns

none No returns.

Parameters

key	pointer to the DsaKey structure to free

Example

DsaKey key;
// initialize key, use for authentication
...
wc_FreeDsaKey(&key); // free DSA key

See also

wc_FreeDsaKey

wc_InitDsaKey()

int wc_InitDsaKey

(

DsaKey *

key

)

This function initializes a DsaKey object in order to use it for authentication via the Digital Signature Algorithm (DSA).

Returns

0 Returned on success.

BAD_FUNC_ARG Returned if a NULL key is passed in.

Parameters

key	pointer to the DsaKey structure to initialize

Example

DsaKey key;
int ret;
ret = wc_InitDsaKey(&key); // initialize DSA key

See also

wc_FreeDsaKey

wc_MakeDsaKey()

int wc_MakeDsaKey	(	WC_RNG *	rng,
		DsaKey *	dsa
	)

Create a DSA key.

Returns

MP_OKAY Success

BAD_FUNC_ARG Either rng or dsa is null.

MEMORY_E Couldn't allocate memory for buffer.

MP_INIT_E Error initializing mp_int

Parameters

rng	Pointer to WC_RNG structure.
dsa	Pointer to DsaKey structure.

Example

WC_RNG rng;
DsaKey dsa;
wc_InitRng(&rng);
wc_InitDsa(&dsa);
if(wc_MakeDsaKey(&rng, &dsa) != 0)
{
    // Error creating key
}

See also

wc_InitDsaKey

wc_FreeDsaKey

wc_DsaSign

wc_MakeDsaParameters()

int wc_MakeDsaParameters	(	WC_RNG *	rng,
		int	modulus_size,
		DsaKey *	dsa
	)

FIPS 186-4 defines valid for modulus_size values as (1024, 160) (2048, 256) (3072, 256)

Returns

0 Success

BAD_FUNC_ARG rng or dsa is null or modulus_size is invalid.

MEMORY_E Error attempting to allocate memory.

Parameters

rng	pointer to wolfCrypt rng.
modulus_size	1024, 2048, or 3072 are valid values.
dsa	Pointer to a DsaKey structure.

Example

DsaKey key;
WC_RNG rng;
wc_InitDsaKey(&key);
wc_InitRng(&rng);
if(wc_MakeDsaParameters(&rng, 1024, &genKey) != 0)
{
    // Handle error
}

See also

wc_MakeDsaKey

wc_DsaKeyToDer

wc_InitDsaKey