Re: [PATCH 4/6] crypto: ecdsa: add ECDSA SW implementation

[Nitin Kumbhar <nkumbhar@nvidia.com>]

Hello Stephan,

On 1/20/2017 6:36 PM, Stephan Müller wrote:
> Am Freitag, 20. Januar 2017, 17:05:59 CET schrieb Nitin Kumbhar:
>
> Hi Nitin,
>
>> This adds support for ECDSA algorithm. This implementation supports
>> sign and verify functions for ECDSA algorithm using akcipher. As ECDSA
>> is a signing algorithm dummy functions are added for encrypt() and
>> decrypt().
>>
>> Helper routines for parsing public and private ECC keys for ECDSA are
>> added as well.
>>
>> Signed-off-by: Nitin Kumbhar <nkumbhar@nvidia.com>
>> ---
>>  crypto/Kconfig            |    7 +
>>  crypto/Makefile           |    3 +
>>  crypto/ecdsa.c            |  331
>> +++++++++++++++++++++++++++++++++++++++++++++ crypto/ecdsa_helper.c     |
>> 116 ++++++++++++++++
>>  include/crypto/akcipher.h |    5 +-
>>  include/crypto/ecdsa.h    |   29 ++++
>>  6 files changed, 490 insertions(+), 1 deletions(-)
>>  create mode 100644 crypto/ecdsa.c
>>  create mode 100644 crypto/ecdsa_helper.c
>>  create mode 100644 include/crypto/ecdsa.h
>>
>> diff --git a/crypto/Kconfig b/crypto/Kconfig
>> index e240075d6f46..1c5c236b3bbc 100644
>> --- a/crypto/Kconfig
>> +++ b/crypto/Kconfig
>> @@ -140,6 +140,13 @@ config CRYPTO_ECDH
>>  	help
>>  	  Generic implementation of the ECDH algorithm
>>
>> +config CRYPTO_ECDSA
>> +	tristate "ECDSA algorithm"
>> +	select CRYPTO_AKCIPHER
>> +	select CRYPTO_ECC
>> +	help
>> +	  Generic implementation of the ECDSA algorithm
>> +
>>  config CRYPTO_MANAGER
>>  	tristate "Cryptographic algorithm manager"
>>  	select CRYPTO_MANAGER2
>> diff --git a/crypto/Makefile b/crypto/Makefile
>> index 827740a47a37..9c13eb2ade6a 100644
>> --- a/crypto/Makefile
>> +++ b/crypto/Makefile
>> @@ -38,6 +38,9 @@ obj-$(CONFIG_CRYPTO_ECC) += ecc.o
>>  ecdh_generic-y := ecdh.o
>>  ecdh_generic-y += ecdh_helper.o
>>  obj-$(CONFIG_CRYPTO_ECDH) += ecdh_generic.o
>> +ecdsa_generic-y := ecdsa.o
>> +ecdsa_generic-y += ecdsa_helper.o
>> +obj-$(CONFIG_CRYPTO_ECDSA) += ecdsa_generic.o
>>
>>  $(obj)/rsapubkey-asn1.o: $(obj)/rsapubkey-asn1.c $(obj)/rsapubkey-asn1.h
>>  $(obj)/rsaprivkey-asn1.o: $(obj)/rsaprivkey-asn1.c $(obj)/rsaprivkey-asn1.h
>> diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c
>> new file mode 100644
>> index 000000000000..d415900af3bd
>> --- /dev/null
>> +++ b/crypto/ecdsa.c
>> @@ -0,0 +1,331 @@
>> +/*
>> + * ECDSA generic algorithm
>> + *
>> + * Copyright (c) 2017, NVIDIA Corporation. All Rights Reserved.
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms of the GNU General Public License as published by the
>> Free + * Software Foundation; either version 2 of the License, or (at your
>> option) + * any later version.
>> + *
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/scatterlist.h>
>> +#include <linux/random.h>
>> +#include <crypto/internal/akcipher.h>
>> +#include <crypto/akcipher.h>
>> +#include <crypto/ecdsa.h>
>> +
>> +#include "ecc.h"
>> +
>> +struct ecdsa_ctx {
>> +	unsigned int curve_id;
>> +	unsigned int ndigits;
>> +	u64 private_key[ECC_MAX_DIGITS];
>> +	u64 public_key[2 * ECC_MAX_DIGITS];
>> +};
>> +
>> +static inline struct ecdsa_ctx *ecdsa_get_ctx(struct crypto_akcipher *tfm)
>> +{
>> +	return akcipher_tfm_ctx(tfm);
>> +}
>> +
>> +static void ecdsa_parse_msg_hash(struct akcipher_request *req, u64 *msg,
>> +				 unsigned int ndigits)
>> +{
>> +	unsigned int nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
>> +	unsigned int hash_len, hash_off;
>> +	unsigned char *hash, *msg_ptr;
>> +	int i;
>> +
>> +	/*
>> +	 * If hash_len == nbytes:
>> +	 *	copy nbytes from req
>> +	 * If hash_len > nbytes:
>> +	 *	copy left most nbytes from hash ignoring LSBs
>> +	 * If hash_len < nbytes:
>> +	 *	copy hash_len from req and zero remaining bytes
>> +	 *	(nbytes - hash_len)
>> +	 */
>> +	hash_len = req->src[0].length;
>> +	hash_off = hash_len <= nbytes ? 0 : hash_len - nbytes;
>> +
>> +	msg_ptr = (unsigned char *)msg;
>> +	hash = sg_virt(&req->src[0]);
>> +
>> +	for (i = hash_off; i < hash_len; i++)
>> +		*msg_ptr++ = hash[i];
>> +	for (; i < nbytes; i++)
>> +		*msg_ptr++ = 0;
>> +}
>> +
>> +int ecdsa_sign(struct akcipher_request *req)
>> +{
>> +	struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
>> +	struct ecdsa_ctx *ctx = ecdsa_get_ctx(tfm);
>> +	unsigned int ndigits = ctx->ndigits;
>> +	unsigned int nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
>> +	unsigned int curve_id = ctx->curve_id;
>> +	const struct ecc_curve *curve = ecc_get_curve(curve_id);
>> +	struct ecc_point *x1y1 = NULL;
>> +	u64 z[ndigits], d[ndigits];
>> +	u64 k[ndigits], k_inv[ndigits];
>> +	u64 r[ndigits], s[ndigits];
>> +	u64 dr[ndigits], zdr[ndigits];
>> +	u8 *r_ptr, *s_ptr;
>> +
>> +	if (req->dst_len < 2 * nbytes) {
>> +		req->dst_len = 2 * nbytes;
>> +		return -EINVAL;
>> +	}
>> +
>> +	ecdsa_parse_msg_hash(req, z, ndigits);
>> +
>> +	/* d */
>> +	vli_set(d, (const u64 *)ctx->private_key, ndigits);
>> +
>> +	/* k */
>> +#if defined(CONFIG_CRYPTO_MANAGER2)
>> +	if (req->info) {
>> +		vli_copy_from_buf(k, ndigits, req->info, nbytes);
>> +	} else
>> +#endif
>> +		get_random_bytes(k, nbytes);
>
> Please use crypto_get_default_rng /crypto_rng_get_bytes /
> crypto_put_default_rng here.

Sure. I will update that in next version of the patch.

>> +
>> +	x1y1 = ecc_alloc_point(ndigits);
>> +	if (!x1y1)
>> +		return -ENOMEM;
>> +
>> +	/* (x1, y1) = k x G */
>> +	ecc_point_mult(x1y1, &curve->g, k, NULL, curve->p, ndigits);
>> +
>> +	/* r = x1 mod n */
>> +	vli_mod(r, x1y1->x, curve->n, ndigits);
>> +
>> +	/* k^-1 */
>> +	vli_mod_inv(k_inv, k, curve->n, ndigits);
>> +
>> +	/* d . r mod n */
>> +	vli_mod_mult(dr, d, r, curve->n, ndigits);
>> +
>> +	/* z + dr mod n */
>> +	vli_mod_add(zdr, z, dr, curve->n, ndigits);
>> +
>> +	/* k^-1 . ( z + dr) mod n */
>> +	vli_mod_mult(s, k_inv, zdr, curve->n, ndigits);
>> +
>> +	/* write signature (r,s) in dst */
>> +	r_ptr = sg_virt(req->dst);
>> +	s_ptr = (u8 *)sg_virt(req->dst) + nbytes;
>> +
>> +	vli_copy_to_buf(r_ptr, nbytes, r, ndigits);
>> +	vli_copy_to_buf(s_ptr, nbytes, s, ndigits);
>> +
>> +	req->dst_len = 2 * nbytes;
>> +
>> +	ecc_free_point(x1y1);
>> +	return 0;
>> +}
>> +
>> +int ecdsa_verify(struct akcipher_request *req)
>> +{
>> +	struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
>> +	struct ecdsa_ctx *ctx = ecdsa_get_ctx(tfm);
>> +	unsigned int ndigits = ctx->ndigits;
>> +	unsigned int nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
>> +	unsigned int curve_id = ctx->curve_id;
>> +	const struct ecc_curve *curve = ecc_get_curve(curve_id);
>> +	struct ecc_point *x1y1 = NULL, *x2y2 = NULL, *Q = NULL;
>> +	u64 r[ndigits], s[ndigits], v[ndigits];
>> +	u64 z[ndigits], w[ndigits];
>> +	u64 u1[ndigits], u2[ndigits];
>> +	u64 x1[ndigits], x2[ndigits];
>> +	u64 y1[ndigits], y2[ndigits];
>> +	u64 *ctx_qx, *ctx_qy;
>> +	int ret;
>> +
>> +	x1y1 = ecc_alloc_point(ndigits);
>> +	x2y2 = ecc_alloc_point(ndigits);
>> +	Q = ecc_alloc_point(ndigits);
>> +	if (!x1y1 || !x2y2 || !Q) {
>> +		ret = -ENOMEM;
>> +		goto exit;
>> +	}
>> +
>> +	ecdsa_parse_msg_hash(req, z, ndigits);
>> +
>> +	/* Signature r,s */
>> +	vli_copy_from_buf(r, ndigits, sg_virt(&req->src[1]), nbytes);
>> +	vli_copy_from_buf(s, ndigits, sg_virt(&req->src[2]), nbytes);
>> +
>> +	/* w = s^-1 mod n */
>> +	vli_mod_inv(w, s, curve->n, ndigits);
>> +
>> +	/* u1 = zw mod n */
>> +	vli_mod_mult(u1, z, w, curve->n, ndigits);
>> +
>> +	/* u2 = rw mod n */
>> +	vli_mod_mult(u2, r, w, curve->n, ndigits);
>> +
>> +	/* u1 . G */
>> +	ecc_point_mult(x1y1, &curve->g, u1, NULL, curve->p, ndigits);
>> +
>> +	/* Q=(Qx,Qy) */
>> +	ctx_qx = ctx->public_key;
>> +	ctx_qy = ctx_qx + ECC_MAX_DIGITS;
>> +	vli_set(Q->x, ctx_qx, ndigits);
>> +	vli_set(Q->y, ctx_qy, ndigits);
>> +
>> +	/* u2 x Q */
>> +	ecc_point_mult(x2y2, Q, u2, NULL, curve->p, ndigits);
>> +
>> +	vli_set(x1, x1y1->x, ndigits);
>> +	vli_set(y1, x1y1->y, ndigits);
>> +	vli_set(x2, x2y2->x, ndigits);
>> +	vli_set(y2, x2y2->y, ndigits);
>> +
>> +	/* x1y1 + x2y2 => P + Q; P + Q in x2 y2 */
>> +	ecc_point_add(x1, y1, x2, y2, curve->p, ndigits);
>> +
>> +	/* v = x mod n */
>> +	vli_mod(v, x2, curve->n, ndigits);
>> +
>> +	/* validate signature */
>> +	ret = vli_cmp(v, r, ndigits) == 0 ? 0 : -EBADMSG;
>> + exit:
>> +	ecc_free_point(x1y1);
>> +	ecc_free_point(x2y2);
>> +	ecc_free_point(Q);
>> +	return ret;
>> +}
>> +
>> +int ecdsa_dummy_enc(struct akcipher_request *req)
>> +{
>> +	return -EINVAL;
>> +}
>> +
>> +int ecdsa_dummy_dec(struct akcipher_request *req)
>> +{
>> +	return -EINVAL;
>> +}
>> +
>> +int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
>> +		      unsigned int keylen)
>> +{
>> +	struct ecdsa_ctx *ctx = ecdsa_get_ctx(tfm);
>> +	struct ecdsa params;
>> +	unsigned int ndigits;
>> +	unsigned int nbytes;
>> +	u8 *params_qx, *params_qy;
>> +	u64 *ctx_qx, *ctx_qy;
>> +	int ret = 0;
>> +
>> +	if (crypto_ecdsa_parse_pub_key(key, keylen, &params))
>> +		return -EINVAL;
>> +
>> +	ndigits = ecdsa_supported_curve(params.curve_id);
>> +
>> +	ctx->curve_id = params.curve_id;
>> +	ctx->ndigits = ndigits;
>> +	nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
>> +
>> +	params_qx = params.key;
>> +	params_qy = params_qx + ECC_MAX_DIGIT_BYTES;
>> +
>> +	ctx_qx = ctx->public_key;
>> +	ctx_qy = ctx_qx + ECC_MAX_DIGITS;
>> +
>> +	vli_copy_from_buf(ctx_qx, ndigits, params_qx, nbytes);
>> +	vli_copy_from_buf(ctx_qy, ndigits, params_qy, nbytes);
>> +
>> +	memset(&params, 0, sizeof(params));
>> +	return ret;
>
> Shouldn't there be a check that the point is on the curve? As I think the same
> issue is applicable to ECDH, I guess a common service function should be used
> that we can also invoke from ECDH.

Yes. I'll add checks for public key.

>> +}
>> +
>> +int ecdsa_set_priv_key(struct crypto_akcipher *tfm, const void *key,
>> +		       unsigned int keylen)
>> +{
>> +	struct ecdsa_ctx *ctx = ecdsa_get_ctx(tfm);
>> +	struct ecdsa params;
>> +	unsigned int ndigits;
>> +	unsigned int nbytes;
>> +
>> +	if (crypto_ecdsa_parse_priv_key(key, keylen, &params))
>> +		return -EINVAL;
>> +
>> +	ndigits = ecdsa_supported_curve(params.curve_id);
>> +
>> +	ctx->curve_id = params.curve_id;
>> +	ctx->ndigits = ndigits;
>> +	nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
>> +
>> +	if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
>> +			     (const u8 *)params.key, params.key_size) < 0)
>> +		return -EINVAL;
>> +
>> +	vli_copy_from_buf(ctx->private_key, ndigits, params.key, nbytes);
>> +
>> +	memset(&params, 0, sizeof(params));
>> +	return 0;
>> +}
>> +
>> +int ecdsa_max_size(struct crypto_akcipher *tfm)
>> +{
>> +	struct ecdsa_ctx *ctx = ecdsa_get_ctx(tfm);
>> +	int nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
>> +
>> +	/* For r,s */
>> +	return 2 * nbytes;
>> +}
>> +
>> +int ecdsa_init_tfm(struct crypto_akcipher *tfm)
>> +{
>> +	return 0;
>> +}
>> +
>> +void ecdsa_exit_tfm(struct crypto_akcipher *tfm)
>> +{
>> +}
>> +
>> +static struct akcipher_alg ecdsa_alg = {
>> +	.sign		= ecdsa_sign,
>> +	.verify		= ecdsa_verify,
>> +	.encrypt	= ecdsa_dummy_enc,
>> +	.decrypt	= ecdsa_dummy_dec,
>> +	.set_priv_key	= ecdsa_set_priv_key,
>> +	.set_pub_key	= ecdsa_set_pub_key,
>> +	.max_size	= ecdsa_max_size,
>> +	.init		= ecdsa_init_tfm,
>> +	.exit		= ecdsa_exit_tfm,
>> +	.base = {
>> +		.cra_name	= "ecdsa",
>> +		.cra_driver_name = "ecdsa-generic",
>> +		.cra_priority	= 100,
>> +		.cra_module	= THIS_MODULE,
>> +		.cra_ctxsize	= sizeof(struct ecdsa_ctx),
>> +	},
>> +};
>> +
>> +static int ecdsa_init(void)
>> +{
>> +	int ret;
>> +
>> +	ret = crypto_register_akcipher(&ecdsa_alg);
>> +	if (ret)
>> +		pr_err("ecdsa alg register failed. err:%d\n", ret);
>> +	return ret;
>> +}
>> +
>> +static void ecdsa_exit(void)
>> +{
>> +	crypto_unregister_akcipher(&ecdsa_alg);
>> +}
>> +
>> +module_init(ecdsa_init);
>> +module_exit(ecdsa_exit);
>> +
>> +MODULE_ALIAS_CRYPTO("ecdsa");
>> +MODULE_LICENSE("GPL");
>> +MODULE_DESCRIPTION("ECDSA Generic Algorithm");
>> +MODULE_AUTHOR("NVIDIA Corporation");
>> diff --git a/crypto/ecdsa_helper.c b/crypto/ecdsa_helper.c
>> new file mode 100644
>> index 000000000000..d31eb54431a9
>> --- /dev/null
>> +++ b/crypto/ecdsa_helper.c
>> @@ -0,0 +1,116 @@
>> +/*
>> + * ECDSA helper routines
>> + *
>> + * Copyright (c) 2017, NVIDIA Corporation. All Rights Reserved.
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms of the GNU General Public License as published by the
>> Free + * Software Foundation; either version 2 of the License, or (at your
>> option) + * any later version.
>> + *
>> + */
>> +
>> +#include <linux/kernel.h>
>> +#include <linux/export.h>
>> +#include <linux/err.h>
>> +#include <linux/string.h>
>> +#include <crypto/ecdsa.h>
>> +
>> +#include "ecc.h"
>> +
>> +#define ECDSA_KEY_MIN_SIZE	(1 + 1 + 24) /* ver + cid + n (P-192) */
>> +
>> +unsigned int ecdsa_supported_curve(unsigned int curve_id)
>> +{
>> +	switch (curve_id) {
>> +	case ECC_CURVE_NIST_P192: return 3;
>> +	case ECC_CURVE_NIST_P256: return 4;
>> +	default: return 0;
>> +	}
>> +}
>
> Wouldn't it be better to have a common function with ECDH as this has almost
> the same code in ecdh_supported_curve?

A separate function is added as ECDH and ECDSA may not support all 
elliptic curves. This allows to handle the differences.

>> +
>> +static inline u8 *ecdsa_pack_data(void *dst, const void *src, size_t sz)
>> +{
>> +	memcpy(dst, src, sz);
>> +	return dst + sz;
>> +}
>> +
>> +static inline const u8 *ecdsa_unpack_data(void *dst, const void *src,
>> size_t sz) +{
>> +	memcpy(dst, src, sz);
>> +	return src + sz;
>> +}
>> +
>> +int crypto_ecdsa_parse_pub_key(const char *buf, unsigned int len,
>> +			       struct ecdsa *params)
>> +{
>> +	unsigned char version;
>> +	unsigned int ndigits;
>> +	unsigned int nbytes;
>> +	const u8 *ptr = buf;
>> +	u8 *qx, *qy;
>> +
>> +	if (unlikely(!buf) || len < ECDSA_KEY_MIN_SIZE)
>> +		return -EINVAL;
>> +
>> +	ptr = ecdsa_unpack_data(&version, ptr, sizeof(version));
>> +	if (version != 1)
>> +		return -EINVAL;
>> +
>> +	ptr = ecdsa_unpack_data(&params->curve_id, ptr,
>> +				sizeof(params->curve_id));
>> +
>> +	ndigits = ecdsa_supported_curve(params->curve_id);
>> +	if (!ndigits)
>> +		return -EINVAL;
>> +
>> +	nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
>> +
>> +	/* skip private key */
>> +	ptr = ecdsa_unpack_data(&params->key, ptr, nbytes);
>> +
>> +	/* copy public key */
>> +	qx = params->key;
>> +	qy = qx + ECC_MAX_DIGIT_BYTES;
>> +
>> +	ptr = ecdsa_unpack_data(qx, ptr, nbytes);
>> +	ptr = ecdsa_unpack_data(qy, ptr, nbytes);
>> +
>> +	params->key_size = 2 * nbytes;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(crypto_ecdsa_parse_pub_key);
>> +
>> +int crypto_ecdsa_parse_priv_key(const char *buf, unsigned int len,
>> +				struct ecdsa *params)
>> +{
>> +	unsigned char version;
>> +	unsigned int ndigits;
>> +	unsigned int nbytes;
>> +	const u8 *ptr = buf;
>> +
>> +	if (unlikely(!buf) || len < ECDSA_KEY_MIN_SIZE)
>> +		return -EINVAL;
>> +
>> +	ptr = ecdsa_unpack_data(&version, ptr, sizeof(version));
>> +	if (version != 1)
>> +		return -EINVAL;
>> +
>> +	ptr = ecdsa_unpack_data(&params->curve_id, ptr,
>> +				sizeof(params->curve_id));
>> +
>> +	ndigits = ecdsa_supported_curve(params->curve_id);
>> +	if (!ndigits)
>> +		return -EINVAL;
>> +
>> +	nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
>> +
>> +	params->key_size = nbytes;
>> +
>> +	/* copy private key */
>> +	ptr = ecdsa_unpack_data(&params->key, ptr, nbytes);
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(crypto_ecdsa_parse_priv_key);
>> diff --git a/include/crypto/akcipher.h b/include/crypto/akcipher.h
>> index c37cc59e9bf2..6b34e9043a6f 100644
>> --- a/include/crypto/akcipher.h
>> +++ b/include/crypto/akcipher.h
>> @@ -3,6 +3,7 @@
>>   *
>>   * Copyright (c) 2015, Intel Corporation
>>   * Authors: Tadeusz Struk <tadeusz.struk@intel.com>
>> + * Copyright (c) 2017, NVIDIA Corporation. All Rights Reserved.
>>   *
>>   * This program is free software; you can redistribute it and/or modify it
>>   * under the terms of the GNU General Public License as published by the
>> Free @@ -27,6 +28,7 @@
>>   *		result.
>>   *		In case of error where the dst sgl size was insufficient,
>>   *		it will be updated to the size required for the operation.
>> + * @info:	Any request specific data needed to process the request.
>>   * @__ctx:	Start of private context data
>>   */
>>  struct akcipher_request {
>> @@ -35,6 +37,7 @@ struct akcipher_request {
>>  	struct scatterlist *dst;
>>  	unsigned int src_len;
>>  	unsigned int dst_len;
>> +	void *info;
>>  	void *__ctx[] CRYPTO_MINALIGN_ATTR;
>>  };
>>
>> @@ -193,7 +196,7 @@ static inline void crypto_free_akcipher(struct
>> crypto_akcipher *tfm) {
>>  	struct akcipher_request *req;
>>
>> -	req = kmalloc(sizeof(*req) + crypto_akcipher_reqsize(tfm), gfp);
>> +	req = kzalloc(sizeof(*req) + crypto_akcipher_reqsize(tfm), gfp);
>>  	if (likely(req))
>>  		akcipher_request_set_tfm(req, tfm);
>>
>> diff --git a/include/crypto/ecdsa.h b/include/crypto/ecdsa.h
>> new file mode 100644
>> index 000000000000..c71d21e654b9
>> --- /dev/null
>> +++ b/include/crypto/ecdsa.h
>> @@ -0,0 +1,29 @@
>> +/*
>> + * ECC parameters for ECDSA
>> + *
>> + * Copyright (c) 2017, NVIDIA Corporation. All Rights Reserved.
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms of the GNU General Public License as published by the
>> Free + * Software Foundation; either version 2 of the License, or (at your
>> option) + * any later version.
>> + *
>> + */
>> +
>> +#ifndef _CRYPTO_ECDSA_
>> +#define _CRYPTO_ECDSA_
>> +
>> +#include <crypto/ecc.h>
>> +
>> +struct ecdsa {
>> +	unsigned char curve_id;
>> +	unsigned char key[2 * ECC_MAX_DIGIT_BYTES];
>> +	unsigned short key_size;
>> +};
>> +
>> +unsigned int ecdsa_supported_curve(unsigned int curve_id);
>> +int crypto_ecdsa_parse_pub_key(const char *buf, unsigned int len,
>> +			       struct ecdsa *params);
>> +int crypto_ecdsa_parse_priv_key(const char *buf, unsigned int len,
>> +				struct ecdsa *params);
>> +#endif /* _CRYPTO_ECDSA_ */
>
> I would like to see soem documentation here similar to the ecdh.h. Especially,
> can you please add documentation which type of point representation you expect
> as input (e.g. affine representation)?

I'll include documentation on the lines of ecdh.h for these functions in 
next patch series.

> Ciao
> Stephan
>

Regards,
- Nitin
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