diff mbox series

[v6,06/13] crypto: ecc - Implement vli_mmod_fast_521 for NIST p521

Message ID 20240312183618.1211745-7-stefanb@linux.vnet.ibm.com (mailing list archive)
State Superseded
Delegated to: Herbert Xu
Headers show
Series Add support for NIST P521 to ecdsa | expand

Commit Message

Stefan Berger March 12, 2024, 6:36 p.m. UTC 
From: Stefan Berger <stefanb@linux.ibm.com>

Implement vli_mmod_fast_521 following the description for how to calculate
the modulus for NIST P521 in the NIST publication "Recommendations for
Discrete Logarithm-Based Cryptography: Elliptic Curve Domain Parameters"
section G.1.4.

NIST p521 requires 9 64bit digits, so increase the ECC_MAX_DIGITS so that
arrays fit the larger numbers.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 crypto/ecc.c                  | 25 +++++++++++++++++++++++++
 include/crypto/internal/ecc.h |  3 ++-
 2 files changed, 27 insertions(+), 1 deletion(-)

Comments

Bharat Bhushan March 18, 2024, 5:47 a.m. UTC | #1 
> -----Original Message-----
> From: Stefan Berger <stefanb@linux.vnet.ibm.com>
> Sent: Wednesday, March 13, 2024 12:06 AM
> To: keyrings@vger.kernel.org; linux-crypto@vger.kernel.org;
> herbert@gondor.apana.org.au; davem@davemloft.net
> Cc: linux-kernel@vger.kernel.org; saulo.alessandre@tse.jus.br;
> lukas@wunner.de; Bharat Bhushan <bbhushan2@marvell.com>;
> jarkko@kernel.org; Stefan Berger <stefanb@linux.ibm.com>
> Subject: [EXTERNAL] [PATCH v6 06/13] crypto: ecc - Implement
> vli_mmod_fast_521 for NIST p521
> 
> Prioritize security for external emails: Confirm sender and content safety
> before clicking links or opening attachments
> 
> ----------------------------------------------------------------------
> From: Stefan Berger <stefanb@linux.ibm.com>
> 
> Implement vli_mmod_fast_521 following the description for how to calculate
> the modulus for NIST P521 in the NIST publication "Recommendations for
> Discrete Logarithm-Based Cryptography: Elliptic Curve Domain Parameters"
> section G.1.4.
> 
> NIST p521 requires 9 64bit digits, so increase the ECC_MAX_DIGITS so that
> arrays fit the larger numbers.
> 
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>  crypto/ecc.c                  | 25 +++++++++++++++++++++++++
>  include/crypto/internal/ecc.h |  3 ++-
>  2 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/crypto/ecc.c b/crypto/ecc.c index 415a2f4e7291..99d41887c005
> 100644
> --- a/crypto/ecc.c
> +++ b/crypto/ecc.c
> @@ -902,6 +902,28 @@ static void vli_mmod_fast_384(u64 *result, const
> u64 *product,  #undef AND64H  #undef AND64L
> 
> +/*
> + * Computes result = product % curve_prime
> + * from "Recommendations for Discrete Logarithm-Based Cryptography:
> + *       Elliptic Curve Domain Parameters" section G.1.4
> + */
> +static void vli_mmod_fast_521(u64 *result, const u64 *product,
> +			      const u64 *curve_prime, u64 *tmp) {
> +	const unsigned int ndigits = ECC_CURVE_NIST_P521_DIGITS;
> +	size_t i;
> +
> +	/* Initialize result with lowest 521 bits from product */
> +	vli_set(result, product, ndigits);
> +	result[8] &= 0x1ff;
> +
> +	for (i = 0; i < ndigits; i++)
> +		tmp[i] = (product[8 + i] >> 9) | (product[9 + i] << 55);
> +	tmp[8] &= 0x1ff;

Can we get away from this hardcoding, like 9, 55, 0x1ff etc.
Or at least add comment about these.

> +
> +	vli_mod_add(result, result, tmp, curve_prime, ndigits); }
> +
>  /* Computes result = product % curve_prime for different curve_primes.
>   *
>   * Note that curve_primes are distinguished just by heuristic check and @@ -
> 941,6 +963,9 @@ static bool vli_mmod_fast(u64 *result, u64 *product,
>  	case ECC_CURVE_NIST_P384_DIGITS:
>  		vli_mmod_fast_384(result, product, curve_prime, tmp);
>  		break;
> +	case ECC_CURVE_NIST_P521_DIGITS:
> +		vli_mmod_fast_521(result, product, curve_prime, tmp);
> +		break;
>  	default:
>  		pr_err_ratelimited("ecc: unsupported digits size!\n");
>  		return false;
> diff --git a/include/crypto/internal/ecc.h b/include/crypto/internal/ecc.h index
> ab722a8986b7..4e2f5f938e91 100644
> --- a/include/crypto/internal/ecc.h
> +++ b/include/crypto/internal/ecc.h
> @@ -33,7 +33,8 @@
>  #define ECC_CURVE_NIST_P192_DIGITS  3
>  #define ECC_CURVE_NIST_P256_DIGITS  4
>  #define ECC_CURVE_NIST_P384_DIGITS  6
> -#define ECC_MAX_DIGITS              (512 / 64) /* due to ecrdsa */
> +#define ECC_CURVE_NIST_P521_DIGITS  9

Maybe these can be defined as:
#define ECC_CURVE_NIST_P521_DIGITS  (DIV_ROUND_UP(521, 64) /* NIST P521 */)

> +#define ECC_MAX_DIGITS              DIV_ROUND_UP(521, 64) /* NIST P521 */

/* NIST_P521 is max digits */
#define ECC_MAX_DIGITS              ECC_CURVE_ _DIGITS

Thanks
-Bharat

> 
>  #define ECC_DIGITS_TO_BYTES_SHIFT 3
> 
> --
> 2.43.0
Stefan Berger March 18, 2024, 6:38 p.m. UTC | #2 
On 3/18/24 01:47, Bharat Bhushan wrote:
> 
> 
>> -----Original Message-----
>> From: Stefan Berger <stefanb@linux.vnet.ibm.com>
>> Sent: Wednesday, March 13, 2024 12:06 AM
>> To: keyrings@vger.kernel.org; linux-crypto@vger.kernel.org;
>> herbert@gondor.apana.org.au; davem@davemloft.net
>> Cc: linux-kernel@vger.kernel.org; saulo.alessandre@tse.jus.br;
>> lukas@wunner.de; Bharat Bhushan <bbhushan2@marvell.com>;
>> jarkko@kernel.org; Stefan Berger <stefanb@linux.ibm.com>
>> Subject: [EXTERNAL] [PATCH v6 06/13] crypto: ecc - Implement
>> vli_mmod_fast_521 for NIST p521
>>
>> Prioritize security for external emails: Confirm sender and content safety
>> before clicking links or opening attachments
>>
>> ----------------------------------------------------------------------
>> From: Stefan Berger <stefanb@linux.ibm.com>
>>
>> Implement vli_mmod_fast_521 following the description for how to calculate
>> the modulus for NIST P521 in the NIST publication "Recommendations for
>> Discrete Logarithm-Based Cryptography: Elliptic Curve Domain Parameters"
>> section G.1.4.
>>
>> NIST p521 requires 9 64bit digits, so increase the ECC_MAX_DIGITS so that
>> arrays fit the larger numbers.
>>
>> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
>> ---
>>   crypto/ecc.c                  | 25 +++++++++++++++++++++++++
>>   include/crypto/internal/ecc.h |  3 ++-
>>   2 files changed, 27 insertions(+), 1 deletion(-)
>>
>> diff --git a/crypto/ecc.c b/crypto/ecc.c index 415a2f4e7291..99d41887c005
>> 100644
>> --- a/crypto/ecc.c
>> +++ b/crypto/ecc.c
>> @@ -902,6 +902,28 @@ static void vli_mmod_fast_384(u64 *result, const
>> u64 *product,  #undef AND64H  #undef AND64L
>>
>> +/*
>> + * Computes result = product % curve_prime
>> + * from "Recommendations for Discrete Logarithm-Based Cryptography:
>> + *       Elliptic Curve Domain Parameters" section G.1.4
>> + */
>> +static void vli_mmod_fast_521(u64 *result, const u64 *product,
>> +			      const u64 *curve_prime, u64 *tmp) {
>> +	const unsigned int ndigits = ECC_CURVE_NIST_P521_DIGITS;
>> +	size_t i;
>> +
>> +	/* Initialize result with lowest 521 bits from product */
>> +	vli_set(result, product, ndigits);
>> +	result[8] &= 0x1ff;
>> +
>> +	for (i = 0; i < ndigits; i++)
>> +		tmp[i] = (product[8 + i] >> 9) | (product[9 + i] << 55);
>> +	tmp[8] &= 0x1ff;
> 
> Can we get away from this hardcoding, like 9, 55, 0x1ff etc.
> Or at least add comment about these.
> 
>> +
>> +	vli_mod_add(result, result, tmp, curve_prime, ndigits); }
>> +
>>   /* Computes result = product % curve_prime for different curve_primes.
>>    *
>>    * Note that curve_primes are distinguished just by heuristic check and @@ -
>> 941,6 +963,9 @@ static bool vli_mmod_fast(u64 *result, u64 *product,
>>   	case ECC_CURVE_NIST_P384_DIGITS:
>>   		vli_mmod_fast_384(result, product, curve_prime, tmp);
>>   		break;
>> +	case ECC_CURVE_NIST_P521_DIGITS:
>> +		vli_mmod_fast_521(result, product, curve_prime, tmp);
>> +		break;
>>   	default:
>>   		pr_err_ratelimited("ecc: unsupported digits size!\n");
>>   		return false;
>> diff --git a/include/crypto/internal/ecc.h b/include/crypto/internal/ecc.h index
>> ab722a8986b7..4e2f5f938e91 100644
>> --- a/include/crypto/internal/ecc.h
>> +++ b/include/crypto/internal/ecc.h
>> @@ -33,7 +33,8 @@
>>   #define ECC_CURVE_NIST_P192_DIGITS  3
>>   #define ECC_CURVE_NIST_P256_DIGITS  4
>>   #define ECC_CURVE_NIST_P384_DIGITS  6
>> -#define ECC_MAX_DIGITS              (512 / 64) /* due to ecrdsa */
>> +#define ECC_CURVE_NIST_P521_DIGITS  9
> 
> Maybe these can be defined as:
> #define ECC_CURVE_NIST_P521_DIGITS  (DIV_ROUND_UP(521, 64) /* NIST P521 */)

I think for NIST P521 9 can be pre-calculated. It will not change 
anymore in the future.

> 
>> +#define ECC_MAX_DIGITS              DIV_ROUND_UP(521, 64) /* NIST P521 */
> 
> /* NIST_P521 is max digits */
> #define ECC_MAX_DIGITS              ECC_CURVE_ _DIGITS

In this case I think the DIV_ROUND_UP() along with the comment shows 
that it needs to be updated if ever a larger curve comes along.

> 
> Thanks
> -Bharat
> 
>>
>>   #define ECC_DIGITS_TO_BYTES_SHIFT 3
>>
>> --
>> 2.43.0
>
Jarkko Sakkinen March 18, 2024, 8:35 p.m. UTC | #3 
On Tue Mar 12, 2024 at 8:36 PM EET, Stefan Berger wrote:
> From: Stefan Berger <stefanb@linux.ibm.com>
>
> Implement vli_mmod_fast_521 following the description for how to calculate
> the modulus for NIST P521 in the NIST publication "Recommendations for
> Discrete Logarithm-Based Cryptography: Elliptic Curve Domain Parameters"
> section G.1.4.
>
> NIST p521 requires 9 64bit digits, so increase the ECC_MAX_DIGITS so that
> arrays fit the larger numbers.
>
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

Should provide context on what it will be used (for completeness).


> ---
>  crypto/ecc.c                  | 25 +++++++++++++++++++++++++
>  include/crypto/internal/ecc.h |  3 ++-
>  2 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/crypto/ecc.c b/crypto/ecc.c
> index 415a2f4e7291..99d41887c005 100644
> --- a/crypto/ecc.c
> +++ b/crypto/ecc.c
> @@ -902,6 +902,28 @@ static void vli_mmod_fast_384(u64 *result, const u64 *product,
>  #undef AND64H
>  #undef AND64L
>  
> +/*
> + * Computes result = product % curve_prime
> + * from "Recommendations for Discrete Logarithm-Based Cryptography:
> + *       Elliptic Curve Domain Parameters" section G.1.4
> + */
> +static void vli_mmod_fast_521(u64 *result, const u64 *product,
> +			      const u64 *curve_prime, u64 *tmp)
> +{
> +	const unsigned int ndigits = ECC_CURVE_NIST_P521_DIGITS;
> +	size_t i;
> +
> +	/* Initialize result with lowest 521 bits from product */
> +	vli_set(result, product, ndigits);
> +	result[8] &= 0x1ff;
> +
> +	for (i = 0; i < ndigits; i++)
> +		tmp[i] = (product[8 + i] >> 9) | (product[9 + i] << 55);
> +	tmp[8] &= 0x1ff;
> +
> +	vli_mod_add(result, result, tmp, curve_prime, ndigits);
> +}
> +
>  /* Computes result = product % curve_prime for different curve_primes.
>   *
>   * Note that curve_primes are distinguished just by heuristic check and
> @@ -941,6 +963,9 @@ static bool vli_mmod_fast(u64 *result, u64 *product,
>  	case ECC_CURVE_NIST_P384_DIGITS:
>  		vli_mmod_fast_384(result, product, curve_prime, tmp);
>  		break;
> +	case ECC_CURVE_NIST_P521_DIGITS:
> +		vli_mmod_fast_521(result, product, curve_prime, tmp);
> +		break;
>  	default:
>  		pr_err_ratelimited("ecc: unsupported digits size!\n");
>  		return false;
> diff --git a/include/crypto/internal/ecc.h b/include/crypto/internal/ecc.h
> index ab722a8986b7..4e2f5f938e91 100644
> --- a/include/crypto/internal/ecc.h
> +++ b/include/crypto/internal/ecc.h
> @@ -33,7 +33,8 @@
>  #define ECC_CURVE_NIST_P192_DIGITS  3
>  #define ECC_CURVE_NIST_P256_DIGITS  4
>  #define ECC_CURVE_NIST_P384_DIGITS  6
> -#define ECC_MAX_DIGITS              (512 / 64) /* due to ecrdsa */
> +#define ECC_CURVE_NIST_P521_DIGITS  9
> +#define ECC_MAX_DIGITS              DIV_ROUND_UP(521, 64) /* NIST P521 */
>  
>  #define ECC_DIGITS_TO_BYTES_SHIFT 3
>  

Otherwise, lgtm

BR, Jarkko
Bharat Bhushan March 19, 2024, 3:53 a.m. UTC | #4 
> -----Original Message-----
> From: Stefan Berger <stefanb@linux.ibm.com>
> Sent: Tuesday, March 19, 2024 12:09 AM
> To: Bharat Bhushan <bbhushan2@marvell.com>; Stefan Berger
> <stefanb@linux.vnet.ibm.com>; keyrings@vger.kernel.org; linux-
> crypto@vger.kernel.org; herbert@gondor.apana.org.au;
> davem@davemloft.net
> Cc: linux-kernel@vger.kernel.org; saulo.alessandre@tse.jus.br;
> lukas@wunner.de; jarkko@kernel.org
> Subject: [EXTERNAL] Re: [PATCH v6 06/13] crypto: ecc - Implement
> vli_mmod_fast_521 for NIST p521
> 
> ----------------------------------------------------------------------
> 
> 
> On 3/18/24 01:47, Bharat Bhushan wrote:
> >
> >
> >> -----Original Message-----
> >> From: Stefan Berger <stefanb@linux.vnet.ibm.com>
> >> Sent: Wednesday, March 13, 2024 12:06 AM
> >> To: keyrings@vger.kernel.org; linux-crypto@vger.kernel.org;
> >> herbert@gondor.apana.org.au; davem@davemloft.net
> >> Cc: linux-kernel@vger.kernel.org; saulo.alessandre@tse.jus.br;
> >> lukas@wunner.de; Bharat Bhushan <bbhushan2@marvell.com>;
> >> jarkko@kernel.org; Stefan Berger <stefanb@linux.ibm.com>
> >> Subject: [EXTERNAL] [PATCH v6 06/13] crypto: ecc - Implement
> >> vli_mmod_fast_521 for NIST p521
> >>
> >> ---------------------------------------------------------------------
> >> -
> >> From: Stefan Berger <stefanb@linux.ibm.com>
> >>
> >> Implement vli_mmod_fast_521 following the description for how to
> >> calculate the modulus for NIST P521 in the NIST publication
> >> "Recommendations for Discrete Logarithm-Based Cryptography: Elliptic
> Curve Domain Parameters"
> >> section G.1.4.
> >>
> >> NIST p521 requires 9 64bit digits, so increase the ECC_MAX_DIGITS so
> >> that arrays fit the larger numbers.
> >>
> >> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> >> ---
> >>   crypto/ecc.c                  | 25 +++++++++++++++++++++++++
> >>   include/crypto/internal/ecc.h |  3 ++-
> >>   2 files changed, 27 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/crypto/ecc.c b/crypto/ecc.c index
> >> 415a2f4e7291..99d41887c005
> >> 100644
> >> --- a/crypto/ecc.c
> >> +++ b/crypto/ecc.c
> >> @@ -902,6 +902,28 @@ static void vli_mmod_fast_384(u64 *result, const
> >> u64 *product,  #undef AND64H  #undef AND64L
> >>
> >> +/*
> >> + * Computes result = product % curve_prime
> >> + * from "Recommendations for Discrete Logarithm-Based Cryptography:
> >> + *       Elliptic Curve Domain Parameters" section G.1.4
> >> + */
> >> +static void vli_mmod_fast_521(u64 *result, const u64 *product,
> >> +			      const u64 *curve_prime, u64 *tmp) {
> >> +	const unsigned int ndigits = ECC_CURVE_NIST_P521_DIGITS;
> >> +	size_t i;
> >> +
> >> +	/* Initialize result with lowest 521 bits from product */
> >> +	vli_set(result, product, ndigits);
> >> +	result[8] &= 0x1ff;
> >> +
> >> +	for (i = 0; i < ndigits; i++)
> >> +		tmp[i] = (product[8 + i] >> 9) | (product[9 + i] << 55);
> >> +	tmp[8] &= 0x1ff;
> >
> > Can we get away from this hardcoding, like 9, 55, 0x1ff etc.
> > Or at least add comment about these.
> >
> >> +
> >> +	vli_mod_add(result, result, tmp, curve_prime, ndigits); }
> >> +
> >>   /* Computes result = product % curve_prime for different curve_primes.
> >>    *
> >>    * Note that curve_primes are distinguished just by heuristic check
> >> and @@ -
> >> 941,6 +963,9 @@ static bool vli_mmod_fast(u64 *result, u64 *product,
> >>   	case ECC_CURVE_NIST_P384_DIGITS:
> >>   		vli_mmod_fast_384(result, product, curve_prime, tmp);
> >>   		break;
> >> +	case ECC_CURVE_NIST_P521_DIGITS:
> >> +		vli_mmod_fast_521(result, product, curve_prime, tmp);
> >> +		break;
> >>   	default:
> >>   		pr_err_ratelimited("ecc: unsupported digits size!\n");
> >>   		return false;
> >> diff --git a/include/crypto/internal/ecc.h
> >> b/include/crypto/internal/ecc.h index
> >> ab722a8986b7..4e2f5f938e91 100644
> >> --- a/include/crypto/internal/ecc.h
> >> +++ b/include/crypto/internal/ecc.h
> >> @@ -33,7 +33,8 @@
> >>   #define ECC_CURVE_NIST_P192_DIGITS  3
> >>   #define ECC_CURVE_NIST_P256_DIGITS  4
> >>   #define ECC_CURVE_NIST_P384_DIGITS  6
> >> -#define ECC_MAX_DIGITS              (512 / 64) /* due to ecrdsa */
> >> +#define ECC_CURVE_NIST_P521_DIGITS  9
> >
> > Maybe these can be defined as:
> > #define ECC_CURVE_NIST_P521_DIGITS  (DIV_ROUND_UP(521, 64) /* NIST
> > P521 */)
> 
> I think for NIST P521 9 can be pre-calculated. It will not change anymore in the
> future.

pre-calculation for others is perfect division by 64 but not for P521. So that creates a little confusion why it is 9 and not 8.
So in my view we can either use same logic used for ECC_MAX_DIGITS or a comment that it is rounded up. Anyways not a major concern.

Thanks
-Bharat

> 
> >
> >> +#define ECC_MAX_DIGITS              DIV_ROUND_UP(521, 64) /* NIST P521
> */
> >
> > /* NIST_P521 is max digits */
> > #define ECC_MAX_DIGITS              ECC_CURVE_ _DIGITS
> 
> In this case I think the DIV_ROUND_UP() along with the comment shows that
> it needs to be updated if ever a larger curve comes along.
> 
> >
> > Thanks
> > -Bharat
> >
> >>
> >>   #define ECC_DIGITS_TO_BYTES_SHIFT 3
> >>
> >> --
> >> 2.43.0
> >
diff mbox series

Patch

diff --git a/crypto/ecc.c b/crypto/ecc.c
index 415a2f4e7291..99d41887c005 100644
--- a/crypto/ecc.c
+++ b/crypto/ecc.c
@@ -902,6 +902,28 @@  static void vli_mmod_fast_384(u64 *result, const u64 *product,
 #undef AND64H
 #undef AND64L
 
+/*
+ * Computes result = product % curve_prime
+ * from "Recommendations for Discrete Logarithm-Based Cryptography:
+ *       Elliptic Curve Domain Parameters" section G.1.4
+ */
+static void vli_mmod_fast_521(u64 *result, const u64 *product,
+			      const u64 *curve_prime, u64 *tmp)
+{
+	const unsigned int ndigits = ECC_CURVE_NIST_P521_DIGITS;
+	size_t i;
+
+	/* Initialize result with lowest 521 bits from product */
+	vli_set(result, product, ndigits);
+	result[8] &= 0x1ff;
+
+	for (i = 0; i < ndigits; i++)
+		tmp[i] = (product[8 + i] >> 9) | (product[9 + i] << 55);
+	tmp[8] &= 0x1ff;
+
+	vli_mod_add(result, result, tmp, curve_prime, ndigits);
+}
+
 /* Computes result = product % curve_prime for different curve_primes.
  *
  * Note that curve_primes are distinguished just by heuristic check and
@@ -941,6 +963,9 @@  static bool vli_mmod_fast(u64 *result, u64 *product,
 	case ECC_CURVE_NIST_P384_DIGITS:
 		vli_mmod_fast_384(result, product, curve_prime, tmp);
 		break;
+	case ECC_CURVE_NIST_P521_DIGITS:
+		vli_mmod_fast_521(result, product, curve_prime, tmp);
+		break;
 	default:
 		pr_err_ratelimited("ecc: unsupported digits size!\n");
 		return false;
diff --git a/include/crypto/internal/ecc.h b/include/crypto/internal/ecc.h
index ab722a8986b7..4e2f5f938e91 100644
--- a/include/crypto/internal/ecc.h
+++ b/include/crypto/internal/ecc.h
@@ -33,7 +33,8 @@ 
 #define ECC_CURVE_NIST_P192_DIGITS  3
 #define ECC_CURVE_NIST_P256_DIGITS  4
 #define ECC_CURVE_NIST_P384_DIGITS  6
-#define ECC_MAX_DIGITS              (512 / 64) /* due to ecrdsa */
+#define ECC_CURVE_NIST_P521_DIGITS  9
+#define ECC_MAX_DIGITS              DIV_ROUND_UP(521, 64) /* NIST P521 */
 
 #define ECC_DIGITS_TO_BYTES_SHIFT 3