2024-03-12 18:39:48

by Stefan Berger

Subject: [PATCH v6 09/13] crypto: ecdsa - Replace ndigits with nbits where precision is needed

From: Stefan Berger <[email protected]>

Replace the usage of ndigits with nbits where more precise space
calculations are needed, such as in ecdsa_max_size where the length of a
coordinate is determined.

Signed-off-by: Stefan Berger <[email protected]>
Tested-by: Lukas Wunner <[email protected]>
---
crypto/ecdsa.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c
index 1814f009f971..4daefb40c37a 100644
--- a/crypto/ecdsa.c
+++ b/crypto/ecdsa.c
@@ -266,7 +266,7 @@ static unsigned int ecdsa_max_size(struct crypto_akcipher *tfm)
{
struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);

- return ctx->pub_key.ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
+ return DIV_ROUND_UP(ctx->curve->nbits, 8);
}

static int ecdsa_nist_p384_init_tfm(struct crypto_akcipher *tfm)
--
2.43.0

2024-03-18 21:06:32

by Jarkko Sakkinen

Subject: Re: [PATCH v6 09/13] crypto: ecdsa - Replace ndigits with nbits where precision is needed

On Tue Mar 12, 2024 at 8:36 PM EET, Stefan Berger wrote:
> From: Stefan Berger <[email protected]>
>
> Replace the usage of ndigits with nbits where more precise space
> calculations are needed, such as in ecdsa_max_size where the length of a
> coordinate is determined.

What does "more precise" mean?

>
> Signed-off-by: Stefan Berger <[email protected]>
> Tested-by: Lukas Wunner <[email protected]>
> ---
> crypto/ecdsa.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c
> index 1814f009f971..4daefb40c37a 100644
> --- a/crypto/ecdsa.c
> +++ b/crypto/ecdsa.c
> @@ -266,7 +266,7 @@ static unsigned int ecdsa_max_size(struct crypto_akcipher *tfm)
> {
> struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
>
> - return ctx->pub_key.ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
> + return DIV_ROUND_UP(ctx->curve->nbits, 8);
> }
>
> static int ecdsa_nist_p384_init_tfm(struct crypto_akcipher *tfm)

BR, Jarkko