Re: [PATCH 1/3] crypto: sm4 - create SM4 library based on sm4 generic code

[Eric Biggers <ebiggers@kernel.org>]

On Thu, Jun 10, 2021 at 09:44:57PM +0800, Tianjia Zhang wrote:
> Take the existing small footprint and mostly time invariant C code

It is using an S-box without any prefetching.  That doesn't look very
"time invariant" to me.

> diff --git a/lib/crypto/sm4.c b/lib/crypto/sm4.c
> new file mode 100644
> index 000000000000..cbdd14a254d0
[..]
> +/**
> + * crypto_sm4_expand_key - Expands the SM4 key as described in GB/T 32907-2016
> + * @ctx:	The location where the computed key will be stored.
> + * @in_key:	The supplied key.
> + * @key_len:	The length of the supplied key.
> + *
> + * Returns 0 on success. The function fails only if an invalid key size (or
> + * pointer) is supplied.
> + */
> +int crypto_sm4_expand_key(struct crypto_sm4_ctx *ctx, const u8 *in_key,
> +			  unsigned int key_len)
[...]
> +/**
> + * crypto_sm4_do_crypt - Encrypt or decrypt a single SM4 block
> + * @rk:		The rkey_enc for encrypt or rkey_dec for decrypt
> + * @out:	Buffer to store output data
> + * @in: 	Buffer containing the input data
> + */
> +void crypto_sm4_do_crypt(const u32 *rk, u8 *out, const u8 *in)

Calling these "sm4_expandkey()" and "sm4_crypt_block()" would be more consistent
with the other lib/crypto/ functions such as the AES ones.  The other
lib/crypto/ functions don't have a "crypto_" prefix, as that is used for
functions related to the traditional crypto API rather than the library API.

- Eric