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pqcrypto/crypto_sign/sphincs-sha256-128s-robust/avx2/hash_state.h

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#ifndef PQCLEAN_SPHINCSSHA256128SROBUST_AVX2_HASH_STATE_H
#define PQCLEAN_SPHINCSSHA256128SROBUST_AVX2_HASH_STATE_H
/**
* Defines the type of the hash function state.
*
* Don't be fooled into thinking this instance of SPHINCS+ isn't stateless!
*
* From Section 7.2.2 from the SPHINCS+ round-2 specification:
*
* Each of the instances of the tweakable hash function take PK.seed as its
* first input, which is constant for a given key pair and, thus, across
* a single signature. This leads to a lot of redundant computation. To remedy
* this, we pad PK.seed to the length of a full 64-byte SHA-256 input block.
* Because of the Merkle-Damgård construction that underlies SHA-256, this
* allows for reuse of the intermediate SHA-256 state after the initial call to
* the compression function which improves performance.
*
* We pass this hash state around in functions, because otherwise we need to
* have a global variable.
*
* We use a struct to differentiate between the x1 and x8 variants of SHA256.
*/
#include "sha2.h"
#include "sha256avx.h"
typedef struct {
sha256ctx x1;
sha256ctxx8 x8;
} hash_state;
#endif