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#ifndef SPX_HASH_STATE_H
#define SPX_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.
*
* SHAKE256 does not need this state. Because this implementation is generated
* from a shared code base, we still need to specify some hash_state as it is
* still passed around. We chose to use an `int` as a placeholder for this
* purpose.
*/
#define hash_state int
#endif
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