#pragma once

#include "common.hpp"

// ISAP authenticated encryption with associated data ( AEAD )

namespace isap {

// Given 16 -bytes secret key, 16 -bytes public message nonce, N ( >=0 ) -bytes

// associated data, M ( >=0 ) -bytes plain text, this routine computes M -bytes

// cipher text along with 16 -bytes authentication tag, using any of

// these four algorithms {Isap-A-128a, Isap-A-128, Isap-K-128a, Isap-K-128}.

//

// Which specific algorithm from ISAP specification to be used, depends on

// choosen template parameters. See table 2.2 of ISAP specification

// https://csrc.nist.gov/CSRC/media/Projects/lightweight-cryptography/documents/finalist-round/updated-spec-doc/isap-spec-final.pdf

//

// Encryption algorithm follows generic pseudocode described in Algorithm 1, in

// above linked specification

template<const isap_common::perm_t p,

const size_t s_b,

const size_t s_k,

const size_t s_e,

const size_t s_h>

inline static void

encrypt(const uint8_t* const __restrict key,

const uint8_t* const __restrict nonce,

const uint8_t* const __restrict data,

const size_t dlen,

const uint8_t* const __restrict msg,

uint8_t* const __restrict cipher,

const size_t mlen,

uint8_t* const __restrict tag)

{

using namespace isap_common;

enc<p, s_b, s_k, s_e, s_h>(key, nonce, msg, cipher, mlen);

mac<p, s_b, s_k, s_e, s_h>(key, nonce, data, dlen, cipher, mlen, tag);

}

// Given 16 -bytes secret key, 16 -bytes public message nonce, 16 -bytes

// authentication tag, N ( >=0 ) -bytes associated data, M ( >=0 ) -bytes cipher

// text, this routine decrypts M -bytes plain text along with producing a

// boolean verification flag, using any of these four decryption algorithms

// {Isap-A-128a, Isap-A-128, Isap-K-128a, Isap-K-128}.

//

// Which specific algorithm from ISAP specification to be used, depends on

// choosen template parameters. See table 2.2 of ISAP specification

// https://csrc.nist.gov/CSRC/media/Projects/lightweight-cryptography/documents/finalist-round/updated-spec-doc/isap-spec-final.pdf

//

// Decryption algorithm follows generic pseudocode described in Algorithm 2, in

// above linked specification.

//

// Note, before consuming decrypted bytes, ensure that boolean verification flag

// holds truth value.

template<const isap_common::perm_t p,

const size_t s_b,

const size_t s_k,

const size_t s_e,

const size_t s_h>

inline static bool

decrypt(const uint8_t* const __restrict key,

const uint8_t* const __restrict nonce,

const uint8_t* const __restrict tag,

const uint8_t* const __restrict data,

const size_t dlen,

const uint8_t* const __restrict cipher,

uint8_t* const __restrict msg,

const size_t mlen)

{

using namespace isap_common;

uint8_t tag_[16];

mac<p, s_b, s_k, s_e, s_h>(key, nonce, data, dlen, cipher, mlen, tag_);

bool flg = false;

for (size_t i = 0; i < 16; i++) {

flg |= static_cast<bool>(tag[i] ^ tag_[i]);

}

if (flg) {

return !flg;

}

enc<p, s_b, s_k, s_e, s_h>(key, nonce, cipher, msg, mlen);

return !flg;

}

}