encrypt.c

#include "crypto_aead.h"

#include "siv.h"
#include "rijndael256.h"

#define AUTH_A_DOMAIN  0
#define AUTH_M_DOMAIN  1
#define AUTH_N_DOMAIN  3
#define ENC_M_DOMAIN   7

/* Declaration of basic internal functions */
static void Setup(const unsigned char *k);

static void AUTH(
	uint8_t *state_inout,
	const unsigned char *m, unsigned long long mlen,
	const unsigned char *ad, unsigned long long adlen,
	const unsigned char *npub);

static void ENC(
	uint8_t *state_inout,
	unsigned char *c,
	const unsigned char *m, unsigned long long mlen);

static void AUTH_AD(
	uint8_t *state_inout,
	uint8_t *next_domain,
	const unsigned char *ad, unsigned long long adlen);

static void AUTH_MsgNonce(
	uint8_t *state_inout,
	const unsigned char *m, unsigned long long mlen,
	const unsigned char *npub, uint8_t domain);

static void XOR_State(
	uint8_t *state_inout,
	const uint8_t *data_in,
	const size_t dlen_inbytes);


/* Definition of basic internal functions */
static void Setup(const unsigned char *k)
{
	rijndael256KeySched(k);
}

static void XOR_State(
	uint8_t *state_inout,
	const uint8_t *data_in,
	const size_t dlen_inbytes)
{
	size_t i;
	for (i = 0; i < dlen_inbytes; i++)
	{
		state_inout[i] ^= data_in[i];
	}
}

static void AUTH_AD(
	uint8_t *state_inout,
	uint8_t *next_domain,
	const unsigned char *ad, unsigned long long adlen)
{
	size_t i;

	i = adlen;
	while (i > STATE_INBYTES)
	{
		XOR_State(state_inout, ad, STATE_INBYTES);
		rijndael256Encrypt(state_inout, AUTH_A_DOMAIN);
		ad += STATE_INBYTES;
		i -= STATE_INBYTES;
	}
	XOR_State(state_inout, ad, i);
	
	if (i < STATE_INBYTES)
	{			
		state_inout[i] ^= 0x80; // State ^ padn(A[a])
		*next_domain = AUTH_M_DOMAIN;
	}
	else
	{
		*next_domain = AUTH_M_DOMAIN + 1;
	}
	rijndael256Encrypt(state_inout, AUTH_A_DOMAIN);	
}

static void AUTH_MsgNonce(
	uint8_t *state_inout,
	const unsigned char *m, unsigned long long mlen,
	const unsigned char *npub, uint8_t domain)
{
	size_t i;
	unsigned char auth_n_domain;

	i = mlen;
	while (i > STATE_INBYTES)
	{
		XOR_State(state_inout, m, STATE_INBYTES);
		rijndael256Encrypt(state_inout, domain);
		m += STATE_INBYTES;
		i -= STATE_INBYTES;
	}

	XOR_State(state_inout, m, i);
	if (i < (STATE_INBYTES - CRYPTO_NPUBBYTES))
	{
		state_inout[i] ^= 0x80; // State ^ pad(M[m])
		XOR_State(state_inout + (STATE_INBYTES - CRYPTO_NPUBBYTES), npub, CRYPTO_NPUBBYTES);
		auth_n_domain = AUTH_N_DOMAIN;
	}
	else if (i == (STATE_INBYTES - CRYPTO_NPUBBYTES))
	{
		XOR_State(state_inout + (STATE_INBYTES - CRYPTO_NPUBBYTES), npub, CRYPTO_NPUBBYTES);
		auth_n_domain = AUTH_N_DOMAIN + 1;
	}
	else if (i < STATE_INBYTES)
	{
		state_inout[i] ^= 0x80; // State ^ pad(M[m])
		rijndael256Encrypt(state_inout, domain);
		XOR_State(state_inout + (STATE_INBYTES - CRYPTO_NPUBBYTES), npub, CRYPTO_NPUBBYTES);
		auth_n_domain = AUTH_N_DOMAIN + 2;

	}
	else
	{
		rijndael256Encrypt(state_inout, domain);
		XOR_State(state_inout + (STATE_INBYTES - CRYPTO_NPUBBYTES), npub, CRYPTO_NPUBBYTES);
		auth_n_domain = AUTH_N_DOMAIN + 3;
	}
	rijndael256Encrypt(state_inout, auth_n_domain);	
}

static void AUTH(
	uint8_t *state_inout,
	const unsigned char *m, unsigned long long mlen,
	const unsigned char *ad, unsigned long long adlen,
	const unsigned char *npub)
{
	unsigned char auth_m_domain;

	memset(state_inout, 0, STATE_INBYTES);
	AUTH_AD(state_inout, &auth_m_domain, ad, adlen);
	AUTH_MsgNonce(state_inout, m, mlen, npub, auth_m_domain);
}

static void ENC(
	uint8_t *state_inout,
	unsigned char *c,
	const unsigned char *m, unsigned long long mlen)
{
	size_t i;
	i = mlen;
	while(i > STATE_INBYTES)
	{
		rijndael256Encrypt(state_inout, ENC_M_DOMAIN);
		memcpy(c, state_inout, STATE_INBYTES);
		XOR_State(c, m, STATE_INBYTES);
		i -= STATE_INBYTES;
		c += STATE_INBYTES;
		m += STATE_INBYTES;
	}
	rijndael256Encrypt(state_inout, ENC_M_DOMAIN);
	memcpy(c, state_inout, i);
	XOR_State(c, m, i);
}

int crypto_aead_encrypt(
	unsigned char *c, unsigned long long *clen,
	const unsigned char *m, unsigned long long mlen,
	const unsigned char *ad, unsigned long long adlen,
	const unsigned char *nsec,
	const unsigned char *npub,
	const unsigned char *k
	)
{
	/*
	... 
	... the code for the cipher implementation goes here,
	... generating a ciphertext c[0],c[1],...,c[*clen-1]
	... from a plaintext m[0],m[1],...,m[mlen-1]
	... and associated data ad[0],ad[1],...,ad[adlen-1]
	... and nonce npub[0],npub[1],..
	... and secret key k[0],k[1],...
	... the implementation shall not use nsec
	...
	... return 0;
	*/
	nsec = NULL;
	
	uint8_t state[STATE_INBYTES] = { 0 };

	Setup(k);
	AUTH(state, m, mlen, ad, adlen, npub);
	memcpy(c+mlen, state, TAG_INBYTES);
	ENC(state, c, m, mlen);

	*clen = mlen + TAG_INBYTES;
	return 0;
}

int crypto_aead_decrypt(
	unsigned char *m, unsigned long long *mlen,
	unsigned char *nsec,
	const unsigned char *c, unsigned long long clen,
	const unsigned char *ad, unsigned long long adlen,
	const unsigned char *npub,
	const unsigned char *k
	)
{
	/*
	...
	... the code for the AEAD implementation goes here,
	... generating a plaintext m[0],m[1],...,m[*mlen-1]
	... and secret message number nsec[0],nsec[1],...
	... from a ciphertext c[0],c[1],...,c[clen-1]
	... and associated data ad[0],ad[1],...,ad[adlen-1]
	... and nonce number npub[0],npub[1],...
	... and secret key k[0],k[1],...
	...
	... return 0;
	*/
	nsec = NULL;
	uint8_t state[STATE_INBYTES] = { 0 };
	uint64_t cmtlen;

	if (clen < TAG_INBYTES) return TAG_UNMATCH;
	cmtlen = clen - TAG_INBYTES;

	Setup(k);
	memcpy(state, c + cmtlen, TAG_INBYTES);
	ENC(state, m, c, cmtlen);
	AUTH(state, m, cmtlen, ad, adlen, npub);

	if (memcmp(state, c + cmtlen, TAG_INBYTES) != 0)
	{
		return TAG_UNMATCH;
	}

	*mlen = cmtlen;
	return TAG_MATCH;
}