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romulus/Romulus-M/romulus_m_reference.c

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/*
* Date: 05 May 2021
* Contact: Romulus Team (Mustafa Khairallah - mustafa.khairallah@ntu.edu.sg)
* Romulus-M as compliant with the Romulus v1.3 specifications.
* This file icludes the functions of Romulus-N
* It superseeds earlier versions developed by Mustafa Khairallah and maintained
* by Mustafa Khairallah, Thomas Peyrin and Kazuhiko Minematsu
*/
#include "api.h"
#include "variant.h"
#include "skinny.h"
#include "romulus_m.h"
// Padding function: pads the byte length of the message mod 16 to the last incomplete block.
// For complete blocks it returns the same block.
void pad (const unsigned char* m, unsigned char* mp, int l, int len8) {
int i;
for (i = 0; i < l; i++) {
if (i < len8) {
mp[i] = m[i];
}
else if (i == l - 1) {
mp[i] = (len8 & 0x0f);
}
else {
mp[i] = 0x00;
}
}
}
// G(S): generates the key stream from the internal state by multiplying the state S by the constant matrix G
void g8A (unsigned char* s, unsigned char* c) {
int i;
for (i = 0; i < 16; i++) {
c[i] = (s[i] >> 1) ^ (s[i] & 0x80) ^ ((s[i] & 0x01) << 7);
}
}
// Rho(S,A) pads an A block and XORs it to the internal state.
void rho_ad (const unsigned char* m,
unsigned char* s,
int len8,
int ver) {
int i;
unsigned char mp [16];
pad(m,mp,ver,len8);
for (i = 0; i < ver; i++) {
s[i] = s[i] ^ mp[i];
}
}
// Rho(S,M): pads an M block and outputs S'= M xor S and C = M xor G(S)
void rho (const unsigned char* m,
unsigned char* c,
unsigned char* s,
int len8,
int ver) {
int i;
unsigned char mp [16];
pad(m,mp,ver,len8);
g8A(s,c);
for (i = 0; i < ver; i++) {
s[i] = s[i] ^ mp[i];
if (i < len8) {
c[i] = c[i] ^ mp[i];
}
else {
c[i] = 0;
}
}
}
// Inverse-Rho(S,M): pads a C block and outputs S'= C xor G(S) xor S and M = C xor G(S)
void irho (unsigned char* m,
const unsigned char* c,
unsigned char* s,
int len8,
int ver) {
int i;
unsigned char cp [16];
pad(c,cp,ver,len8);
g8A(s,m);
for (i = 0; i < ver; i++) {
if (i < len8) {
s[i] = s[i] ^ cp[i] ^ m[i];
}
else {
s[i] = s[i] ^ cp[i];
}
if (i < len8) {
m[i] = m[i] ^ cp[i];
}
else {
m[i] = 0;
}
}
}
// Resets the value of the counter.
void reset_lfsr_gf56 (unsigned char* CNT) {
CNT[0] = 0x01;
CNT[1] = 0x00;
CNT[2] = 0x00;
CNT[3] = 0x00;
CNT[4] = 0x00;
CNT[5] = 0x00;
CNT[6] = 0x00;
}
// Applies CNT'=2 * CNT (mod GF(2^56)), where GF(2^56) is defined using the irreducible polynomial
// x^56 + x^7 + x^4 + x^2 + 1
void lfsr_gf56 (unsigned char* CNT) {
unsigned char fb0;
fb0 = CNT[6] >> 7;
CNT[6] = (CNT[6] << 1) | (CNT[5] >> 7);
CNT[5] = (CNT[5] << 1) | (CNT[4] >> 7);
CNT[4] = (CNT[4] << 1) | (CNT[3] >> 7);
CNT[3] = (CNT[3] << 1) | (CNT[2] >> 7);
CNT[2] = (CNT[2] << 1) | (CNT[1] >> 7);
CNT[1] = (CNT[1] << 1) | (CNT[0] >> 7);
if (fb0 == 1) {
CNT[0] = (CNT[0] << 1) ^ 0x95;
}
else {
CNT[0] = (CNT[0] << 1);
}
}
// Combines the secret key, nonce (or A block), counter and domain bits to form the full 384-bit tweakey
void compose_tweakey (unsigned char* KT,
const unsigned char* K,
unsigned char* T,
unsigned char* CNT,
unsigned char D,
int t) {
int i;
for (i = 0; i < 7; i++) {
KT[i] = CNT[i];
}
KT[i] = D;
for (i = 8; i < 16; i++) {
KT[i] = 0x00;
}
for (i = 0; i < t; i++) {
KT[i+16] = T[i];
}
for (i = 0; i < 16; i++) {
KT[i+16+t] = K[i];
}
}
// An interface between Romulus and the underlying TBC
void block_cipher(unsigned char* s,
const unsigned char* k, unsigned char* T,
unsigned char* CNT, unsigned char D, int t) {
unsigned char KT [48];
compose_tweakey(KT,k,T,CNT,D,t);
skinny_128_384_plus_enc (s,KT);
}
// Calls the TBC using the nonce as part of the tweakey
void nonce_encryption (const unsigned char* N,
unsigned char* CNT,
unsigned char*s, const unsigned char* k,
int t, unsigned char D) {
unsigned char T [16];
int i;
for (i = 0; i < t; i++) {
T[i] = N[i];
}
block_cipher(s,k,T,CNT,D,t);
}
// Generates the tag T from the final state S by applying T=G(S).
void generate_tag (unsigned char** c, unsigned char* s,
int n, unsigned long long* clen) {
g8A(s, *c);
*c = *c + n;
*c = *c - *clen;
}
// Absorbs and encrypts the message blocks.
unsigned long long msg_encryption (const unsigned char** M, unsigned char** c,
const unsigned char* N,
unsigned char* CNT,
unsigned char*s, const unsigned char* k,
unsigned int n, unsigned int t, unsigned char D,
unsigned long long mlen) {
int len8;
if (mlen >= n) {
len8 = n;
mlen = mlen - n;
}
else {
len8 = mlen;
mlen = 0;
}
rho(*M, *c, s, len8, n);
*c = *c + len8;
*M = *M + len8;
lfsr_gf56(CNT);
nonce_encryption(N,CNT,s,k,t,D);
return mlen;
}
// Absorbs and decrypts the ciphertext blocks.
unsigned long long msg_decryption (unsigned char** M, const unsigned char** c,
const unsigned char* N,
unsigned char* CNT,
unsigned char*s, const unsigned char* k,
unsigned int n, unsigned int t, unsigned char D,
unsigned long long clen) {
int len8;
if (clen >= n) {
len8 = n;
clen = clen - n;
}
else {
len8 = clen;
clen = 0;
}
irho(*M, *c, s, len8, n);
*c = *c + len8;
*M = *M + len8;
lfsr_gf56(CNT);
nonce_encryption(N,CNT,s,k,t,D);
return clen;
}
// Handles the special case when the number of blocks of A is odd
unsigned long long ad2msg_encryption (const unsigned char** M,
unsigned char* CNT,
unsigned char*s, const unsigned char* k,
unsigned int t, unsigned char D,
unsigned long long mlen) {
unsigned char T [16];
int len8;
if (mlen <= t) {
len8 = mlen;
mlen = 0;
}
else {
len8 = t;
mlen = mlen - t;
}
pad (*M,T,t,len8);
block_cipher(s,k,T,CNT,D,t);
lfsr_gf56(CNT);
*M = *M + len8;
return mlen;
}
// Absorbs the AD blocks.
unsigned long long ad_encryption (const unsigned char** A, unsigned char* s,
const unsigned char* k, unsigned long long adlen,
unsigned char* CNT,
unsigned char D,
unsigned int n, unsigned int t) {
unsigned char T [16];
int len8;
if (adlen >= n) {
len8 = n;
adlen = adlen - n;
}
else {
len8 = adlen;
adlen = 0;
}
rho_ad(*A, s, len8, n);
*A = *A + len8;
lfsr_gf56(CNT);
if (adlen != 0) {
if (adlen >= t) {
len8 = t;
adlen = adlen - t;
}
else {
len8 = adlen;
adlen = 0;
}
pad(*A, T, t, len8);
*A = *A + len8;
block_cipher(s,k,T,CNT,D,t);
lfsr_gf56(CNT);
}
return adlen;
}
int romulus_m_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
)
{
unsigned char s[16];
unsigned char CNT[7];
unsigned char T[16];
const unsigned char* N;
unsigned int n, t, i;
unsigned char w;
unsigned long long xlen;
(void)nsec;
N = npub;
n = AD_BLK_LEN_ODD;
t = AD_BLK_LEN_EVN;
xlen = mlen;
for (i = 0; i < n; i++) {
s[i] = 0;
}
reset_lfsr_gf56(CNT);
// Calculating the domain separation bits for the last block MAC TBC call depending on the length of M and AD
w = 48;
if (adlen == 0) {
w = w ^ 2;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < t) {
w = w ^ 1;
}
else if (xlen%(n+t) == t) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
else if (adlen%(n+t) == 0) {
w = w ^ 8;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < n) {
w = w ^ 1;
}
else if (xlen%(n+t) == n) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
else if (adlen%(n+t) < n) {
w = w ^ 2;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < t) {
w = w ^ 1;
}
else if (xlen%(n+t) == t) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
else if (adlen%(n+t) == n) {
w = w ^ 0;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < t) {
w = w ^ 1;
}
else if (xlen%(n+t) == t) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
else {
w = w ^ 10;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < n) {
w = w ^ 1;
}
else if (xlen%(n+t) == n) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
if (adlen == 0) { // AD is an empty string
lfsr_gf56(CNT);
}
else while (adlen > 0) {
adlen = ad_encryption(&ad,s,k,adlen,CNT,40,n,t);
}
if ((w & 8) == 0) {
xlen = ad2msg_encryption (&m,CNT,s,k,t,44,xlen);
}
else if (mlen == 0) {
lfsr_gf56(CNT);
}
while (xlen > 0) {
xlen = ad_encryption(&m,s,k,xlen,CNT,44,n,t);
}
nonce_encryption(N,CNT,s,k,t,w);
// Tag generation
g8A(s, T);
m = m - mlen;
reset_lfsr_gf56(CNT);
for (i = 0; i < n; i = i + 1) {
s[i] = T[i];
}
n = MSG_BLK_LEN;
*clen = mlen + n;
if (mlen > 0) {
nonce_encryption(N,CNT,s,k,t,36);
while (mlen > n) {
mlen = msg_encryption(&m,&c,N,CNT,s,k,n,t,36,mlen);
}
rho(m, c, s, mlen, 16);
c = c + mlen;
m = m + mlen;
}
// Tag Concatenation
for (i = 0; i < 16; i = i + 1) {
*(c + i) = T[i];
}
c = c - *clen;
return 0;
}
int romulus_m_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
)
{
unsigned char s[16];
unsigned char CNT[7];
unsigned char T[16];
const unsigned char* N;
unsigned int n, t, i;
unsigned char w;
unsigned long long xlen;
const unsigned char* mauth;
(void)nsec;
mauth = m;
N = npub;
n = AD_BLK_LEN_ODD;
t = AD_BLK_LEN_EVN;
xlen = clen-16;
reset_lfsr_gf56(CNT);
for (i = 0; i < 16; i++) {
T[i] = *(c + clen - 16 + i);
}
for (i = 0; i < n; i = i + 1) {
s[i] = T[i];
}
n = MSG_BLK_LEN;
clen = clen - 16;
*mlen = clen;
if (clen > 0) {
nonce_encryption(N,CNT,s,k,t,36);
while (clen > n) {
clen = msg_decryption(&m,&c,N,CNT,s,k,n,t,36,clen);
}
irho(m, c, s, clen, 16);
c = c + clen;
m = m + clen;
}
for (i = 0; i < n; i++) {
s[i] = 0;
}
reset_lfsr_gf56(CNT);
// Calculating the domain separation bits for the last block MAC TBC call depending on the length of M and AD
w = 48;
if (adlen == 0) {
w = w ^ 2;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < t) {
w = w ^ 1;
}
else if (xlen%(n+t) == t) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
else if (adlen%(n+t) == 0) {
w = w ^ 8;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < n) {
w = w ^ 1;
}
else if (xlen%(n+t) == n) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
else if (adlen%(n+t) < n) {
w = w ^ 2;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < t) {
w = w ^ 1;
}
else if (xlen%(n+t) == t) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
else if (adlen%(n+t) == n) {
w = w ^ 0;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < t) {
w = w ^ 1;
}
else if (xlen%(n+t) == t) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
else {
w = w ^ 10;
if (xlen == 0) {
w =w ^ 1;
}
else if (xlen%(n+t) == 0) {
w = w ^ 4;
}
else if (xlen%(n+t) < n) {
w = w ^ 1;
}
else if (xlen%(n+t) == n) {
w = w ^ 0;
}
else {
w = w ^ 5;
}
}
if (adlen == 0) { // AD is an empty string
lfsr_gf56(CNT);
}
else while (adlen > 0) {
adlen = ad_encryption(&ad,s,k,adlen,CNT,40,n,t);
}
if ((w & 8) == 0) {
xlen = ad2msg_encryption (&mauth,CNT,s,k,t,44,xlen);
}
else if (clen == 0) {
lfsr_gf56(CNT);
}
while (xlen > 0) {
xlen = ad_encryption(&mauth,s,k,xlen,CNT,44,n,t);
}
nonce_encryption(N,CNT,s,k,t,w);
// Tag generation
g8A(s, T);
// Tag verification
for (i = 0; i < 16; i++) {
if (T[i] != (*(c+i))) {
return -1;
}
}
return 0;
}
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