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@deevashwer
deevashwer authored Jul 20, 2017
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310 changes: 310 additions & 0 deletions BGV.cpp
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#include "BGV_utils.h"

#define sigma 2400//8
#define mu 60
#define var 26

pari_sp ltop, lbot;

using namespace std;

class cryptosystem{
public:
int n, d, L, N;
GEN q, f, s, t, A, T, tensor_product_s;

cryptosystem(bool b, int l){
if(b == 0)
d = 1, n = 20;
else
n = 1, d = 20;
L = l;
f = cgetg(d + 2, t_VEC);
gel(f, 1) = gen_1;
gel(f, d + 1) = gen_1;
for(int i = 1; i < d; i++)
gel(f, i + 1) = gen_0;
f = gtopolyrev(f, -1);
N = 2*n*mu;
q = cgetg(L + 1, t_VEC);
s = cgetg(L + 1, t_VEC);
t = cgetg(L + 1, t_VEC);
A = cgetg(L + 1, t_VEC);
T = cgetg(L, t_VEC);
tensor_product_s = cgetg(L + 1, t_VEC);
for(int i = L; i > 0; i--){
gel(q, i) = gshift(gen_1, mu + var*i);
gel(q, i) = nextprime(gel(q, i));
generate_secret_key(i);
generate_public_key(i);
generate_tensor_products(i);
if(i != L)
switch_key_gen(i, (n + 1)*(n + 1), mu + (i + 1)*var);
}
}

GEN sample_error_polynomial(long variance, int j){
ltop = avma;
GEN tmp = Sample(d, variance);
tmp = gmodulo(tmp, gel(q, j));
//tmp = gmodulo(tmp, gel(q, L));
tmp = gtopolyrev(tmp, -1);
tmp = gmodulo(tmp, f);
//tmp = lift(lift(tmp));
lbot = avma;
tmp = gerepilecopy(ltop, tmp);
return tmp;
}

GEN sample_polynomial(int j){
ltop = avma;
GEN tmp = cgetg(d + 1, t_COL);
for(int i = 0; i < d; i++)
gel(tmp, i + 1) = generate_random(mu + var*j);
tmp = gmodulo(tmp, gel(q, j));
//tmp = gmodulo(tmp, gel(q, L));
tmp = gtopolyrev(tmp, -1);
tmp = gmodulo(tmp, f);
lbot = avma;
tmp = gerepilecopy(ltop, tmp);
return tmp;
}

void generate_secret_key(int j){
gel(s, j) = cgetg(n + 2, t_COL);
gel(gel(s, j), 1) = gen_1;
for(int i = 0; i < n; i++)
gel(gel(s, j), i + 2) = sample_error_polynomial(sigma, j);
gel(t, j) = cgetg(n + 1, t_COL);
for(int i = 0; i < n; i++)
gel(gel(t, j), i + 1) = gel(gel(s, j), i + 2);
//print(gel(s, j));
}

void generate_public_key(int j){
GEN B = cgetg(n + 1, t_MAT);
for(int i = 0; i < n; i++){
gel(B, i + 1) = cgetg(N + 1, t_COL);
for(int k = 0; k < N; k++){
//cout << i << " " << j << endl;
gel(gel(B, i + 1), k + 1) = sample_polynomial(j);
}
}
GEN e = cgetg(N + 1, t_COL);
for(int i = 0; i < N; i++)
gel(e, i + 1) = sample_error_polynomial(sigma, j);
e = gmul(gen_2, e);
GEN b = gmul(B, gel(t, j));
b = gadd(b, e);
gel(A, j) = cgetg(n + 2, t_MAT);
for(int i = 0; i < n + 1; i++)
gel(gel(A, j), i + 1) = cgetg(N + 1, t_COL);
for(int i = 0; i < N; i++)
gel(gel(gel(A, j), 1), i + 1) = gel(b, i + 1);
for(int i = 1; i < n + 1; i++)
gel(gel(A, j), i + 1) = gmul(gen_m1, gel(B, i));
}

void generate_tensor_products(int j){
gel(tensor_product_s, j) = cgetg((n + 1)*(n + 1) + 1, t_COL);
for(int i = 0; i < n + 1; i++)
for(int k = 0; k < n + 1; k++)
gel(gel(tensor_product_s, j), i*(n + 1) + k + 1) = gmul(gel(gel(s, j), i + 1), gel(gel(s, j), k + 1));
}

void switch_key_gen(int j, int n_1, int log_q){
gel(T, j) = cgetg(n + 2, t_MAT);
int N_custom = n_1*log_q;
GEN B = cgetg(n + 1, t_MAT);
for(int i = 0; i < n; i++){
gel(B, i + 1) = cgetg(N_custom + 1, t_COL);
for(int k = 0; k < N_custom; k++)
gel(gel(B, i + 1), k + 1) = sample_polynomial(j + 1);
}
GEN e = cgetg(N_custom + 1, t_COL);
for(int i = 0; i < N_custom; i++)
gel(e, i + 1) = sample_error_polynomial(sigma, j + 1);
e = gmul(gen_2, e);
GEN b = gmul(B, lift(lift(gel(t, j))));
b = gadd(b, e);
for(int i = 0; i < n + 1; i++)
gel(gel(T, j), i + 1) = cgetg(N_custom + 1, t_COL);
for(int i = 0; i < N_custom; i++)
gel(gel(gel(T, j), 1), i + 1) = gel(b, i + 1);
for(int i = 1; i < n + 1; i++)
gel(gel(T, j), i + 1) = gmul(gen_m1, gel(B, i));
//GEN test = gmul(gel(T, j), lift(lift(gel(s, j))));
//print(lift(lift(test)));
GEN tmp = PowersOf2(gel(tensor_product_s, j + 1), log_q, n_1);
//GEN tmp = PowersOf2(gel(s, j + 1), log_q, n_1);
//print(tmp);
gel(gel(T, j), 1) = gadd(gel(gel(T, j), 1), tmp);
return;
}

GEN switch_key(GEN ct_1, int j, int n_1, int log_q){
GEN ct_2 = gmul(shallowtrans(gel(T, j)), bit_decomposition(ct_1, log_q, n_1, d));
return ct_2;
}

GEN switch_moduli(GEN ct_1, int j){
GEN ct_2 = lift(lift(ct_1));
GEN tmp_1, tmp_2, tmp_3, tmp_4;
for(int i = 0; i < n + 1; i++){
tmp_1 = gtovecrev(gel(ct_2, i + 1));
for(int k = 0; k < d; k++){
gel(tmp_1, k + 1) = mulii(gel(tmp_1, k + 1), gel(q, j));
gel(tmp_1, k + 1) = diviiround(gel(tmp_1, k + 1), gel(q, j + 1));
}
gel(ct_2, i + 1) = gtopolyrev(tmp_1, -1);
}
for(int i = 0; i < n + 1; i++){
tmp_1 = gmod(gtovecrev(gel(ct_2, i + 1)), gel(q, j));
tmp_2 = gtovecrev(gel(lift(lift(ct_1)), i + 1));
tmp_4 = gmod(tmp_2, gen_2);
tmp_3 = gmod(tmp_1, gen_2);
for(int k = 0; k < d; k++)
if(mpcmp(gel(tmp_3, k + 1), gel(tmp_4, k + 1)) != 0)
gel(tmp_1, k + 1) = gadd(gel(tmp_1, k + 1), gen_1);
tmp_1 = gmodulo(tmp_1, gel(q, j));
tmp_1 = gtopolyrev(tmp_1, -1);
gel(ct_2, i + 1) = gmodulo(tmp_1, f);
}
return ct_2;
}

GEN encrypt(GEN m, int level){
ltop = avma;
GEN ct = cgetg(n + 2, t_COL);
gel(ct, 1) = m;
for(int i = 1; i < n + 1; i++)
gel(ct, i + 1) = gen_0;
GEN r = cgetg(N + 1, t_COL);
for(int i = 0; i < N; i++)
gel(r, i + 1) = sample_error_polynomial(1, level);
GEN tmp = gmul(shallowtrans(gel(A, level)), r);
ct = gadd(ct, tmp);
ct = gerepilecopy(ltop, ct);
return ct;
}

GEN decrypt(GEN ct, int level, bool show_error){
GEN m = cgetg(n + 2, t_COL);
m = gmul(shallowtrans(ct), lift(lift(gel(s, level))));
m = lift(lift(m));
m = gtovecrev(m);
for(int i = 0; i < d; i++){
//if(level < L && gcmp(gel(m, i + 1), gdiv(gel(q, level + 1), gen_2)) > 0)
// gel(m, i + 1) = gsub(gel(m, i + 1), gel(q, level + 1));
if(gcmp(gel(m, i + 1), gdiv(gel(q, level), gen_2)) > 0)
gel(m, i + 1) = gsub(gel(m, i + 1), gel(q, level));
if(!show_error)
gel(m, i + 1) = gmod(gel(m, i + 1), gen_2);
}
return m;
}

GEN addition(GEN ct_1, GEN ct_2){
GEN ct = gadd(ct_1, ct_2);
return ct;
}

GEN multiply(GEN ct_1, GEN ct_2){
GEN ct = cgetg((n + 1)*(n + 1) + 1, t_COL);
for(int i = 0; i < n + 1; i++)
for(int j = 0; j < n + 1; j++)
gel(ct, i*(n + 1) + j + 1) = gmul(gel(ct_1, i + 1), gel(ct_2, j + 1));
return ct;
}
};

class ciphertext{
public:
GEN value;
int level;
cryptosystem* pkc;

ciphertext(){};

ciphertext(cryptosystem* PKC){
pkc = PKC;
}

ciphertext(cryptosystem* PKC, GEN m){
level = PKC->L;
value = PKC->encrypt(m, level);
pkc = PKC;
}

ciphertext(cryptosystem* PKC, GEN m, int lev){
level = lev;
value = PKC->encrypt(m, level);
pkc = PKC;
}

GEN decrypt(){
return pkc->decrypt(value, level, false);
}

ciphertext operator+(const ciphertext& ct_2){
ciphertext result(pkc);
if(this->level == ct_2.level){
result.value = pkc->addition(this->value, ct_2.value);
result.level = this->level;
}
else
cout << "Error: The ciphertexts belong to different levels" << endl;
return result;
}

ciphertext operator*(const ciphertext& ct_2){
ciphertext result(pkc);
if(this->level == ct_2.level){
GEN temp = pkc->multiply(this->value, ct_2.value);
temp = pkc->switch_key(temp, this->level - 1, (pkc->n + 1)*(pkc->n + 1), mu + (this->level)*var);
result.value = pkc->switch_moduli(temp, this->level - 1);
result.level = this->level - 1;
}
else
cout << "Error: The ciphertexts belong to different levels" << endl;
return result;
}

void initialize(cryptosystem* PKC, GEN m){
level = PKC->L;
value = PKC->encrypt(m, level);
pkc = PKC;
}

void initialize(cryptosystem* PKC, GEN m, int lev){
level = lev;
value = PKC->encrypt(m, level);
pkc = PKC;
}

void custom_setup(GEN val, int lev, cryptosystem* PKC){
value = val;
level = lev;
pkc = PKC;
}

void print(){
cout << "Error (Level:" << level << "): " << GENtostr(pkc->decrypt(value, level, true)) << endl;
cout << "Plaintext: " << GENtostr(pkc->decrypt(value, level, false)) << endl;
}
};

int main(int argc, const char * argv[]) {
pari_init(20000000000, 2);
srand(time(NULL));
cryptosystem pkc(true, 10);
ciphertext ct[9];
ciphertext result(&pkc, gen_1);
for(int i = 0; i < 9; i++){
ct[i].initialize(&pkc, gen_1, 10 - i);
result = result * ct[i];
result.print();
}
pari_close();
return 0;
}
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