function checkPrime(prime, generator) {
var gen = generator.toString('hex');
var hex = [gen, prime.toString(16)].join('_');
if (hex in primeCache) {
return primeCache[hex];
}
var error = 0;
if (prime.isEven() ||
!primes.simpleSieve ||
!primes.fermatTest(prime) ||
!millerRabin.test(prime)) {
//not a prime so +1
error += 1;
if (gen === '02' || gen === '05') {
// we'd be able to check the generator
// it would fail so +8
error += 8;
} else {
//we wouldn't be able to test the generator
// so +4
error += 4;
}
primeCache[hex] = error;
return error;
}
if (!millerRabin.test(prime.shrn(1))) {
//not a safe prime
error += 2;
}
var rem;
switch (gen) {
case '02':
if (prime.mod(TWENTYFOUR).cmp(ELEVEN)) {
// unsuidable generator
error += 8;
}
break;
case '05':
rem = prime.mod(TEN);
if (rem.cmp(THREE) && rem.cmp(SEVEN)) {
// prime mod 10 needs to equal 3 or 7
error += 8;
}
break;
default:
error += 4;
}
primeCache[hex] = error;
return error;
}
function findPrime(bits, gen) {
if (bits < 16) {
// this is what openssl does
if (gen === 2 || gen === 5) {
return new BN([0x8c, 0x7b]);
} else {
return new BN([0x8c, 0x27]);
}
}
gen = new BN(gen);
var num, n2;
while (true) {
num = new BN(randomBytes(Math.ceil(bits / 8)));
while (num.bitLength() > bits) {
num.ishrn(1);
}
if (num.isEven()) {
num.iadd(ONE);
}
if (!num.testn(1)) {
num.iadd(TWO);
}
if (!gen.cmp(TWO)) {
while (num.mod(TWENTYFOUR).cmp(ELEVEN)) {
num.iadd(FOUR);
}
} else if (!gen.cmp(FIVE)) {
while (num.mod(TEN).cmp(THREE)) {
num.iadd(FOUR);
}
}
n2 = num.shrn(1);
if (simpleSieve(n2) && simpleSieve(num) &&
fermatTest(n2) && fermatTest(num) &&
millerRabin.test(n2) && millerRabin.test(num)) {
return num;
}
}
}
function findPrime(bits, gen) {
if (bits < 16) {
// this is what openssl does
if (gen === 2 || gen === 5) {
return new BN([0x8c, 0x7b]);
} else {
return new BN([0x8c, 0x27]);
}
}
gen = new BN(gen);
var runs, comp;
function generateRandom(bits) {
runs = -1;
var out = new BN(randomBytes(Math.ceil(bits / 8)));
while (out.bitLength() > bits) {
out.ishrn(1);
}
if (out.isEven()) {
out.iadd(ONE);
}
if (!out.testn(1)) {
out.iadd(TWO);
}
if (!gen.cmp(TWO)) {
while (out.mod(TWENTYFOUR).cmp(ELEVEN)) {
out.iadd(FOUR);
}
comp = {
major: [TWENTYFOUR],
minor: [TWELVE]
};
} else if (!gen.cmp(FIVE)) {
rem = out.mod(TEN);
while (rem.cmp(THREE)) {
out.iadd(FOUR);
rem = out.mod(TEN);
}
comp = {
major: [FOUR, SIXTEEN],
minor: [TWO, EIGHT]
};
} else {
comp = {
major: [FOUR],
minor: [TWO]
};
}
return out;
}
var num = generateRandom(bits);
var n2 = num.shrn(1);
while (true) {
while (num.bitLength() > bits) {
num = generateRandom(bits);
n2 = num.shrn(1);
}
runs++;
if (simpleSieve(n2) && simpleSieve(num) &&
fermatTest(n2) && fermatTest(num) &&
millerRabin.test(n2) && millerRabin.test(num)) {
return num;
}
num.iadd(comp.major[runs%comp.major.length]);
n2.iadd(comp.minor[runs%comp.minor.length]);
}
}