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use digest::{Digest, DynDigest, FixedOutputReset};
use num_bigint::traits::ModInverse;
use num_bigint::{BigUint, RandPrime};
#[allow(unused_imports)]
use num_traits::Float;
use num_traits::{FromPrimitive, One, Zero};
use rand_core::{CryptoRng, RngCore};
use crate::errors::{Error, Result};
use crate::key::RsaPrivateKey;
const EXP: u64 = 65537;
pub fn generate_multi_prime_key<R: RngCore + CryptoRng>(
rng: &mut R,
nprimes: usize,
bit_size: usize,
) -> Result<RsaPrivateKey> {
let exp = BigUint::from_u64(EXP).expect("invalid static exponent");
generate_multi_prime_key_with_exp(rng, nprimes, bit_size, &exp)
}
pub fn generate_multi_prime_key_with_exp<R: RngCore + CryptoRng>(
rng: &mut R,
nprimes: usize,
bit_size: usize,
exp: &BigUint,
) -> Result<RsaPrivateKey> {
if nprimes < 2 {
return Err(Error::NprimesTooSmall);
}
if bit_size < 64 {
let prime_limit = (1u64 << (bit_size / nprimes) as u64) as f64;
let mut pi = prime_limit / (prime_limit.ln() - 1f64);
pi /= 4f64;
pi /= 2f64;
if pi < nprimes as f64 {
return Err(Error::TooFewPrimes);
}
}
let mut primes = vec![BigUint::zero(); nprimes];
let n_final: BigUint;
let d_final: BigUint;
'next: loop {
let mut todo = bit_size;
if nprimes >= 7 {
todo += (nprimes - 2) / 5;
}
for (i, prime) in primes.iter_mut().enumerate() {
*prime = rng.gen_prime(todo / (nprimes - i));
todo -= prime.bits();
}
for (i, prime1) in primes.iter().enumerate() {
for prime2 in primes.iter().take(i) {
if prime1 == prime2 {
continue 'next;
}
}
}
let mut n = BigUint::one();
let mut totient = BigUint::one();
for prime in &primes {
n *= prime;
totient *= prime - BigUint::one();
}
if n.bits() != bit_size {
continue 'next;
}
if let Some(d) = exp.mod_inverse(totient) {
n_final = n;
d_final = d.to_biguint().unwrap();
break;
}
}
RsaPrivateKey::from_components(n_final, exp.clone(), d_final, primes)
}
pub fn mgf1_xor(out: &mut [u8], digest: &mut dyn DynDigest, seed: &[u8]) {
let mut counter = [0u8; 4];
let mut i = 0;
const MAX_LEN: u64 = core::u32::MAX as u64 + 1;
assert!(out.len() as u64 <= MAX_LEN);
while i < out.len() {
let mut digest_input = vec![0u8; seed.len() + 4];
digest_input[0..seed.len()].copy_from_slice(seed);
digest_input[seed.len()..].copy_from_slice(&counter);
digest.update(digest_input.as_slice());
let digest_output = &*digest.finalize_reset();
let mut j = 0;
loop {
if j >= digest_output.len() || i >= out.len() {
break;
}
out[i] ^= digest_output[j];
j += 1;
i += 1;
}
inc_counter(&mut counter);
}
}
pub fn mgf1_xor_digest<D>(out: &mut [u8], digest: &mut D, seed: &[u8])
where
D: Digest + FixedOutputReset,
{
let mut counter = [0u8; 4];
let mut i = 0;
const MAX_LEN: u64 = core::u32::MAX as u64 + 1;
assert!(out.len() as u64 <= MAX_LEN);
while i < out.len() {
Digest::update(digest, seed);
Digest::update(digest, counter);
let digest_output = digest.finalize_reset();
let mut j = 0;
loop {
if j >= digest_output.len() || i >= out.len() {
break;
}
out[i] ^= digest_output[j];
j += 1;
i += 1;
}
inc_counter(&mut counter);
}
}
fn inc_counter(counter: &mut [u8; 4]) {
for i in (0..4).rev() {
counter[i] = counter[i].wrapping_add(1);
if counter[i] != 0 {
return;
}
}
}