48 lines
1.3 KiB
Rust
48 lines
1.3 KiB
Rust
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//! Generates [safe prime numbers](https://www.wikiwand.com/en/Sophie_Germain_prime).
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use ramp::Int;
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use rand::OsRng;
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pub use common::{gen_prime, is_prime};
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/// Constructs a new `SafePrime` with a size of `bit_length` bits.
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///
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/// This will initialize an `OsRng` instance and call the
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/// `SafePrime::from_rng()` method.
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///
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/// Note: the `bit_length` MUST be at least 512-bits.
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pub fn new(bit_length: usize) -> Int {
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debug_assert!(bit_length >= 512);
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let mut rngesus = match OsRng::new() {
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Ok(rng) => rng,
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Err(reason) => panic!("Error initializing RNG: {}", reason),
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};
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from_rng(bit_length, &mut rngesus)
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}
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/// Constructs a new `SafePrime` with the size of `bit_length` bits, sourced
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/// from an already-initialized `OsRng`.
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pub fn from_rng(bit_length: usize, mut rngesus: &mut OsRng) -> Int {
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debug_assert!(bit_length >= 512);
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let mut candidate: Int;
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// Circumvent uninitialized warning (technically valid but compiler
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// cannot determine that `clone_from` will fill the value.
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let mut candidate_p: Int = Int::zero();
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loop {
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candidate = gen_prime(bit_length, &mut rngesus);
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candidate_p.clone_from(&candidate);
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candidate_p -= 1_usize;
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candidate_p /= 2_usize;
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if is_prime(&candidate_p) {
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break;
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}
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}
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candidate
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}
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