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extern crate curve25519_dalek; extern crate digest; extern crate generic_array; extern crate rand_core; #[macro_use(shuffle)] extern crate packed_simd; extern crate aes_ctr; extern crate byteorder; extern crate rand; #[cfg(test)] extern crate sha3; use rand_core::{CryptoRng, RngCore}; use curve25519_dalek::constants; use curve25519_dalek::ristretto::CompressedRistretto; use curve25519_dalek::ristretto::RistrettoPoint; use curve25519_dalek::scalar::Scalar; use digest::Digest; use generic_array::GenericArray; pub mod ecc; pub mod extension; pub struct Sender { s_bytes: [u8; 32], t: RistrettoPoint, y: Scalar, } impl Sender { pub fn new<R>(csprng: &mut R) -> (Self, [u8; 32]) where R: CryptoRng + RngCore, { let y = Scalar::random(csprng); let s = &y * &constants::RISTRETTO_BASEPOINT_TABLE; let t = &y * &s; let s_bytes = *s.compress().as_bytes(); let sender = Sender { s_bytes, t, y }; (sender, s_bytes) } pub fn keys<D>(&self, r_bytes: &[u8], n: usize) -> Option<Vec<GenericArray<u8, D::OutputSize>>> where D: Digest + Default, { let r = CompressedRistretto::from_slice(r_bytes).decompress()?; let mut secrets = Vec::new(); let mut secret = self.y * r; for _ in 1..n { secrets.push(secret.compress()); secret -= self.t; } secrets.push(secret.compress()); let mut hash = D::default(); let mut keys = Vec::new(); for secret in secrets.iter() { hash.input(self.s_bytes); hash.input(r_bytes); hash.input(secret.as_bytes()); keys.push(hash.result_reset()); } Some(keys) } } pub struct Receiver { x: Scalar, s: RistrettoPoint, s_bytes: [u8; 32], r_bytes: [u8; 32], } impl Receiver { pub fn new<R>(csprng: &mut R, choice: usize, s_bytes: &[u8; 32]) -> Option<(Self, [u8; 32])> where R: RngCore + CryptoRng, { let s = CompressedRistretto::from_slice(s_bytes).decompress()?; let choice = Scalar::from(choice as u64); let x = Scalar::random(csprng); let r = &choice * &s + &x * &constants::RISTRETTO_BASEPOINT_TABLE; let rc = r.compress(); let r_bytes = rc.as_bytes(); let receiver = Receiver { x: x, s: s, s_bytes: *s_bytes, r_bytes: *r_bytes, }; Some((receiver, *r_bytes)) } pub fn key<D>(self) -> GenericArray<u8, D::OutputSize> where D: Digest + Default, { let mut hash = D::default(); hash.input(self.s_bytes); hash.input(self.r_bytes); hash.input((&self.x * &self.s).compress().as_bytes()); hash.result() } } #[cfg(test)] mod tests { use super::{Receiver, Sender}; use rand::rngs::OsRng; use sha3::Sha3_256; #[test] fn test_ot() { let n = 10; let mut csprng = rand::rngs::OsRng; let (sender, s) = Sender::new(&mut csprng); for choice in 0..n { let (receiver, r) = Receiver::new(&mut csprng, choice, &s).unwrap(); let secret_s = sender.keys::<Sha3_256>(&r, n).unwrap(); let secret_r = receiver.key::<Sha3_256>(); assert_eq!(secret_r, secret_s[choice as usize]); } } }