From 61275e80389f45d5ee24d6fd1d0679bd654e12d5 Mon Sep 17 00:00:00 2001
From: th4s <th4s@metavoid.xyz>
Date: Thu, 7 Mar 2024 18:15:00 +0100
Subject: [PATCH] Adds an ideal ROT functionality to mpz-ot-core (#102)

* Adds an ideal ROT functionality to mpz-ot-core

* Update ot/mpz-ot-core/src/ideal/ideal_rot.rs

Derive Debug for IdealROT

Co-authored-by: sinu.eth <65924192+sinui0@users.noreply.github.com>

* Add feedback

* Add more feedback

---------

Co-authored-by: sinu.eth <65924192+sinui0@users.noreply.github.com>
---
 crates/mpz-core/src/prg.rs                |  2 +
 crates/mpz-ot-core/src/ideal/ideal_rot.rs | 89 +++++++++++++++++++++++
 crates/mpz-ot-core/src/ideal/mod.rs       |  1 +
 3 files changed, 92 insertions(+)
 create mode 100644 crates/mpz-ot-core/src/ideal/ideal_rot.rs

diff --git a/crates/mpz-core/src/prg.rs b/crates/mpz-core/src/prg.rs
index 9d62587b..d49f8d03 100644
--- a/crates/mpz-core/src/prg.rs
+++ b/crates/mpz-core/src/prg.rs
@@ -71,6 +71,8 @@ impl CryptoRng for PrgCore {}
 #[derive(Clone)]
 pub struct Prg(BlockRng<PrgCore>);
 
+opaque_debug::implement!(Prg);
+
 impl RngCore for Prg {
     #[inline(always)]
     fn next_u32(&mut self) -> u32 {
diff --git a/crates/mpz-ot-core/src/ideal/ideal_rot.rs b/crates/mpz-ot-core/src/ideal/ideal_rot.rs
new file mode 100644
index 00000000..a5f2dfb8
--- /dev/null
+++ b/crates/mpz-ot-core/src/ideal/ideal_rot.rs
@@ -0,0 +1,89 @@
+//! Define ideal functionality of ROT with random choice bit.
+
+use mpz_core::{prg::Prg, Block};
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+/// The message that sender receives from the ROT functionality.
+pub struct RotMsgForSender {
+    /// The random blocks that sender receives from the ROT functionality.
+    pub qs: Vec<[Block; 2]>,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+/// The message that receiver receives from the ROT functionality.
+pub struct RotMsgForReceiver {
+    /// The random bits that receiver receives from the ROT functionality.
+    pub rs: Vec<bool>,
+    /// The chosen blocks that receiver receives from the ROT functionality.
+    pub ts: Vec<Block>,
+}
+
+/// An ideal functionality for random OT
+#[derive(Debug)]
+pub struct IdealROT {
+    counter: usize,
+    prg: Prg,
+}
+
+impl IdealROT {
+    /// Initiate the functionality
+    pub fn new() -> Self {
+        let prg = Prg::new();
+        IdealROT { counter: 0, prg }
+    }
+
+    /// Performs the extension with random choice bits.
+    ///
+    /// # Argument
+    ///
+    /// * `counter` - The number of ROT to extend.
+    pub fn extend(&mut self, counter: usize) -> (RotMsgForSender, RotMsgForReceiver) {
+        let mut qs1 = vec![Block::ZERO; counter];
+        let mut qs2 = vec![Block::ZERO; counter];
+
+        self.prg.random_blocks(&mut qs1);
+        self.prg.random_blocks(&mut qs2);
+
+        let qs: Vec<[Block; 2]> = qs1.iter().zip(qs2).map(|(&q1, q2)| [q1, q2]).collect();
+
+        let mut rs = vec![false; counter];
+
+        self.prg.random_bools(&mut rs);
+
+        let ts: Vec<Block> = qs
+            .iter()
+            .zip(rs.iter())
+            .map(|(&q, &r)| q[r as usize])
+            .collect();
+
+        self.counter += counter;
+        (RotMsgForSender { qs }, RotMsgForReceiver { rs, ts })
+    }
+}
+
+impl Default for IdealROT {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{IdealROT, RotMsgForReceiver};
+
+    #[test]
+    fn ideal_rot_test() {
+        let num = 100;
+        let mut ideal_rot = IdealROT::new();
+        let (sender, receiver) = ideal_rot.extend(num);
+
+        let qs = sender.qs;
+        let RotMsgForReceiver { rs, ts } = receiver;
+
+        qs.iter()
+            .zip(ts)
+            .zip(rs)
+            .for_each(|((q, t), r)| assert_eq!(q[r as usize], t));
+    }
+}
diff --git a/crates/mpz-ot-core/src/ideal/mod.rs b/crates/mpz-ot-core/src/ideal/mod.rs
index 1fb56072..ed22897e 100644
--- a/crates/mpz-ot-core/src/ideal/mod.rs
+++ b/crates/mpz-ot-core/src/ideal/mod.rs
@@ -1,4 +1,5 @@
 //! Define ideal functionalities of OTs.
 pub mod ideal_cot;
 pub mod ideal_mpcot;
+pub mod ideal_rot;
 pub mod ideal_spcot;