added garble example

pop-mpc/examples/garble.rs

@@ -0,0 +1,63 @@
+// This example demonstrates how to garble and evaluate an AES128 encryption circuit.
+// In practical situations wire labels would be communicated over a channel such as TCP and
+// using an oblivious transfer protocol. For simplicity, this example shows how the generator
+// and evaluator components work together in memory
+
+use aes::cipher::{generic_array::GenericArray, NewBlockCipher};
+use aes::Aes128;
+use pop_mpc::{
+    circuit::Circuit,
+    garble::{circuit::GarbledCircuit, evaluator::*, generator::*},
+    utils::boolvec_to_u8vec,
+};
+use rand::SeedableRng;
+use rand_chacha::ChaCha12Rng;
+
+fn bits_to_bytes(bits: &Vec<u8>) -> Vec<u8> {
+    let b: Vec<bool> = bits.iter().map(|b| *b == 1).collect();
+    boolvec_to_u8vec(&b)
+}
+
+fn main() {
+    let mut input = vec![0u8; 128];
+    let mut key = vec![0u8; 128];
+
+    println!(
+        "Input: {:02X?}\nKey: {:02X?}",
+        bits_to_bytes(&input),
+        bits_to_bytes(&key)
+    );
+
+    let mut rng = ChaCha12Rng::from_entropy();
+    let mut cipher = Aes128::new(GenericArray::from_slice(&[0u8; 16]));
+    let circ = Circuit::parse("circuits/aes_128_reverse.txt").unwrap();
+    let gen = HalfGateGenerator;
+    let ev = HalfGateEvaluator;
+
+    let gc: GarbledCircuit = gen.garble(&mut cipher, &mut rng, &circ).unwrap();
+
+    // Circuit operates on reversed bits
+    key.reverse();
+    input.reverse();
+
+    let inputs = [key, input].concat();
+    // Map input bits to corresponding wire labels
+    let input_labels = gc
+        .input_labels
+        .iter()
+        .zip(inputs)
+        .map(|(label, input)| label[input as usize])
+        .collect();
+
+    let output_labels = ev.eval(&mut cipher, &circ, &gc, input_labels).unwrap();
+
+    // Map output labels back to truth bits
+    let mut outputs: Vec<u8> = Vec::with_capacity(circ.noutput_wires);
+    for (i, label) in output_labels.iter().enumerate() {
+        outputs.push((label.lsb() ^ gc.output_bits[i]) as u8);
+    }
+
+    let mut ciphertext = bits_to_bytes(&outputs);
+    ciphertext.reverse();
+    println!("Ciphertext: {:02X?}", ciphertext);
+}