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-rw-r--r--src/hibe/bbg.rs320
1 files changed, 320 insertions, 0 deletions
diff --git a/src/hibe/bbg.rs b/src/hibe/bbg.rs
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+++ b/src/hibe/bbg.rs
@@ -0,0 +1,320 @@
+use std::iter;
+
+use super::{Hibe, HibeCrypt, HibeKem};
+use crate::error::{Error, Result};
+
+use bls12_381_plus::{
+ ff::Field, group::Group, pairing, G1Affine, G2Affine, G2Projective, Gt, Scalar,
+};
+use rand::Rng;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct BonehBoyenGoh {
+ max_depth: usize,
+}
+
+impl BonehBoyenGoh {
+ pub fn new(max_depth: usize) -> Self {
+ Self { max_depth }
+ }
+
+ pub fn max_depth(&self) -> usize {
+ self.max_depth
+ }
+}
+
+impl Hibe for BonehBoyenGoh {
+ type PrivateKey = (G2Affine, G1Affine, Vec<G2Affine>);
+ type MasterKey = G2Affine;
+ type PublicKey = (G1Affine, G1Affine, G2Affine, G2Affine, Vec<G2Affine>);
+ type Identity = Scalar;
+
+ fn setup<R: Rng>(&self, mut rng: R) -> Result<(Self::PublicKey, Self::MasterKey)> {
+ let g = G1Affine::generator();
+ let alpha = Scalar::random(&mut rng);
+ let g1 = g * alpha;
+ let g2 = G2Projective::random(&mut rng);
+ let g3 = G2Projective::random(&mut rng);
+ let hs = (0..self.max_depth())
+ .map(|_| G2Projective::random(&mut rng))
+ .map(Into::into)
+ .collect();
+ Ok((
+ (g, g1.into(), g2.into(), g3.into(), hs),
+ (g2 * alpha).into(),
+ ))
+ }
+
+ fn generate_key<R: Rng>(
+ &self,
+ rng: R,
+ public_key: &Self::PublicKey,
+ master_key: &Self::MasterKey,
+ identity: &[Self::Identity],
+ ) -> Result<Self::PrivateKey> {
+ if identity.len() > self.max_depth() {
+ return Err(Error::IdentityTooLong);
+ }
+
+ let r = Scalar::random(rng);
+ Ok((
+ (master_key
+ + (public_key
+ .4
+ .iter()
+ .zip(identity)
+ .map(|(h, i)| h * i)
+ .sum::<G2Projective>()
+ + public_key.3)
+ * r)
+ .into(),
+ (public_key.0 * r).into(),
+ public_key.4[identity.len()..]
+ .iter()
+ .map(|h| (h * r).into())
+ .collect(),
+ ))
+ }
+
+ fn derive_key<R: Rng>(
+ &self,
+ rng: R,
+ public_key: &Self::PublicKey,
+ parent_key: &Self::PrivateKey,
+ parent_name: &[Self::Identity],
+ child: &Self::Identity,
+ ) -> Result<Self::PrivateKey> {
+ if parent_name.len() > self.max_depth() - 1 {
+ return Err(Error::IdentityTooLong);
+ }
+
+ let t = Scalar::random(rng);
+ Ok((
+ (parent_key.0
+ + parent_key.2[0] * child
+ + (public_key
+ .4
+ .iter()
+ .zip(parent_name.iter().chain(iter::once(child)))
+ .map(|(h, i)| h * i)
+ .sum::<G2Projective>()
+ + public_key.3)
+ * t)
+ .into(),
+ (parent_key.1 + public_key.0 * t).into(),
+ parent_key.2[1..]
+ .iter()
+ .zip(public_key.4[parent_name.len() + 1..].iter())
+ .map(|(b, h)| b + h * t)
+ .map(Into::into)
+ .collect(),
+ ))
+ }
+}
+
+impl HibeCrypt for BonehBoyenGoh {
+ type Message = Gt;
+
+ type Ciphertext = (Gt, G1Affine, G2Affine);
+
+ fn encrypt<R: Rng>(
+ &self,
+ rng: R,
+ public_key: &Self::PublicKey,
+ identity: &[Self::Identity],
+ message: &Self::Message,
+ ) -> Result<Self::Ciphertext> {
+ if identity.len() > self.max_depth() {
+ return Err(Error::IdentityTooLong);
+ }
+
+ let s = Scalar::random(rng);
+ Ok((
+ pairing(&public_key.1, &public_key.2) * s + message,
+ (public_key.0 * s).into(),
+ ((public_key
+ .4
+ .iter()
+ .zip(identity.iter())
+ .map(|(h, i)| h * i)
+ .sum::<G2Projective>()
+ + public_key.3)
+ * s)
+ .into(),
+ ))
+ }
+
+ fn decrypt(
+ &self,
+ _: &Self::PublicKey,
+ key: &Self::PrivateKey,
+ ciphertext: &Self::Ciphertext,
+ ) -> Result<Self::Message> {
+ let (a, b, c) = ciphertext;
+ Ok(a + pairing(&key.1, c) - pairing(b, &key.0))
+ }
+}
+
+impl HibeKem for BonehBoyenGoh {
+ type Key = Gt;
+
+ type EncapsulatedKey = (G1Affine, G2Affine);
+
+ fn encapsulate<R: Rng>(
+ &self,
+ rng: R,
+ public_key: &Self::PublicKey,
+ identity: &[Self::Identity],
+ ) -> Result<(Self::Key, Self::EncapsulatedKey)> {
+ if identity.len() > self.max_depth() {
+ return Err(Error::IdentityTooLong);
+ }
+
+ let s = Scalar::random(rng);
+ Ok((
+ pairing(&public_key.1, &public_key.2) * s,
+ (
+ (public_key.0 * s).into(),
+ ((public_key
+ .4
+ .iter()
+ .zip(identity.iter())
+ .map(|(h, i)| h * i)
+ .sum::<G2Projective>()
+ + public_key.3)
+ * s)
+ .into(),
+ ),
+ ))
+ }
+
+ fn decapsulate(
+ &self,
+ _: &Self::PublicKey,
+ key: &Self::PrivateKey,
+ encapsulation: &Self::EncapsulatedKey,
+ ) -> Result<Self::Key> {
+ let (b, c) = encapsulation;
+ Ok(-pairing(&key.1, c) + pairing(b, &key.0))
+ }
+}
+
+#[cfg(test)]
+mod test {
+ use super::*;
+
+ #[test]
+ fn encrypt_decrypt_empty_identity() {
+ let mut rng = rand::thread_rng();
+ let bbg = BonehBoyenGoh::new(5);
+ let (public_key, master_key) = bbg.setup(&mut rng).unwrap();
+ let identity = &[];
+ let secret_key = bbg
+ .generate_key(&mut rng, &public_key, &master_key, identity.as_slice())
+ .unwrap();
+ let message = Gt::generator() * Scalar::from(4u32);
+ let ciphertext = bbg
+ .encrypt(&mut rng, &public_key, identity.as_slice(), &message)
+ .unwrap();
+ let decryption = bbg.decrypt(&public_key, &secret_key, &ciphertext).unwrap();
+ assert_eq!(message, decryption);
+ }
+
+ #[test]
+ fn encrypt_decrypt_keygen() {
+ let mut rng = rand::thread_rng();
+ let bbg = BonehBoyenGoh::new(5);
+ let (public_key, master_key) = bbg.setup(&mut rng).unwrap();
+ let identity = &[Scalar::from(1u32), Scalar::from(2u32), Scalar::from(3u32)];
+ let secret_key = bbg
+ .generate_key(&mut rng, &public_key, &master_key, identity.as_slice())
+ .unwrap();
+ let message = Gt::generator() * Scalar::from(4u32);
+ let ciphertext = bbg
+ .encrypt(&mut rng, &public_key, identity.as_slice(), &message)
+ .unwrap();
+ let decryption = bbg.decrypt(&public_key, &secret_key, &ciphertext).unwrap();
+ assert_eq!(message, decryption);
+ }
+
+ #[test]
+ fn encrypt_decrypt_derived() {
+ let mut rng = rand::thread_rng();
+ let bbg = BonehBoyenGoh::new(5);
+ let (public_key, master_key) = bbg.setup(&mut rng).unwrap();
+ let identity = &[Scalar::from(1u32), Scalar::from(2u32), Scalar::from(3u32)];
+ let secret_key_0 = bbg
+ .generate_key(&mut rng, &public_key, &master_key, &[])
+ .unwrap();
+ let secret_key_1 = bbg
+ .derive_key(
+ &mut rng,
+ &public_key,
+ &secret_key_0,
+ &identity[..0],
+ &identity[0],
+ )
+ .unwrap();
+ let secret_key_2 = bbg
+ .derive_key(
+ &mut rng,
+ &public_key,
+ &secret_key_1,
+ &identity[..1],
+ &identity[1],
+ )
+ .unwrap();
+ let secret_key_3 = bbg
+ .derive_key(
+ &mut rng,
+ &public_key,
+ &secret_key_2,
+ &identity[..2],
+ &identity[2],
+ )
+ .unwrap();
+ let message = Gt::generator() * Scalar::from(4u32);
+ let ciphertext = bbg
+ .encrypt(&mut rng, &public_key, identity.as_slice(), &message)
+ .unwrap();
+ let decryption = bbg
+ .decrypt(&public_key, &secret_key_3, &ciphertext)
+ .unwrap();
+ assert_eq!(message, decryption);
+ }
+
+ #[test]
+ fn encrypt_decrypt_wrong_id() {
+ let mut rng = rand::thread_rng();
+ let bbg = BonehBoyenGoh::new(5);
+ let (public_key, master_key) = bbg.setup(&mut rng).unwrap();
+ let identity = &[Scalar::from(1u32), Scalar::from(2u32), Scalar::from(3u32)];
+ let secret_key = bbg
+ .generate_key(&mut rng, &public_key, &master_key, identity.as_slice())
+ .unwrap();
+ let message = Gt::generator() * Scalar::from(4u32);
+ let ciphertext = bbg
+ .encrypt(&mut rng, &public_key, &identity[..1], &message)
+ .unwrap();
+ let decryption = bbg.decrypt(&public_key, &secret_key, &ciphertext).unwrap();
+ assert_ne!(message, decryption);
+ }
+
+ #[test]
+ fn encapsulate_decapsulate_keygen() {
+ let mut rng = rand::thread_rng();
+ let bbg = BonehBoyenGoh::new(5);
+ let (public_key, master_key) = bbg.setup(&mut rng).unwrap();
+ let identity = &[Scalar::from(1u32), Scalar::from(2u32), Scalar::from(3u32)];
+ let secret_key = bbg
+ .generate_key(&mut rng, &public_key, &master_key, identity.as_slice())
+ .unwrap();
+ let (generated_key, encapsulated_key) = bbg
+ .encapsulate(&mut rng, &public_key, identity.as_slice())
+ .unwrap();
+ let decapsulated_key = bbg
+ .decapsulate(&public_key, &secret_key, &encapsulated_key)
+ .unwrap();
+ assert_eq!(generated_key, decapsulated_key);
+ }
+}
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