Add ServerKeyState for key synchronization

ppoprf/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ppoprf"
-version = "0.3.1"
+version = "0.4.0"
 authors = ["Alex Davidson <coela@alxdavids.xyz>", "Ralph Ankele <rankele@brave.com>"]
 description = "Puncturable Partially-Oblivious Pseudo-Random Function"
 documentation = "https://docs.rs/ppoprf"
@@ -12,9 +12,9 @@ edition = "2021"
 
 [dependencies]
 rand = { version = "0.8.5", features = [ "getrandom" ] }
-bitvec = "1.0.1"
+bitvec = { version = "1.0.1", features = ["serde"] }
 curve25519-dalek =  { version = "4.0.0", features = [ "rand_core", "serde" ] }
-serde = "1.0.147"
+serde = { version = "1.0.147", features = ["derive"] }
 strobe-rs = "0.8.1"
 base64 = "0.13.0"
 bincode = "1.3.3"

ppoprf/src/ggm.rs

@@ -10,11 +10,12 @@ use crate::strobe_rng::StrobeRng;
 use bitvec::prelude::*;
 use rand::rngs::OsRng;
 use rand::Rng;
+use serde::{Deserialize, Serialize};
 use strobe_rs::{SecParam, Strobe};
 
 use zeroize::{Zeroize, ZeroizeOnDrop};
 
-#[derive(Clone, Eq, PartialEq)]
+#[derive(Clone, Eq, PartialEq, Serialize, Deserialize)]
 struct Prefix {
   bits: BitVec<usize, bitvec::order::Lsb0>,
 }
@@ -31,11 +32,15 @@ impl Prefix {
 
 impl fmt::Debug for Prefix {
   fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    f.debug_struct("Prefix").field("bits", &self.bits).finish()
+    f.debug_struct("Prefix")
+      .field("bits", &self.bits.as_raw_slice().to_vec())
+      .finish()
   }
 }
 
-#[derive(Clone, Zeroize, ZeroizeOnDrop)]
+#[derive(
+  Debug, Clone, Zeroize, ZeroizeOnDrop, Serialize, Deserialize, PartialEq, Eq,
+)]
 struct GGMPseudorandomGenerator {
   key: [u8; 32],
 }
@@ -59,8 +64,10 @@ impl GGMPseudorandomGenerator {
   }
 }
 
-#[derive(Clone, Zeroize, ZeroizeOnDrop)]
-struct GGMPuncturableKey {
+#[derive(
+  Debug, Clone, Zeroize, ZeroizeOnDrop, Serialize, Deserialize, Eq, PartialEq,
+)]
+pub(crate) struct GGMPuncturableKey {
   prgs: Vec<GGMPseudorandomGenerator>,
   #[zeroize(skip)]
   prefixes: Vec<(Prefix, Vec<u8>)>,
@@ -125,7 +132,7 @@ impl GGMPuncturableKey {
 #[derive(Clone, Zeroize, ZeroizeOnDrop)]
 pub struct GGM {
   inp_len: usize,
-  key: GGMPuncturableKey,
+  pub(crate) key: GGMPuncturableKey,
 }
 
 impl GGM {

ppoprf/src/ppoprf.rs

@@ -23,6 +23,7 @@ use serde::{de, ser, Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::convert::TryInto;
 
+use crate::ggm::GGMPuncturableKey;
 use crate::strobe_rng::StrobeRng;
 use strobe_rs::{SecParam, Strobe};
 
@@ -192,7 +193,7 @@ impl ProofDLEQ {
 
 // Server public key structure for PPOPRF, contains all elements of the
 // form g^{sk_0},g^{t_i} for metadata tags t_i.
-#[derive(Deserialize, Serialize, Clone, Debug)]
+#[derive(Deserialize, Serialize, Clone, Debug, Eq, PartialEq)]
 pub struct ServerPublicKey {
   base_pk: Point,
   md_pks: BTreeMap<u8, Point>,
@@ -301,6 +302,36 @@ where
   Ok(Point(CompressedRistretto(fixed_data)))
 }
 
+/// Structure containing all relevant key information
+/// for syncing between Server instances.
+/// To be used for deserialization.
+#[derive(Deserialize)]
+pub struct ServerKeyState {
+  oprf_key: RistrettoScalar,
+  public_key: ServerPublicKey,
+  ggm_key: GGMPuncturableKey,
+}
+
+/// Structure containing all relevant key information
+/// for syncing between Server instances.
+/// To be used for serialization.
+#[derive(Serialize, Eq, PartialEq, Debug)]
+pub struct ServerKeyStateRef<'a> {
+  oprf_key: &'a RistrettoScalar,
+  public_key: &'a ServerPublicKey,
+  ggm_key: &'a GGMPuncturableKey,
+}
+
+impl ServerKeyState {
+  pub fn as_ref(&self) -> ServerKeyStateRef<'_> {
+    ServerKeyStateRef {
+      oprf_key: &self.oprf_key,
+      public_key: &self.public_key,
+      ggm_key: &self.ggm_key,
+    }
+  }
+}
+
 // The `Server` runs the server-side component of the PPOPRF protocol.
 #[derive(Clone, Zeroize, ZeroizeOnDrop)]
 pub struct Server {
@@ -370,6 +401,20 @@ impl Server {
   pub fn get_public_key(&self) -> ServerPublicKey {
     self.public_key.clone()
   }
+
+  pub fn get_private_key(&self) -> ServerKeyStateRef<'_> {
+    ServerKeyStateRef {
+      oprf_key: &self.oprf_key,
+      public_key: &self.public_key,
+      ggm_key: &self.pprf.key,
+    }
+  }
+
+  pub fn set_private_key(&mut self, private_key: ServerKeyState) {
+    self.oprf_key = private_key.oprf_key;
+    self.public_key = private_key.public_key;
+    self.pprf.key = private_key.ggm_key;
+  }
 }
 
 // The `Client` struct is essentially a collection of static functions

star/Cargo.toml

@@ -13,7 +13,7 @@ edition = "2018"
 [dependencies]
 strobe-rs = "0.8.1"
 adss = { path = "../adss", version = "0.2.2" }
-ppoprf = { path = "../ppoprf", version = "0.3.0" }
+ppoprf = { path = "../ppoprf", version = "0.4.0" }
 rand = "0.8.5"
 rand_core = "0.6.4"
 zeroize = "1.5.5"