Add identify function

common/nym-compact-ecash/src/scheme/identify.rs

@@ -0,0 +1,12 @@
+use std::convert::TryFrom;
+
+use crate::error::Result;
+use crate::scheme::keygen::PublicKeyUser;
+use crate::scheme::setup::Parameters;
+use crate::scheme::spend::{PayInfo, Payment};
+
+pub fn identify(params: &Parameters, pay1: Payment, pay2: Payment, payInfo1: PayInfo, payInfo2: PayInfo) -> Result<PublicKeyUser> {
+    // TODO: We had to include checks for S1, S2 and payinfo1 and payinfo2
+    let pkUser = (pay2.T * pay1.R - pay1.T * pay2.R) * (pay1.R - pay2.R).invert().unwrap();
+    Ok(PublicKeyUser { pk: pkUser })
+}

common/nym-compact-ecash/src/scheme/mod.rs

@@ -15,6 +15,7 @@ pub mod keygen;
 pub mod setup;
 pub mod spend;
 pub mod withdrawal;
+pub mod identify;
 
 pub type SignerIndex = u64;
 

common/nym-compact-ecash/src/scheme/spend.rs

@@ -17,15 +17,15 @@ pub struct PayInfo {
 }
 
 pub struct Payment {
-    kappa: G2Projective,
-    sig: Signature,
-    S: G1Projective,
-    T: G1Projective,
-    A: G1Projective,
-    C: G1Projective,
-    D: G1Projective,
-    R: Scalar,
-    zk_proof: SpendProof,
+    pub kappa: G2Projective,
+    pub sig: Signature,
+    pub S: G1Projective,
+    pub T: G1Projective,
+    pub A: G1Projective,
+    pub C: G1Projective,
+    pub D: G1Projective,
+    pub R: Scalar,
+    pub zk_proof: SpendProof,
 }
 
 pub fn pseudorandom_fgv(params: &Parameters, v: Scalar, l: u64) -> G1Projective {
@@ -134,7 +134,7 @@ pub fn spend(params: &Parameters, wallet: &Wallet, verification_key: &Verificati
     Ok((pay, wallet_upd))
 }
 
-pub fn spend_verify(params: &Parameters, verification_key: VerificationKeyAuth, pay: Payment, payinfo: PayInfo) -> Result<bool> {
+pub fn spend_verify(params: &Parameters, verification_key: &VerificationKeyAuth, pay: &Payment, payinfo: &PayInfo) -> Result<bool> {
     if bool::from(pay.sig.0.is_identity()) {
         return Err(CompactEcashError::Spend(
             "The element h of the signature equals the identity".to_string(),

common/nym-compact-ecash/src/tests/e2e.rs

@@ -7,6 +7,7 @@ use crate::scheme::keygen::{
     generate_keypair_user, PublicKeyUser, SecretKeyUser, ttp_keygen, VerificationKeyAuth,
 };
 use crate::scheme::setup::Parameters;
+use crate::scheme::spend::{PayInfo, spend, spend_verify};
 use crate::scheme::withdrawal::{issue_verify, issue_wallet, withdrawal_request};
 
 #[test]
@@ -43,7 +44,16 @@ fn main() -> Result<(), CompactEcashError> {
         .collect();
 
     // Aggregate partial wallets
-    let aggr_wallet = aggregate_wallets(&params, &verification_key, &user_keypair.secret_key(), &unblinded_wallet_shares, &req_info);
+    let aggr_wallet = aggregate_wallets(&params, &verification_key, &user_keypair.secret_key(), &unblinded_wallet_shares, &req_info)?;
+
+    // Let's try to spend some coins
+    let payInfo = PayInfo {
+        info: [6u8; 32],
+    };
+
+    let (payment, upd_wallet) = spend(&params, &aggr_wallet, &verification_key, &user_keypair.secret_key(), &payInfo)?;
+
+    assert!(spend_verify(&params, &verification_key, &payment, &payInfo).unwrap());
 
     Ok(())
 }