Add function generating the payinfo

Cargo.lock

@@ -3138,6 +3138,7 @@ version = "0.1.0"
 dependencies = [
  "bls12_381 0.6.0",
  "bs58",
+ "chrono",
  "criterion",
  "digest 0.9.0",
  "ff 0.11.0",

common/nym_offline_compact_ecash/Cargo.toml

@@ -7,6 +7,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+chrono = "0.4.19"
 #bls12_381 = { version = "0.5", default-features = false, features = ["pairings", "alloc", "experimental"] }
 bls12_381 = { path = "/Users/ania/Documents/Git/andrew_bls12_381", default-features = false, features = ["alloc", "pairings", "experimental", "zeroize"] }
 itertools = "0.10"

common/nym_offline_compact_ecash/src/scheme/mod.rs

@@ -6,12 +6,14 @@ use group::Curve;
 use crate::Attribute;
 use crate::error::{CompactEcashError, Result};
 use crate::proofs::proof_spend::{SpendInstance, SpendProof, SpendWitness};
-use crate::scheme::keygen::{SecretKeyUser, VerificationKeyAuth};
+use crate::scheme::keygen::{SecretKeyUser, VerificationKeyAuth, PublicKeyUser};
 use crate::scheme::setup::{GroupParameters, Parameters};
 use crate::utils::{
     check_bilinear_pairing, hash_to_scalar, Signature, SignerIndex,
     try_deserialize_g1_projective, try_deserialize_scalar, try_deserialize_g2_projective,
 };
+use chrono::{Utc, Timelike};
+use rand::{Rng, thread_rng};
 
 pub mod aggregation;
 pub mod identify;
@@ -312,6 +314,24 @@ pub struct PayInfo {
     pub info: [u8; 32],
 }
 
+pub fn generate_payinfo(provider_pk: PublicKeyUser) -> Vec<u8>{
+    let mut rng = thread_rng();
+    let mut rbytes = [0u8; 32];
+    rng.fill(&mut rbytes);
+
+    let timestamp = Utc::now().timestamp();
+    let timestamp_bytes: [u8; 8] = timestamp.to_be_bytes();
+
+    let ppk_bytes = provider_pk.pk.to_affine().to_compressed();
+
+    let mut payinfo = Vec::with_capacity(32 + 8 +48);
+    payinfo.extend_from_slice(&rbytes);
+    payinfo.extend_from_slice(&timestamp_bytes);
+    payinfo.extend_from_slice(&ppk_bytes);
+    
+    payinfo
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub struct Payment {
     pub kappa: G2Projective,