2025-08-12 04:23:00 +02:00

96 lines
2.3 KiB
Rust

#![no_std]
#![no_main]
extern crate alloc;
use alloc::vec;
use alloc::vec::Vec;
use risc0_zkvm::guest::env;
use hkdf::Hkdf;
use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};
use sha3::{digest::{ExtendableOutput, Update, XofReader}, Shake256};
//use serde_big_array::BigArray;
risc0_zkvm::guest::entry!(main);
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct KeystreamRequest {
pub kdf_salt: [u8; 32],
pub ss_bytes: [u8; 32],
pub epk_bytes: Vec<u8>,
pub ipk_bytes: Vec<u8>,
pub commitment: [u8; 32],
pub out_index: u32,
pub pt: Vec<u8>,
}
#[derive(Debug, Serialize, Deserialize)]
pub struct EncInput {
pub plaintext: Vec<u8>,
pub ss_bytes: [u8; 32],
pub epk_bytes: Vec<u8>,
pub ipk_bytes: Vec<u8>,
pub commitment: [u8; 32],
pub out_index: u32,
}
fn nssa_kdf(
ss_bytes: &[u8; 32],
epk: &[u8],
ipk: &[u8],
commitment: &[u8; 32],
out_index: u32,
) -> ([u8; 32], Vec<u8>) {
// salt = SHA256("NSSA/v0.1/KDF-SHA256")
let mut hasher = Sha256::new();
sha2::Digest::update(&mut hasher, b"NSSA/v0.1/KDF-SHA256");
let salt = hasher.finalize();
let hk = Hkdf::<Sha256>::new(Some(&salt), ss_bytes);
// info = "NSSA/v0.1/enc" || Epk || Ipk || commitment || le(out_index)
let mut info = Vec::with_capacity(3 + 33 + 33 + 32 + 4 + 16);
info.extend_from_slice(b"NSSA/v0.1/enc");
info.extend_from_slice(epk);
info.extend_from_slice(ipk);
info.extend_from_slice(commitment);
info.extend_from_slice(&out_index.to_le_bytes());
let mut k_enc = [0u8; 32];
hk.expand(&info, &mut k_enc).unwrap();
(k_enc, info)
}
fn enc_xor_shake256(k_enc: &[u8; 32], ad: &[u8], pt: &[u8]) -> Vec<u8> {
let mut shake = Shake256::default();
shake.update(b"NSSA/v0.1/ENC/SHAKE256");
shake.update(k_enc);
shake.update(ad);
let mut xof = shake.finalize_xof();
let mut ks = vec![0u8; pt.len()];
xof.read(&mut ks);
pt.iter().zip(ks).map(|(p, k)| p ^ k).collect()
}
pub fn main() {
let input: EncInput = env::read();
let (k_enc, info) = nssa_kdf(
&input.ss_bytes,
&input.epk_bytes,
&input.ipk_bytes,
&input.commitment,
input.out_index,
);
let ct = enc_xor_shake256(&k_enc, &info, &input.plaintext);
// Commit ciphertext to the journal
env::commit_slice(&ct);
}