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Use SSZ to_bytes() for public-key serialization (#25) #26

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Merged
noopur23 merged 1 commit into from
Dec 1, 2025
Merged

Use SSZ to_bytes() for public-key serialization (#25) #26

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50 changes: 20 additions & 30 deletions src/main.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,11 +3,14 @@ use std::io::Write;
use std::path::PathBuf;

use clap::{Parser, Subcommand};
use leansig::serialization::Serializable;
use leansig::signature::{
generalized_xmss::instantiations_poseidon_top_level::lifetime_2_to_the_32::hashing_optimized::SIGTopLevelTargetSumLifetime32Dim64Base8,
SignatureScheme,
};
use serde_json::Value;

// Type alias for the public key type
type PublicKeyType = <SIGTopLevelTargetSumLifetime32Dim64Base8 as SignatureScheme>::PublicKey;

/// A CLI tool to generate cryptographic keys for hash-based signatures.
#[derive(Parser, Debug)]
Expand Down Expand Up @@ -111,40 +114,27 @@ fn generate_keys(
}

/// Convert pubkey JSON file to hex string
/// Reads the JSON file, extracts root and parameter arrays,
/// converts each u32 to 4 bytes (little-endian), concatenates,
/// and returns hex string with "0x" prefix
/// Reads the JSON file, deserializes into PublicKey type using serde,
/// then uses SSZ serialization (to_bytes) to get canonical form bytes.
/// Returns hex string with "0x" prefix.
///
/// Note: The JSON file contains field elements in Montgomery form (internal representation).
/// We must use to_bytes() which performs SSZ serialization to get the canonical form
/// that is expected by from_bytes() during signature verification.
fn pubkey_json_to_hex(pk_file_path: &PathBuf) -> Result<String, Box<dyn std::error::Error>> {
// Read JSON file
let json_content = fs::read_to_string(pk_file_path)?;
let json: Value = serde_json::from_str(&json_content)?;

// Extract root array (8 u32 integers)
let root_array = json["root"]
.as_array()
.ok_or("Missing or invalid 'root' array")?;

// Extract parameter array (5 u32 integers)
let param_array = json["parameter"]
.as_array()
.ok_or("Missing or invalid 'parameter' array")?;

// Convert root array to bytes (little-endian)
let mut pubkey_bytes = Vec::new();
for val in root_array {
let num = val.as_u64().ok_or("Invalid number in root array")? as u32;
pubkey_bytes.extend_from_slice(&num.to_le_bytes());
}

// Convert parameter array to bytes (little-endian)
for val in param_array {
let num = val.as_u64().ok_or("Invalid number in parameter array")? as u32;
pubkey_bytes.extend_from_slice(&num.to_le_bytes());
}


// Deserialize into PublicKeyType using serde (this handles Montgomery form)
let public_key: PublicKeyType = serde_json::from_str(&json_content)?;

// Use to_bytes() which uses SSZ serialization (canonical form)
// This is the correct format expected by from_bytes() during verification
let pubkey_bytes = public_key.to_bytes();

// Convert bytes to hex string with "0x" prefix
let hex_string = format!("0x{}", hex::encode(&pubkey_bytes));

Ok(hex_string)
}

Expand Down