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// Copyright (C) 2019-2023 Aleo Systems Inc.
// This file is part of the snarkVM library.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at:
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use super::*;
impl<N: Network> Request<N> {
/// Returns the request for a given private key, program ID, function name, inputs, input types, and RNG, where:
/// challenge := HashToScalar(r * G, pk_sig, pr_sig, caller, \[tvk, tcm, function ID, input IDs\])
/// response := r - challenge * sk_sig
pub fn sign<R: Rng + CryptoRng>(
private_key: &PrivateKey<N>,
program_id: ProgramID<N>,
function_name: Identifier<N>,
inputs: impl ExactSizeIterator<Item = impl TryInto<Value<N>>>,
input_types: &[ValueType<N>],
rng: &mut R,
) -> Result<Self> {
// Ensure the number of inputs matches the number of input types.
if input_types.len() != inputs.len() {
bail!(
"Function '{}' in the program '{}' expects {} inputs, but {} were provided.",
function_name,
program_id,
input_types.len(),
inputs.len()
)
}
// Retrieve `sk_sig`.
let sk_sig = private_key.sk_sig();
// Derive the compute key.
let compute_key = ComputeKey::try_from(private_key)?;
// Retrieve `pk_sig`.
let pk_sig = compute_key.pk_sig();
// Retrieve `pr_sig`.
let pr_sig = compute_key.pr_sig();
// Derive the view key.
let view_key = ViewKey::try_from((private_key, &compute_key))?;
// Derive `sk_tag` from the graph key.
let sk_tag = GraphKey::try_from(view_key)?.sk_tag();
// Sample a random nonce.
let nonce = Field::<N>::rand(rng);
// Compute a `r` as `HashToScalar(sk_sig || nonce)`. Note: This is the transition secret key `tsk`.
let r = N::hash_to_scalar_psd4(&[N::serial_number_domain(), sk_sig.to_field()?, nonce])?;
// Compute `g_r` as `r * G`. Note: This is the transition public key `tpk`.
let g_r = N::g_scalar_multiply(&r);
// Derive the caller from the compute key.
let caller = Address::try_from(compute_key)?;
// Compute the transition view key `tvk` as `r * caller`.
let tvk = (*caller * r).to_x_coordinate();
// Compute the transition commitment `tcm` as `Hash(tvk)`.
let tcm = N::hash_psd2(&[tvk])?;
// Compute the function ID as `Hash(network_id, program_id, function_name)`.
let function_id = N::hash_bhp1024(
&(U16::<N>::new(N::ID), program_id.name(), program_id.network(), function_name).to_bits_le(),
)?;
// Construct the hash input as `(r * G, pk_sig, pr_sig, caller, [tvk, tcm, function ID, input IDs])`.
let mut message = Vec::with_capacity(5 + 2 * inputs.len());
message.extend([g_r, pk_sig, pr_sig, *caller].map(|point| point.to_x_coordinate()));
message.extend([tvk, tcm, function_id]);
// Initialize a vector to store the prepared inputs.
let mut prepared_inputs = Vec::with_capacity(inputs.len());
// Initialize a vector to store the input IDs.
let mut input_ids = Vec::with_capacity(inputs.len());
// Prepare the inputs.
for (index, (input, input_type)) in inputs.zip_eq(input_types).enumerate() {
// Prepare the input.
let input = input.try_into().map_err(|_| {
anyhow!("Failed to parse input #{index} ('{input_type}') for '{program_id}/{function_name}'")
})?;
// Store the prepared input.
prepared_inputs.push(input.clone());
match input_type {
// A constant input is hashed (using `tcm`) to a field element.
ValueType::Constant(..) => {
// Ensure the input is a plaintext.
ensure!(matches!(input, Value::Plaintext(..)), "Expected a plaintext input");
// Construct the (console) input index as a field element.
let index = Field::from_u16(u16::try_from(index).or_halt_with::<N>("Input index exceeds u16"));
// Construct the preimage as `(function ID || input || tcm || index)`.
let mut preimage = vec![function_id];
preimage.extend(input.to_fields()?);
preimage.push(tcm);
preimage.push(index);
// Hash the input to a field element.
let input_hash = N::hash_psd8(&preimage)?;
// Add the input hash to the preimage.
message.push(input_hash);
// Add the input ID to the inputs.
input_ids.push(InputID::Constant(input_hash));
}
// A public input is hashed (using `tcm`) to a field element.
ValueType::Public(..) => {
// Ensure the input is a plaintext.
ensure!(matches!(input, Value::Plaintext(..)), "Expected a plaintext input");
// Construct the (console) input index as a field element.
let index = Field::from_u16(u16::try_from(index).or_halt_with::<N>("Input index exceeds u16"));
// Construct the preimage as `(function ID || input || tcm || index)`.
let mut preimage = vec![function_id];
preimage.extend(input.to_fields()?);
preimage.push(tcm);
preimage.push(index);
// Hash the input to a field element.
let input_hash = N::hash_psd8(&preimage)?;
// Add the input hash to the preimage.
message.push(input_hash);
// Add the input ID to the inputs.
input_ids.push(InputID::Public(input_hash));
}
// A private input is encrypted (using `tvk`) and hashed to a field element.
ValueType::Private(..) => {
// Ensure the input is a plaintext.
ensure!(matches!(input, Value::Plaintext(..)), "Expected a plaintext input");
// Construct the (console) input index as a field element.
let index = Field::from_u16(u16::try_from(index).or_halt_with::<N>("Input index exceeds u16"));
// Compute the input view key as `Hash(function ID || tvk || index)`.
let input_view_key = N::hash_psd4(&[function_id, tvk, index])?;
// Compute the ciphertext.
let ciphertext = match &input {
Value::Plaintext(plaintext) => plaintext.encrypt_symmetric(input_view_key)?,
// Ensure the input is a plaintext.
Value::Record(..) => bail!("Expected a plaintext input, found a record input"),
};
// Hash the ciphertext to a field element.
let input_hash = N::hash_psd8(&ciphertext.to_fields()?)?;
// Add the input hash to the preimage.
message.push(input_hash);
// Add the input hash to the inputs.
input_ids.push(InputID::Private(input_hash));
}
// A record input is computed to its serial number.
ValueType::Record(record_name) => {
// Retrieve the record.
let record = match &input {
Value::Record(record) => record,
// Ensure the input is a record.
Value::Plaintext(..) => bail!("Expected a record input, found a plaintext input"),
};
// Ensure the record belongs to the caller.
ensure!(**record.owner() == caller, "Input record for '{program_id}' must belong to the signer");
// Compute the record commitment.
let commitment = record.to_commitment(&program_id, record_name)?;
// Compute the generator `H` as `HashToGroup(commitment)`.
let h = N::hash_to_group_psd2(&[N::serial_number_domain(), commitment])?;
// Compute `h_r` as `r * H`.
let h_r = h * r;
// Compute `gamma` as `sk_sig * H`.
let gamma = h * sk_sig;
// Compute the `serial_number` from `gamma`.
let serial_number = Record::<N, Plaintext<N>>::serial_number_from_gamma(&gamma, commitment)?;
// Compute the tag.
let tag = Record::<N, Plaintext<N>>::tag(sk_tag, commitment)?;
// Add (`H`, `r * H`, `gamma`, `tag`) to the preimage.
message.extend([h, h_r, gamma].iter().map(|point| point.to_x_coordinate()));
message.push(tag);
// Add the input ID.
input_ids.push(InputID::Record(commitment, gamma, serial_number, tag));
}
// An external record input is hashed (using `tvk`) to a field element.
ValueType::ExternalRecord(..) => {
// Ensure the input is a record.
ensure!(matches!(input, Value::Record(..)), "Expected a record input");
// Construct the (console) input index as a field element.
let index = Field::from_u16(u16::try_from(index).or_halt_with::<N>("Input index exceeds u16"));
// Construct the preimage as `(function ID || input || tvk || index)`.
let mut preimage = vec![function_id];
preimage.extend(input.to_fields()?);
preimage.push(tvk);
preimage.push(index);
// Hash the input to a field element.
let input_hash = N::hash_psd8(&preimage)?;
// Add the input hash to the preimage.
message.push(input_hash);
// Add the input hash to the inputs.
input_ids.push(InputID::ExternalRecord(input_hash));
}
}
}
// Compute `challenge` as `HashToScalar(r * G, pk_sig, pr_sig, caller, [tvk, tcm, function ID, input IDs])`.
let challenge = N::hash_to_scalar_psd8(&message)?;
// Compute `response` as `r - challenge * sk_sig`.
let response = r - challenge * sk_sig;
Ok(Self {
caller,
network_id: U16::new(N::ID),
program_id,
function_name,
input_ids,
inputs: prepared_inputs,
signature: Signature::from((challenge, response, compute_key)),
sk_tag,
tvk,
tsk: r,
tcm,
})
}
}