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Tracking PR for v0.9.0 release (#278)

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* chore: update crate version to v0.9.0
* chore: remove deprecated re-exports
* chore: remove Box re-export
* feat: implement pure-Rust keygen and signing for RpoFalcon512 (#285)
* feat: add reproducible builds (#296)
* fix: address a few issues for migrating Miden VM  (#298)
* feat: add RngCore supertrait for FeltRng (#299)

---------

Co-authored-by: Al-Kindi-0 <82364884+Al-Kindi-0@users.noreply.github.com>
Co-authored-by: Paul-Henry Kajfasz <42912740+phklive@users.noreply.github.com>
This commit is contained in:
Bobbin Threadbare
2024-03-24 08:38:08 -07:00
committed by GitHub
parent 2be17b74fb
commit 5a2e917dd5
39 changed files with 5964 additions and 2334 deletions
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386
src/dsa/rpo_falcon512/keys/secret_key.rs Normal file
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use super::{
super::{
math::{ffldl, ffsampling, gram, normalize_tree, FalconFelt, FastFft, LdlTree, Polynomial},
signature::SignaturePoly,
ByteReader, ByteWriter, Deserializable, DeserializationError, Nonce, Serializable,
ShortLatticeBasis, Signature, Word, MODULUS, N, SIGMA, SIG_L2_BOUND,
},
PubKeyPoly, PublicKey,
};
use crate::dsa::rpo_falcon512::{
hash_to_point::hash_to_point_rpo256, math::ntru_gen, SIG_NONCE_LEN, SK_LEN,
};
use alloc::{string::ToString, vec::Vec};
use num::Complex;
use num_complex::Complex64;
use rand::Rng;
#[cfg(not(feature = "std"))]
use num::Float;
// CONSTANTS
// ================================================================================================
const WIDTH_BIG_POLY_COEFFICIENT: usize = 8;
const WIDTH_SMALL_POLY_COEFFICIENT: usize = 6;
// SECRET KEY
// ================================================================================================
/// The secret key is a quadruple [[g, -f], [G, -F]] of polynomials with integer coefficients. Each
/// polynomial is of degree at most N = 512 and computations with these polynomials is done modulo
/// the monic irreducible polynomial ϕ = x^N + 1. The secret key is a basis for a lattice and has
/// the property of being short with respect to a certain norm and an upper bound appropriate for
/// a given security parameter. The public key on the other hand is another basis for the same
/// lattice and can be described by a single polynomial h with integer coefficients modulo ϕ.
/// The two keys are related by the following relation:
///
/// 1. h = g /f [mod ϕ][mod p]
/// 2. f.G - g.F = p [mod ϕ]
///
/// where p = 12289 is the Falcon prime. Equation 2 is called the NTRU equation.
/// The secret key is generated by first sampling a random pair (f, g) of polynomials using
/// an appropriate distribution that yields short but not too short polynomials with integer
/// coefficients modulo ϕ. The NTRU equation is then used to find a matching pair (F, G).
/// The public key is then derived from the secret key using equation 1.
///
/// To allow for fast signature generation, the secret key is pre-processed into a more suitable
/// form, called the LDL tree, and this allows for fast sampling of short vectors in the lattice
/// using Fast Fourier sampling during signature generation (ffSampling algorithm 11 in [1]).
///
/// [1]: https://falcon-sign.info/falcon.pdf
#[derive(Debug, Clone)]
pub struct SecretKey {
secret_key: ShortLatticeBasis,
tree: LdlTree,
}
#[allow(clippy::new_without_default)]
impl SecretKey {
// CONSTRUCTORS
// --------------------------------------------------------------------------------------------
/// Generates a secret key from OS-provided randomness.
#[cfg(feature = "std")]
pub fn new() -> Self {
use rand::{rngs::StdRng, SeedableRng};
let mut rng = StdRng::from_entropy();
Self::with_rng(&mut rng)
}
/// Generates a secret_key using the provided random number generator `Rng`.
pub fn with_rng<R: Rng>(rng: &mut R) -> Self {
let basis = ntru_gen(N, rng);
Self::from_short_lattice_basis(basis)
}
/// Given a short basis [[g, -f], [G, -F]], computes the normalized LDL tree i.e., Falcon tree.
fn from_short_lattice_basis(basis: ShortLatticeBasis) -> SecretKey {
// FFT each polynomial of the short basis.
let basis_fft = to_complex_fft(&basis);
// compute the Gram matrix.
let gram_fft = gram(basis_fft);
// construct the LDL tree of the Gram matrix.
let mut tree = ffldl(gram_fft);
// normalize the leaves of the LDL tree.
normalize_tree(&mut tree, SIGMA);
Self { secret_key: basis, tree }
}
// PUBLIC ACCESSORS
// --------------------------------------------------------------------------------------------
/// Returns the polynomials of the short lattice basis of this secret key.
pub fn short_lattice_basis(&self) -> &ShortLatticeBasis {
&self.secret_key
}
/// Returns the public key corresponding to this secret key.
pub fn public_key(&self) -> PublicKey {
self.compute_pub_key_poly().into()
}
/// Returns the LDL tree associated to this secret key.
pub fn tree(&self) -> &LdlTree {
&self.tree
}
// SIGNATURE GENERATION
// --------------------------------------------------------------------------------------------
/// Signs a message with this secret key.
#[cfg(feature = "std")]
pub fn sign(&self, message: Word) -> Signature {
use rand::{rngs::StdRng, SeedableRng};
let mut rng = StdRng::from_entropy();
self.sign_with_rng(message, &mut rng)
}
/// Signs a message with the secret key relying on the provided randomness generator.
pub fn sign_with_rng<R: Rng>(&self, message: Word, rng: &mut R) -> Signature {
let mut nonce_bytes = [0u8; SIG_NONCE_LEN];
rng.fill_bytes(&mut nonce_bytes);
let nonce = Nonce::new(nonce_bytes);
let h = self.compute_pub_key_poly();
let c = hash_to_point_rpo256(message, &nonce);
let s2 = self.sign_helper(c, rng);
Signature::new(nonce, h, s2)
}
// HELPER METHODS
// --------------------------------------------------------------------------------------------
/// Derives the public key corresponding to this secret key using h = g /f [mod ϕ][mod p].
pub fn compute_pub_key_poly(&self) -> PubKeyPoly {
let g: Polynomial<FalconFelt> = self.secret_key[0].clone().into();
let g_fft = g.fft();
let minus_f: Polynomial<FalconFelt> = self.secret_key[1].clone().into();
let f = -minus_f;
let f_fft = f.fft();
let h_fft = g_fft.hadamard_div(&f_fft);
h_fft.ifft().into()
}
/// Signs a message polynomial with the secret key.
///
/// Takes a randomness generator implementing `Rng` and message polynomial representing `c`
/// the hash-to-point of the message to be signed. It outputs a signature polynomial `s2`.
fn sign_helper<R: Rng>(&self, c: Polynomial<FalconFelt>, rng: &mut R) -> SignaturePoly {
let one_over_q = 1.0 / (MODULUS as f64);
let c_over_q_fft = c.map(|cc| Complex::new(one_over_q * cc.value() as f64, 0.0)).fft();
// B = [[FFT(g), -FFT(f)], [FFT(G), -FFT(F)]]
let [g_fft, minus_f_fft, big_g_fft, minus_big_f_fft] = to_complex_fft(&self.secret_key);
let t0 = c_over_q_fft.hadamard_mul(&minus_big_f_fft);
let t1 = -c_over_q_fft.hadamard_mul(&minus_f_fft);
loop {
let bold_s = loop {
let z = ffsampling(&(t0.clone(), t1.clone()), &self.tree, rng);
let t0_min_z0 = t0.clone() - z.0;
let t1_min_z1 = t1.clone() - z.1;
// s = (t-z) * B
let s0 = t0_min_z0.hadamard_mul(&g_fft) + t1_min_z1.hadamard_mul(&big_g_fft);
let s1 =
t0_min_z0.hadamard_mul(&minus_f_fft) + t1_min_z1.hadamard_mul(&minus_big_f_fft);
// compute the norm of (s0||s1) and note that they are in FFT representation
let length_squared: f64 =
(s0.coefficients.iter().map(|a| (a * a.conj()).re).sum::<f64>()
+ s1.coefficients.iter().map(|a| (a * a.conj()).re).sum::<f64>())
/ (N as f64);
if length_squared > (SIG_L2_BOUND as f64) {
continue;
}
break [-s0, s1];
};
let s2 = bold_s[1].ifft();
let s2_coef: [i16; N] = s2
.coefficients
.iter()
.map(|a| a.re.round() as i16)
.collect::<Vec<i16>>()
.try_into()
.expect("The number of coefficients should be equal to N");
if let Ok(s2) = SignaturePoly::try_from(&s2_coef) {
return s2;
}
}
}
}
// SERIALIZATION / DESERIALIZATION
// ================================================================================================
impl Serializable for SecretKey {
fn write_into<W: ByteWriter>(&self, target: &mut W) {
let basis = &self.secret_key;
// header
let n = basis[0].coefficients.len();
let l = n.checked_ilog2().unwrap() as u8;
let header: u8 = (5 << 4) | l;
let f = &basis[1];
let g = &basis[0];
let capital_f = &basis[3];
let mut buffer = Vec::with_capacity(1281);
buffer.push(header);
let f_i8: Vec<i8> = f.coefficients.iter().map(|&a| -a as i8).collect();
let f_i8_encoded = encode_i8(&f_i8, WIDTH_SMALL_POLY_COEFFICIENT).unwrap();
buffer.extend_from_slice(&f_i8_encoded);
let g_i8: Vec<i8> = g.coefficients.iter().map(|&a| a as i8).collect();
let g_i8_encoded = encode_i8(&g_i8, WIDTH_SMALL_POLY_COEFFICIENT).unwrap();
buffer.extend_from_slice(&g_i8_encoded);
let big_f_i8: Vec<i8> = capital_f.coefficients.iter().map(|&a| -a as i8).collect();
let big_f_i8_encoded = encode_i8(&big_f_i8, WIDTH_BIG_POLY_COEFFICIENT).unwrap();
buffer.extend_from_slice(&big_f_i8_encoded);
target.write_bytes(&buffer);
}
}
impl Deserializable for SecretKey {
fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
let byte_vector: [u8; SK_LEN] = source.read_array()?;
// check length
if byte_vector.len() < 2 {
return Err(DeserializationError::InvalidValue("Invalid encoding length: Failed to decode as length is different from the one expected".to_string()));
}
// read fields
let header = byte_vector[0];
// check fixed bits in header
if (header >> 4) != 5 {
return Err(DeserializationError::InvalidValue("Invalid header format".to_string()));
}
// check log n
let logn = (header & 15) as usize;
let n = 1 << logn;
// match against const variant generic parameter
if n != N {
return Err(DeserializationError::InvalidValue(
"Unsupported Falcon DSA variant".to_string(),
));
}
if byte_vector.len() != SK_LEN {
return Err(DeserializationError::InvalidValue("Invalid encoding length: Failed to decode as length is different from the one expected".to_string()));
}
let chunk_size_f = ((n * WIDTH_SMALL_POLY_COEFFICIENT) + 7) >> 3;
let chunk_size_g = ((n * WIDTH_SMALL_POLY_COEFFICIENT) + 7) >> 3;
let chunk_size_big_f = ((n * WIDTH_BIG_POLY_COEFFICIENT) + 7) >> 3;
let f = decode_i8(&byte_vector[1..chunk_size_f + 1], WIDTH_SMALL_POLY_COEFFICIENT).unwrap();
let g = decode_i8(
&byte_vector[chunk_size_f + 1..(chunk_size_f + chunk_size_g + 1)],
WIDTH_SMALL_POLY_COEFFICIENT,
)
.unwrap();
let big_f = decode_i8(
&byte_vector[(chunk_size_f + chunk_size_g + 1)
..(chunk_size_f + chunk_size_g + chunk_size_big_f + 1)],
WIDTH_BIG_POLY_COEFFICIENT,
)
.unwrap();
let f = Polynomial::new(f.iter().map(|&c| FalconFelt::new(c.into())).collect());
let g = Polynomial::new(g.iter().map(|&c| FalconFelt::new(c.into())).collect());
let big_f = Polynomial::new(big_f.iter().map(|&c| FalconFelt::new(c.into())).collect());
// big_g * f - g * big_f = p (mod X^n + 1)
let big_g = g.fft().hadamard_div(&f.fft()).hadamard_mul(&big_f.fft()).ifft();
let basis = [
g.map(|f| f.balanced_value()),
-f.map(|f| f.balanced_value()),
big_g.map(|f| f.balanced_value()),
-big_f.map(|f| f.balanced_value()),
];
Ok(Self::from_short_lattice_basis(basis))
}
}
// HELPER FUNCTIONS
// ================================================================================================
/// Computes the complex FFT of the secret key polynomials.
fn to_complex_fft(basis: &[Polynomial<i16>; 4]) -> [Polynomial<Complex<f64>>; 4] {
let [g, f, big_g, big_f] = basis.clone();
let g_fft = g.map(|cc| Complex64::new(*cc as f64, 0.0)).fft();
let minus_f_fft = f.map(|cc| -Complex64::new(*cc as f64, 0.0)).fft();
let big_g_fft = big_g.map(|cc| Complex64::new(*cc as f64, 0.0)).fft();
let minus_big_f_fft = big_f.map(|cc| -Complex64::new(*cc as f64, 0.0)).fft();
[g_fft, minus_f_fft, big_g_fft, minus_big_f_fft]
}
/// Encodes a sequence of signed integers such that each integer x satisfies |x| < 2^(bits-1)
/// for a given parameter bits. bits can take either the value 6 or 8.
pub fn encode_i8(x: &[i8], bits: usize) -> Option<Vec<u8>> {
let maxv = (1 << (bits - 1)) - 1_usize;
let maxv = maxv as i8;
let minv = -maxv;
for &c in x {
if c > maxv || c < minv {
return None;
}
}
let out_len = ((N * bits) + 7) >> 3;
let mut buf = vec![0_u8; out_len];
let mut acc = 0_u32;
let mut acc_len = 0;
let mask = ((1_u16 << bits) - 1) as u8;
let mut input_pos = 0;
for &c in x {
acc = (acc << bits) | (c as u8 & mask) as u32;
acc_len += bits;
while acc_len >= 8 {
acc_len -= 8;
buf[input_pos] = (acc >> acc_len) as u8;
input_pos += 1;
}
}
if acc_len > 0 {
buf[input_pos] = (acc >> (8 - acc_len)) as u8;
}
Some(buf)
}
/// Decodes a sequence of bytes into a sequence of signed integers such that each integer x
/// satisfies |x| < 2^(bits-1) for a given parameter bits. bits can take either the value 6 or 8.
pub fn decode_i8(buf: &[u8], bits: usize) -> Option<Vec<i8>> {
let mut x = [0_i8; N];
let mut i = 0;
let mut j = 0;
let mut acc = 0_u32;
let mut acc_len = 0;
let mask = (1_u32 << bits) - 1;
let a = (1 << bits) as u8;
let b = ((1 << (bits - 1)) - 1) as u8;
while i < N {
acc = (acc << 8) | (buf[j] as u32);
j += 1;
acc_len += 8;
while acc_len >= bits && i < N {
acc_len -= bits;
let w = (acc >> acc_len) & mask;
let w = w as u8;
let z = if w > b { w as i8 - a as i8 } else { w as i8 };
x[i] = z;
i += 1;
}
}
if (acc & ((1u32 << acc_len) - 1)) == 0 {
Some(x.to_vec())
} else {
None
}
}