2022-12-27 09:32:52 +05:30
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/*
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*
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* Copyright (c) 2020-2022 Project CHIP Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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2023-02-02 18:22:21 +00:00
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use alloc::sync::Arc;
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use core::ops::{Mul, Sub};
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2022-12-27 09:32:52 +05:30
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use crate::error::Error;
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use byteorder::{ByteOrder, LittleEndian};
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use log::error;
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use mbedtls::{
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bignum::Mpi,
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ecp::EcPoint,
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hash::Md,
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pk::{EcGroup, EcGroupId, Pk},
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rng::{CtrDrbg, OsEntropy},
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};
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2023-02-02 18:22:21 +00:00
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extern crate alloc;
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2022-12-27 09:32:52 +05:30
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const MATTER_M_BIN: [u8; 65] = [
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0x04, 0x88, 0x6e, 0x2f, 0x97, 0xac, 0xe4, 0x6e, 0x55, 0xba, 0x9d, 0xd7, 0x24, 0x25, 0x79, 0xf2,
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0x99, 0x3b, 0x64, 0xe1, 0x6e, 0xf3, 0xdc, 0xab, 0x95, 0xaf, 0xd4, 0x97, 0x33, 0x3d, 0x8f, 0xa1,
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0x2f, 0x5f, 0xf3, 0x55, 0x16, 0x3e, 0x43, 0xce, 0x22, 0x4e, 0x0b, 0x0e, 0x65, 0xff, 0x02, 0xac,
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0x8e, 0x5c, 0x7b, 0xe0, 0x94, 0x19, 0xc7, 0x85, 0xe0, 0xca, 0x54, 0x7d, 0x55, 0xa1, 0x2e, 0x2d,
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0x20,
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];
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const MATTER_N_BIN: [u8; 65] = [
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0x04, 0xd8, 0xbb, 0xd6, 0xc6, 0x39, 0xc6, 0x29, 0x37, 0xb0, 0x4d, 0x99, 0x7f, 0x38, 0xc3, 0x77,
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0x07, 0x19, 0xc6, 0x29, 0xd7, 0x01, 0x4d, 0x49, 0xa2, 0x4b, 0x4f, 0x98, 0xba, 0xa1, 0x29, 0x2b,
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0x49, 0x07, 0xd6, 0x0a, 0xa6, 0xbf, 0xad, 0xe4, 0x50, 0x08, 0xa6, 0x36, 0x33, 0x7f, 0x51, 0x68,
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0xc6, 0x4d, 0x9b, 0xd3, 0x60, 0x34, 0x80, 0x8c, 0xd5, 0x64, 0x49, 0x0b, 0x1e, 0x65, 0x6e, 0xdb,
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0xe7,
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];
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#[allow(non_snake_case)]
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2023-02-02 18:22:21 +00:00
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pub struct CryptoSpake2 {
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group: EcGroup,
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order: Mpi,
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xy: Mpi,
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w0: Mpi,
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w1: Mpi,
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M: EcPoint,
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N: EcPoint,
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L: EcPoint,
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pB: EcPoint,
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}
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2023-02-02 18:22:21 +00:00
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impl CryptoSpake2 {
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2022-12-27 09:32:52 +05:30
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#[allow(non_snake_case)]
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pub fn new() -> Result<Self, Error> {
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2022-12-27 09:32:52 +05:30
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let group = EcGroup::new(mbedtls::pk::EcGroupId::SecP256R1)?;
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let order = group.order()?;
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let M = EcPoint::from_binary(&group, &MATTER_M_BIN)?;
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let N = EcPoint::from_binary(&group, &MATTER_N_BIN)?;
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Ok(Self {
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group,
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order,
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xy: Mpi::new(0)?,
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M,
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N,
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w0: Mpi::new(0)?,
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w1: Mpi::new(0)?,
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L: EcPoint::new()?,
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pB: EcPoint::new()?,
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})
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}
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// Computes w0 from w0s respectively
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2023-02-02 18:22:21 +00:00
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pub fn set_w0_from_w0s(&mut self, w0s: &[u8]) -> Result<(), Error> {
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// From the Matter Spec,
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// w0 = w0s mod p
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// where p is the order of the curve
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self.w0 = Mpi::from_binary(w0s)?;
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self.w0 = self.w0.modulo(&self.order)?;
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Ok(())
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}
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2023-02-02 18:22:21 +00:00
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pub fn set_w1_from_w1s(&mut self, w1s: &[u8]) -> Result<(), Error> {
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// From the Matter Spec,
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// w1 = w1s mod p
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// where p is the order of the curve
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self.w1 = Mpi::from_binary(w1s)?;
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self.w1 = self.w1.modulo(&self.order)?;
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Ok(())
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}
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2023-02-02 18:22:21 +00:00
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pub fn set_w0(&mut self, w0: &[u8]) -> Result<(), Error> {
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2022-12-27 09:32:52 +05:30
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self.w0 = Mpi::from_binary(w0)?;
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Ok(())
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}
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2023-02-02 18:22:21 +00:00
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pub fn set_w1(&mut self, w1: &[u8]) -> Result<(), Error> {
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2022-12-27 09:32:52 +05:30
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self.w1 = Mpi::from_binary(w1)?;
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Ok(())
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}
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2023-02-02 18:22:21 +00:00
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#[allow(non_snake_case)]
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pub fn set_L(&mut self, l: &[u8]) -> Result<(), Error> {
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2023-01-11 13:35:25 +01:00
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self.L = EcPoint::from_binary(&self.group, l)?;
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2023-01-08 12:27:27 +05:30
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Ok(())
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}
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2022-12-27 09:32:52 +05:30
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#[allow(non_snake_case)]
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#[allow(dead_code)]
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2023-02-02 18:22:21 +00:00
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pub fn set_L_from_w1s(&mut self, w1s: &[u8]) -> Result<(), Error> {
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2022-12-27 09:32:52 +05:30
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// From the Matter spec,
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// L = w1 * P
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// where P is the generator of the underlying elliptic curve
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self.set_w1_from_w1s(w1s)?;
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// TODO: rust-mbedtls doesn't yet accept the DRBG parameter
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self.L = self.group.generator()?.mul(&mut self.group, &self.w1)?;
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Ok(())
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}
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#[allow(non_snake_case)]
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2023-02-02 18:22:21 +00:00
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pub fn get_pB(&mut self, pB: &mut [u8]) -> Result<(), Error> {
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2022-12-27 09:32:52 +05:30
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// From the SPAKE2+ spec (https://datatracker.ietf.org/doc/draft-bar-cfrg-spake2plus/)
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// for y
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// - select random y between 0 to p
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// - Y = y*P + w0*N
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// - pB = Y
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// A private key on this curve is a random number between 0 to p
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let mut ctr_drbg = CtrDrbg::new(Arc::new(OsEntropy::new()), None)?;
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self.xy = Pk::generate_ec(&mut ctr_drbg, EcGroupId::SecP256R1)?.ec_private()?;
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let P = self.group.generator()?;
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self.pB = EcPoint::muladd(&mut self.group, &P, &self.xy, &self.N, &self.w0)?;
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let pB_internal = self.pB.to_binary(&self.group, false)?;
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let pB_internal = pB_internal.as_slice();
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if pB_internal.len() != pB.len() {
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error!("pB length mismatch");
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return Err(Error::Invalid);
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}
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pB.copy_from_slice(pB_internal);
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Ok(())
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}
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#[allow(non_snake_case)]
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2023-02-02 18:22:21 +00:00
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pub fn get_TT_as_verifier(
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&mut self,
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context: &[u8],
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pA: &[u8],
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pB: &[u8],
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out: &mut [u8],
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) -> Result<(), Error> {
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let mut TT = Md::new(mbedtls::hash::Type::Sha256)?;
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// context
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, context)?;
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// 2 empty identifiers
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, &[])?;
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Self::add_to_tt(&mut TT, &[])?;
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2022-12-27 09:32:52 +05:30
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// M
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, &MATTER_M_BIN)?;
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2022-12-27 09:32:52 +05:30
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// N
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, &MATTER_N_BIN)?;
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2022-12-27 09:32:52 +05:30
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// X = pA
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, pA)?;
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2022-12-27 09:32:52 +05:30
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// Y = pB
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, pB)?;
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2022-12-27 09:32:52 +05:30
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let X = EcPoint::from_binary(&self.group, pA)?;
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2023-02-02 18:22:21 +00:00
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let (Z, V) = Self::get_ZV_as_verifier(
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2022-12-27 09:32:52 +05:30
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&self.w0,
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&self.L,
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&mut self.M,
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&X,
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&self.xy,
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&self.order,
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&mut self.group,
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)?;
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// Z
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let tmp = Z.to_binary(&self.group, false)?;
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let tmp = tmp.as_slice();
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, tmp)?;
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2022-12-27 09:32:52 +05:30
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// V
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let tmp = V.to_binary(&self.group, false)?;
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let tmp = tmp.as_slice();
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, tmp)?;
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2022-12-27 09:32:52 +05:30
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// w0
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let tmp = self.w0.to_binary()?;
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let tmp = tmp.as_slice();
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2023-02-02 18:22:21 +00:00
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Self::add_to_tt(&mut TT, tmp)?;
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2022-12-27 09:32:52 +05:30
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TT.finish(out)?;
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Ok(())
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}
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fn add_to_tt(tt: &mut Md, buf: &[u8]) -> Result<(), Error> {
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let mut len_buf: [u8; 8] = [0; 8];
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LittleEndian::write_u64(&mut len_buf, buf.len() as u64);
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tt.update(&len_buf)?;
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if !buf.is_empty() {
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tt.update(buf)?;
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}
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Ok(())
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}
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#[inline(always)]
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#[allow(non_snake_case)]
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#[allow(dead_code)]
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fn get_ZV_as_prover(
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w0: &Mpi,
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w1: &Mpi,
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N: &mut EcPoint,
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Y: &EcPoint,
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x: &Mpi,
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order: &Mpi,
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group: &mut EcGroup,
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) -> Result<(EcPoint, EcPoint), Error> {
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// As per the RFC, the operation here is:
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// Z = h*x*(Y - w0*N)
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// V = h*w1*(Y - w0*N)
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// We will follow the same sequence as in C++ SDK, under the assumption
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// that the same sequence works for all embedded platforms. So the step
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// of operations is:
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// tmp = x*w0
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// Z = x*Y + tmp*N (N is inverted to get the 'negative' effect)
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// Z = h*Z (cofactor Mul)
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let mut tmp = x.mul(w0)?;
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tmp = tmp.modulo(order)?;
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2023-02-02 18:22:21 +00:00
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let inverted_N = Self::invert(group, N)?;
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let Z = EcPoint::muladd(group, Y, x, &inverted_N, &tmp)?;
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// Cofactor for P256 is 1, so that is a No-Op
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let mut tmp = w0.mul(w1)?;
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tmp = tmp.modulo(order)?;
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let V = EcPoint::muladd(group, Y, w1, &inverted_N, &tmp)?;
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Ok((Z, V))
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}
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#[inline(always)]
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#[allow(non_snake_case)]
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#[allow(dead_code)]
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fn get_ZV_as_verifier(
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w0: &Mpi,
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L: &EcPoint,
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M: &mut EcPoint,
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X: &EcPoint,
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y: &Mpi,
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order: &Mpi,
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group: &mut EcGroup,
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) -> Result<(EcPoint, EcPoint), Error> {
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// As per the RFC, the operation here is:
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// Z = h*y*(X - w0*M)
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// V = h*y*L
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// We will follow the same sequence as in C++ SDK, under the assumption
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// that the same sequence works for all embedded platforms. So the step
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// of operations is:
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// tmp = y*w0
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// Z = y*X + tmp*M (M is inverted to get the 'negative' effect)
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// Z = h*Z (cofactor Mul)
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let mut tmp = y.mul(w0)?;
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tmp = tmp.modulo(order)?;
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2023-02-02 18:22:21 +00:00
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let inverted_M = Self::invert(group, M)?;
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let Z = EcPoint::muladd(group, X, y, &inverted_M, &tmp)?;
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// Cofactor for P256 is 1, so that is a No-Op
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let V = L.mul(group, y)?;
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Ok((Z, V))
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}
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fn invert(group: &mut EcGroup, num: &EcPoint) -> Result<EcPoint, mbedtls::Error> {
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let p = group.p()?;
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let num_y = num.y()?;
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let inverted_num_y = p.sub(&num_y)?;
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EcPoint::from_components(num.x()?, inverted_num_y)
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}
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}
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#[cfg(test)]
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mod tests {
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2023-02-02 18:22:21 +00:00
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use super::CryptoSpake2;
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2022-12-27 09:32:52 +05:30
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use crate::secure_channel::spake2p_test_vectors::test_vectors::*;
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use mbedtls::bignum::Mpi;
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use mbedtls::ecp::EcPoint;
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#[test]
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#[allow(non_snake_case)]
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fn test_get_X() {
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for t in RFC_T {
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2023-02-02 18:22:21 +00:00
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let mut c = CryptoSpake2::new().unwrap();
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2022-12-27 09:32:52 +05:30
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let x = Mpi::from_binary(&t.x).unwrap();
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c.set_w0(&t.w0).unwrap();
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let P = c.group.generator().unwrap();
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let r = EcPoint::muladd(&mut c.group, &P, &x, &c.M, &c.w0).unwrap();
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assert_eq!(t.X, r.to_binary(&c.group, false).unwrap().as_slice());
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}
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}
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#[test]
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#[allow(non_snake_case)]
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fn test_get_Y() {
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for t in RFC_T {
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2023-02-02 18:22:21 +00:00
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let mut c = CryptoSpake2::new().unwrap();
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2022-12-27 09:32:52 +05:30
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let y = Mpi::from_binary(&t.y).unwrap();
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c.set_w0(&t.w0).unwrap();
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let P = c.group.generator().unwrap();
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let r = EcPoint::muladd(&mut c.group, &P, &y, &c.N, &c.w0).unwrap();
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assert_eq!(t.Y, r.to_binary(&c.group, false).unwrap().as_slice());
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}
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}
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#[test]
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#[allow(non_snake_case)]
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fn test_get_ZV_as_prover() {
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for t in RFC_T {
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2023-02-02 18:22:21 +00:00
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let mut c = CryptoSpake2::new().unwrap();
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2022-12-27 09:32:52 +05:30
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let x = Mpi::from_binary(&t.x).unwrap();
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c.set_w0(&t.w0).unwrap();
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c.set_w1(&t.w1).unwrap();
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let Y = EcPoint::from_binary(&c.group, &t.Y).unwrap();
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2023-02-02 18:22:21 +00:00
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let (Z, V) = CryptoSpake2::get_ZV_as_prover(
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2022-12-27 09:32:52 +05:30
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&c.w0,
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&c.w1,
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&mut c.N,
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&Y,
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&x,
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&c.order,
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&mut c.group,
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)
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.unwrap();
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assert_eq!(t.Z, Z.to_binary(&c.group, false).unwrap().as_slice());
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assert_eq!(t.V, V.to_binary(&c.group, false).unwrap().as_slice());
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}
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}
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#[test]
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#[allow(non_snake_case)]
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fn test_get_ZV_as_verifier() {
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for t in RFC_T {
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2023-02-02 18:22:21 +00:00
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let mut c = CryptoSpake2::new().unwrap();
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2022-12-27 09:32:52 +05:30
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let y = Mpi::from_binary(&t.y).unwrap();
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c.set_w0(&t.w0).unwrap();
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let X = EcPoint::from_binary(&c.group, &t.X).unwrap();
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let L = EcPoint::from_binary(&c.group, &t.L).unwrap();
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2023-02-02 18:22:21 +00:00
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let (Z, V) = CryptoSpake2::get_ZV_as_verifier(
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2022-12-27 09:32:52 +05:30
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&c.w0,
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&L,
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&mut c.M,
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&X,
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&y,
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&c.order,
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&mut c.group,
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)
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.unwrap();
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assert_eq!(t.Z, Z.to_binary(&c.group, false).unwrap().as_slice());
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assert_eq!(t.V, V.to_binary(&c.group, false).unwrap().as_slice());
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}
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}
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}
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