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Derive Hash for a bunch of types #663

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4 changes: 2 additions & 2 deletions src/modular/boxed_monty_form.rs
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Expand Up @@ -20,7 +20,7 @@ use zeroize::Zeroize;

/// Parameters to efficiently go to/from the Montgomery form for an odd modulus whose size and value
/// are both chosen at runtime.
#[derive(Clone, Debug, Eq, PartialEq)]
#[derive(Clone, Debug, Eq, PartialEq, Hash)]
pub struct BoxedMontyParams {
/// The constant modulus
modulus: Odd<BoxedUint>,
Expand Down Expand Up @@ -115,7 +115,7 @@ impl BoxedMontyParams {
}

/// An integer in Montgomery form represented using heap-allocated limbs.
#[derive(Clone, Debug, Eq, PartialEq)]
#[derive(Clone, Debug, Eq, PartialEq, Hash)]
pub struct BoxedMontyForm {
/// Value in the Montgomery form.
montgomery_form: BoxedUint,
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2 changes: 1 addition & 1 deletion src/modular/boxed_monty_form/inv.rs
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Expand Up @@ -37,7 +37,7 @@ impl PrecomputeInverter for BoxedMontyParams {
}
}

/// Bernstein-Yang inverter which inverts [`DynResidue`] types.
/// Bernstein-Yang inverter which inverts [`MontyForm`] types.
pub struct BoxedMontyFormInverter {
/// Precomputed Bernstein-Yang inverter.
inverter: BoxedSafeGcdInverter,
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2 changes: 1 addition & 1 deletion src/modular/const_monty_form.rs
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Expand Up @@ -68,7 +68,7 @@ pub trait ConstMontyParams<const LIMBS: usize>:
/// The modulus is constant, so it cannot be set at runtime.
///
/// Internally, the value is stored in Montgomery form (multiplied by MOD::ONE) until it is retrieved.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
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@tarcieri tarcieri Aug 25, 2024 •
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I'm a little concerned about deriving Hash for potentially secret-containing types. Though the default Hasher is SipHash which is fine when properly keyed, other hashers do not necessarily prevent preimage attacks

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Do you think documenting the caveats properly is enough? A bigint library that blocks all potential security misuses risks crippling itself a fair bit and it’s not obvious where to draw the line. I’d argue that in this case it’s expected that users know about the security hazards.

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It would definitely need documentation. This library is documented as being constant-time by default and we are careful to treat each integer as potentially containing a secret, with separate *_vartime methods which act in variable-time so as to make those sort of secret accesses easier to audit.

I would also want to know what a use case is for keying a HashMap with ConstMontyForm.

pub struct ConstMontyForm<MOD: ConstMontyParams<LIMBS>, const LIMBS: usize> {
montgomery_form: Uint<LIMBS>,
phantom: PhantomData<MOD>,
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4 changes: 2 additions & 2 deletions src/modular/monty_form.rs
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Expand Up @@ -17,7 +17,7 @@ use crate::{Concat, Limb, Monty, NonZero, Odd, Split, Uint, Word};
use subtle::{Choice, ConditionallySelectable, ConstantTimeEq};

/// Parameters to efficiently go to/from the Montgomery form for an odd modulus provided at runtime.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct MontyParams<const LIMBS: usize> {
/// The constant modulus
modulus: Odd<Uint<LIMBS>>,
Expand Down Expand Up @@ -145,7 +145,7 @@ impl<const LIMBS: usize> ConstantTimeEq for MontyParams<LIMBS> {

/// An integer in Montgomery form represented using `LIMBS` limbs.
/// The odd modulus is set at runtime.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
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Ditto here re: potentially secret-containing types

pub struct MontyForm<const LIMBS: usize> {
montgomery_form: Uint<LIMBS>,
params: MontyParams<LIMBS>,
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2 changes: 1 addition & 1 deletion src/uint/div_limb.rs
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Expand Up @@ -187,7 +187,7 @@ pub(crate) const fn div3by2(
}

/// A pre-calculated reciprocal for division by a single limb.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub struct Reciprocal {
divisor_normalized: Word,
shift: u32,
Expand Down
2 changes: 1 addition & 1 deletion src/wrapping.rs
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Expand Up @@ -17,7 +17,7 @@ use serdect::serde::{Deserialize, Deserializer, Serialize, Serializer};
///
/// This is analogous to [`core::num::Wrapping`] but allows this crate to
/// define trait impls for this type.
#[derive(Copy, Clone, Debug, Default, Eq, PartialEq, PartialOrd, Ord)]
#[derive(Copy, Clone, Debug, Default, Eq, PartialEq, PartialOrd, Ord, Hash)]
pub struct Wrapping<T>(pub T);

impl<T: WrappingAdd> Add<Self> for Wrapping<T> {
Expand Down