Trait frost_core::Ciphersuite

pub trait Ciphersuite: Copy + Clone + PartialEq + Debug {
    type Group: Group;
    type HashOutput: AsRef<[u8]>;
    type SignatureSerialization: AsRef<[u8]> + TryFrom<Vec<u8>>;

    const ID: &'static str;

    // Required methods
    fn H1(m: &[u8]) -> <<Self::Group as Group>::Field as Field>::Scalar;
    fn H2(m: &[u8]) -> <<Self::Group as Group>::Field as Field>::Scalar;
    fn H3(m: &[u8]) -> <<Self::Group as Group>::Field as Field>::Scalar;
    fn H4(m: &[u8]) -> Self::HashOutput;
    fn H5(m: &[u8]) -> Self::HashOutput;

    // Provided methods
    fn HDKG(
        _m: &[u8]
    ) -> Option<<<Self::Group as Group>::Field as Field>::Scalar> { ... }
    fn HID(
        _m: &[u8]
    ) -> Option<<<Self::Group as Group>::Field as Field>::Scalar> { ... }
    fn verify_signature(
        msg: &[u8],
        signature: &Signature<Self>,
        public_key: &VerifyingKey<Self>
    ) -> Result<(), Error<Self>> { ... }
}

A FROST ciphersuite specifies the underlying prime-order group details and cryptographic hash function.

Required Associated Types

type Group: Group

The prime order group (or subgroup) that this ciphersuite operates over.

type HashOutput: AsRef<[u8]>

A unique byte array of fixed length.

type SignatureSerialization: AsRef<[u8]> + TryFrom<Vec<u8>>

A unique byte array of fixed length that is the Group::ElementSerialization + Group::ScalarSerialization

Required Associated Constants

const ID: &'static str

The ciphersuite ID string

Required Methods

fn H1(m: &[u8]) -> <<Self::Group as Group>::Field as Field>::Scalar

H1 for a FROST ciphersuite.

Maps arbitrary inputs to Self::Scalar elements of the prime-order group scalar field.

fn H2(m: &[u8]) -> <<Self::Group as Group>::Field as Field>::Scalar

H2 for a FROST ciphersuite.

Maps arbitrary inputs to Self::Scalar elements of the prime-order group scalar field.

fn H3(m: &[u8]) -> <<Self::Group as Group>::Field as Field>::Scalar

H3 for a FROST ciphersuite.

Maps arbitrary inputs to Self::Scalar elements of the prime-order group scalar field.

fn H4(m: &[u8]) -> Self::HashOutput

H4 for a FROST ciphersuite.

Usually an an alias for the ciphersuite hash function H with domain separation applied.

fn H5(m: &[u8]) -> Self::HashOutput

H5 for a FROST ciphersuite.

Usually an an alias for the ciphersuite hash function H with domain separation applied.

Provided Methods

fn HDKG(_m: &[u8]) -> Option<<<Self::Group as Group>::Field as Field>::Scalar>

Hash function for a FROST ciphersuite, used for the DKG.

The DKG it not part of the specification, thus this is optional. It can return None if DKG is not supported by the Ciphersuite. This is the default implementation.

Maps arbitrary inputs to non-zero Self::Scalar elements of the prime-order group scalar field.

fn HID(_m: &[u8]) -> Option<<<Self::Group as Group>::Field as Field>::Scalar>

Hash function for a FROST ciphersuite, used for deriving identifiers from strings.

This feature is not part of the specification and is just a convenient way of creating identifiers. Therefore it can return None if this is not supported by the Ciphersuite. This is the default implementation.

Maps arbitrary inputs to non-zero Self::Scalar elements of the prime-order group scalar field.

fn verify_signature( msg: &[u8], signature: &Signature<Self>, public_key: &VerifyingKey<Self> ) -> Result<(), Error<Self>>

Verify a signature for this ciphersuite. The default implementation uses the “cofactored” equation (it multiplies by the cofactor returned by Group::cofactor()).

Cryptographic Safety

You may override this to provide a tailored implementation, but if the ciphersuite defines it, it must also multiply by the cofactor to comply with the RFC. Note that batch verification (see crate::batch::Verifier) also uses the default implementation regardless whether a tailored implementation was provided.

Implementors