Struct rubedo::crypto::VerifyingKey

pub struct VerifyingKey { /* private fields */ }

An ed25519 verifying key which can be used to produce signatures.

This is a wrapper around ed25519_dalek::VerifyingKey, which provides additional functionality, including serialisation and deserialisation using Serde, via the implementation of the ByteSized and ByteSizedFull traits.

See also

• ed25519_dalek::VerifyingKey

Implementations

impl VerifyingKey

pub const fn into_inner(self) -> RealVerifyingKey

Consumes the VerifyingKey and returns the inner ed25519_dalek::VerifyingKey.

Methods from Deref<Target = RealVerifyingKey>

pub fn to_bytes(&self) -> [u8; 32]

Convert this public key to a byte array.

pub fn as_bytes(&self) -> &[u8; 32]

View this public key as a byte array.

pub fn is_weak(&self) -> bool

Returns whether this is a weak public key, i.e., if this public key has low order.

A weak public key can be used to generate a signature that’s valid for almost every message. Self::verify_strict denies weak keys, but if you want to check for this property before verification, then use this method.

pub fn verify_strict( &self, message: &[u8], signature: &Signature ) -> Result<(), Error>

Strictly verify a signature on a message with this keypair’s public key.

On The (Multiple) Sources of Malleability in Ed25519 Signatures

This version of verification is technically non-RFC8032 compliant. The following explains why.

1. Scalar Malleability

The authors of the RFC explicitly stated that verification of an ed25519 signature must fail if the scalar s is not properly reduced mod $\ell$:

To verify a signature on a message M using public key A, with F being 0 for Ed25519ctx, 1 for Ed25519ph, and if Ed25519ctx or Ed25519ph is being used, C being the context, first split the signature into two 32-octet halves. Decode the first half as a point R, and the second half as an integer S, in the range 0 <= s < L. Decode the public key A as point A’. If any of the decodings fail (including S being out of range), the signature is invalid.)

All verify_*() functions within ed25519-dalek perform this check.

2. Point malleability

The authors of the RFC added in a malleability check to step #3 in §5.1.7, for small torsion components in the R value of the signature, which is not strictly required, as they state:

Check the group equation [8][S]B = [8]R + [8][k]A’. It’s sufficient, but not required, to instead check [S]B = R + [k]A’.

History of Malleability Checks

As originally defined (cf. the “Malleability” section in the README of this repo), ed25519 signatures didn’t consider any form of malleability to be an issue. Later the scalar malleability was considered important. Still later, particularly with interests in cryptocurrency design and in unique identities (e.g. for Signal users, Tor onion services, etc.), the group element malleability became a concern.

However, libraries had already been created to conform to the original definition. One well-used library in particular even implemented the group element malleability check, but only for batch verification! Which meant that even using the same library, a single signature could verify fine individually, but suddenly, when verifying it with a bunch of other signatures, the whole batch would fail!

“Strict” Verification

This method performs both of the above signature malleability checks.

It must be done as a separate method because one doesn’t simply get to change the definition of a cryptographic primitive ten years after-the-fact with zero consideration for backwards compatibility in hardware and protocols which have it already have the older definition baked in.

Return

Returns Ok(()) if the signature is valid, and Err otherwise.

pub fn to_montgomery(&self) -> MontgomeryPoint

Convert this verifying key into Montgomery form.

This can be used for performing X25519 Diffie-Hellman using Ed25519 keys. The output of this function is a valid X25519 public key whose secret key is sk.to_scalar_bytes(), where sk is a valid signing key for this VerifyingKey.

Note

We do NOT recommend this usage of a signing/verifying key. Signing keys are usually long-term keys, while keys used for key exchange should rather be ephemeral. If you can help it, use a separate key for encryption.

For more information on the security of systems which use the same keys for both signing and Diffie-Hellman, see the paper On using the same key pair for Ed25519 and an X25519 based KEM.

Trait Implementations

impl AsRef<[u8; 32]> for VerifyingKey

fn as_ref(&self) -> &[u8; 32]

Converts this type into a shared reference of the (usually inferred) input type.

impl ByteSized<32> for VerifyingKey

fn from_bytes(bytes: [u8; 32]) -> Self

Converts a [u8; 32] to a VerifyingKey.

Note that this is a direct conversion, and does not check the validity of the bytes. If the bytes are not a valid verifying key, the key will be created as empty. To check the validity of the bytes, use VerifyingKey::from_bytes() instead.

fn as_bytes(&self) -> &[u8; 32]

Returns a byte slice of the container’s contents.

fn to_bytes(&self) -> [u8; 32]

Returns a copy of the container data as a fixed-length array of bytes.

fn to_base64(&self) -> String

Returns the container data converted to a base64-encoded String.

fn from_base64(encoded: &str) -> Result<Self, DecodeError>

Converts a base64-encoded String to a ByteSized type.

fn to_hex(&self) -> String

Returns the container data converted to a hex-encoded String.

fn from_hex(encoded: &str) -> Result<Self, FromHexError>

Converts a hex-encoded String to a ByteSized.

fn to_vec(&self) -> Vec<u8>

Returns a copy of the container data converted to a vector of bytes.

impl Clone for VerifyingKey

fn clone(&self) -> VerifyingKey

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for VerifyingKey

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for VerifyingKey

fn default() -> Self

Returns the “default value” for a type.

impl Deref for VerifyingKey

type Target = VerifyingKey

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<'de> Deserialize<'de> for VerifyingKey

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialises the verifying key from a String.

This method deserialises the verifying key from hexadecimal string representation.

See also

• VerifyingKey::deserialize()
• VerifyingKey::from_base64()

impl Display for VerifyingKey

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the verifying key for display.

This method serialises the verifying key into hexadecimal string representation.

See also

• VerifyingKey::serialize()
• VerifyingKey::to_base64()

impl ForceFrom<&[u8]> for VerifyingKey

fn force_from(b: &[u8]) -> Self

Converts a &[u8] to a VerifyingKey.

Note that if the incoming [u8] is too long to fit, it will be truncated without error or warning. If there is not enough data, it will be padded with zeroes. If this situation needs checking, use try_from() instead.

impl<const N: usize> ForceFrom<&[u8; N]> for VerifyingKey

fn force_from(b: &[u8; N]) -> Self

Converts a &[u8; N] to a VerifyingKey.

Note that if the incoming [u8; N] is too long to fit, it will be truncated without error or warning. If there is not enough data, it will be padded with zeroes. If this situation needs checking, use try_from() instead.

impl ForceFrom<&Vec<u8>> for VerifyingKey

fn force_from(v: &Vec<u8>) -> Self

Converts a &Vec[u8] to a VerifyingKey.

Note that if the incoming Vec<u8> is too long to fit, it will be truncated without error or warning. If there is not enough data, it will be padded with zeroes. If this situation needs checking, use try_from() instead.

impl ForceFrom<Vec<u8>> for VerifyingKey

fn force_from(v: Vec<u8>) -> Self

Converts a Vec<u8> to a VerifyingKey.

Note that if the incoming Vec<u8> is too long to fit, it will be truncated without error or warning. If there is not enough data, it will be padded with zeroes. If this situation needs checking, use try_from() instead.

impl From<&[u8; 32]> for VerifyingKey

fn from(b: &[u8; 32]) -> Self

Converts a &[u8; 32] to a VerifyingKey.

impl From<&VerifyingKey> for VerifyingKey

fn from(key: &RealVerifyingKey) -> Self

Converts a &ed25519_dalek::VerifyingKey to a VerifyingKey.

impl From<[u8; 32]> for VerifyingKey

fn from(b: [u8; 32]) -> Self

Converts a [u8; 32] to a VerifyingKey.

impl From<VerifyingKey> for VerifyingKey

fn from(key: RealVerifyingKey) -> Self

Converts a ed25519_dalek::VerifyingKey to a VerifyingKey.

impl FromStr for VerifyingKey

type Err = ByteSizedError

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<Self, Self::Err>

Parses a string s to return a value of this type.

impl Hash for VerifyingKey

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for VerifyingKey

fn eq(&self, other: &VerifyingKey) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for VerifyingKey

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialises the verifying key to a String.

This method serialises the verifying key into hexadecimal string representation.

See also

• VerifyingKey::deserialize()
• VerifyingKey::<Display>fmt()
• VerifyingKey::to_base64()

impl TryFrom<&[u8]> for VerifyingKey

fn try_from(b: &[u8]) -> Result<Self, Self::Error>

Converts a &[u8] to a VerifyingKey.

type Error = ByteSizedError

The type returned in the event of a conversion error.

impl TryFrom<&String> for VerifyingKey

fn try_from(s: &String) -> Result<Self, Self::Error>

Converts a &String to a VerifyingKey.

type Error = ByteSizedError

The type returned in the event of a conversion error.

impl TryFrom<&Vec<u8>> for VerifyingKey

fn try_from(v: &Vec<u8>) -> Result<Self, Self::Error>

Converts a &Vec[u8] to a VerifyingKey.

type Error = ByteSizedError

The type returned in the event of a conversion error.

impl TryFrom<&str> for VerifyingKey

fn try_from(s: &str) -> Result<Self, Self::Error>

Converts a &str to a VerifyingKey.

type Error = ByteSizedError

The type returned in the event of a conversion error.

impl TryFrom<Box<str>> for VerifyingKey

fn try_from(s: Box<str>) -> Result<Self, Self::Error>

Converts a boxed string slice to a VerifyingKey.

type Error = ByteSizedError

The type returned in the event of a conversion error.

impl<'a> TryFrom<Cow<'a, str>> for VerifyingKey

fn try_from(s: Cow<'a, str>) -> Result<Self, Self::Error>

Converts a clone-on-write string to a VerifyingKey.

type Error = ByteSizedError

The type returned in the event of a conversion error.

impl TryFrom<String> for VerifyingKey

fn try_from(s: String) -> Result<Self, Self::Error>

Converts a String to a VerifyingKey.

type Error = ByteSizedError

The type returned in the event of a conversion error.

impl TryFrom<Vec<u8>> for VerifyingKey

fn try_from(v: Vec<u8>) -> Result<Self, Self::Error>

Converts a Vec<u8> to a VerifyingKey.

type Error = ByteSizedError

The type returned in the event of a conversion error.

impl ByteSizedFull<32> for VerifyingKey

impl Copy for VerifyingKey

impl Eq for VerifyingKey

impl StructuralPartialEq for VerifyingKey