Struct ElligatorSwift

pub struct ElligatorSwift(/* private fields */);

Expand description

ElligatorSwift is an encoding of a uniformly chosen point on the curve as a 64-byte array that is indistinguishable from a uniformly random array. This object holds two field elements u and t, which are the inputs to the ElligatorSwift encoding function.

Implementations§

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impl ElligatorSwift

pub fn new(secret_key: SecretKey, rand: [u8; 32]) -> ElligatorSwift

Create a new ElligatorSwift object from a 64-byte array.

pub fn from_array(ellswift: [u8; 64]) -> ElligatorSwift

Creates an ElligatorSwift object from a 64-byte array.

pub fn to_array(&self) -> [u8; 64]

Returns the 64-byte array representation of this ElligatorSwift object.

pub fn from_seckey<C>( secp: &Secp256k1<C>, sk: SecretKey, aux_rand: Option<[u8; 32]>, ) -> ElligatorSwift
where C: Verification,

Creates the Elligator Swift encoding from a secret key, using some aux_rand if defined. This method is preferred instead of just decoding, because the private key offers extra entropy.

§Example

    use secp256k1::{ellswift::ElligatorSwift, PublicKey, Secp256k1, SecretKey};
    let secp = Secp256k1::new();
    let sk = SecretKey::from_slice(&[1; 32]).unwrap();
    let es = ElligatorSwift::from_seckey(&secp, sk, None);

pub fn from_pubkey(pk: PublicKey) -> ElligatorSwift

Computes the ElligatorSwift encoding for a valid public key

§Example

    use secp256k1::{ellswift::ElligatorSwift, PublicKey, Secp256k1, SecretKey};
    let secp = Secp256k1::new();
    let sk = SecretKey::from_slice(&[1; 32]).unwrap();
    let pk = PublicKey::from_secret_key(&secp, &sk);
    let es = ElligatorSwift::from_pubkey(pk);

pub fn shared_secret( ellswift_a: ElligatorSwift, ellswift_b: ElligatorSwift, secret_key: SecretKey, party: ElligatorSwiftParty, data: Option<&[u8]>, ) -> ElligatorSwiftSharedSecret

Computes a shared secret only known by Alice and Bob. This is obtained by computing the x-only Elliptic Curve Diffie-Hellman (ECDH) shared secret between Alice and Bob.

§Example

    use secp256k1::{
        ellswift::{ElligatorSwift, ElligatorSwiftParty},
        PublicKey, SecretKey, XOnlyPublicKey, Secp256k1,
    };
    use core::str::FromStr;

    let secp = Secp256k1::new();

    let alice_sk = SecretKey::from_str("e714e76bdd67ad9f495683c37934148f4efc25ce3f01652c8a906498339e1f3a").unwrap();
    let bob_sk = SecretKey::from_str("b6c4b0e2f8c4359caf356a618cd1649d18790a1d67f7c2d1e4760e04c785db4f").unwrap();

    let alice_es = ElligatorSwift::from_seckey(&secp, alice_sk, None);
    let bob_es = ElligatorSwift::from_seckey(&secp, bob_sk, None);

    let alice_shared_secret = ElligatorSwift::shared_secret(alice_es, bob_es, alice_sk, ElligatorSwiftParty::A, None);
    let bob_shared_secret = ElligatorSwift::shared_secret(alice_es, bob_es, bob_sk, ElligatorSwiftParty::B, None);

    assert_eq!(alice_shared_secret, bob_shared_secret);

pub fn shared_secret_with_hasher<F>( ellswift_a: ElligatorSwift, ellswift_b: ElligatorSwift, secret_key: SecretKey, party: ElligatorSwiftParty, hash_function: F, ) -> ElligatorSwiftSharedSecret
where F: FnMut([u8; 32], [u8; 64], [u8; 64]) -> ElligatorSwiftSharedSecret,

Computes a shared secret, just like shared_secret, but with a custom hash function for computing the shared secret. For compatibility with other libraries, you should use shared_secret instead, which is already compatible with BIP324. The hash function takes three arguments: the shared point, and the ElligatorSwift encodings of the two parties and returns a 32-byte shared secret.