Module x25519

Available on crate feature dep_orion only.

Diffie-Hellman key exchange over Curve25519 as specified in the RFC 7748.

Parameters:

• private_key: The private key used in key agreement.
• public_key: The public key used in key agreement.

Errors:

An error will be returned if:

• The key_agreement() operation results in an all-zero output.

Security:

• Multiple different private_key/public_key pairs can produce the same shared key. Therefore, using the resulting SharedKey, directly from key_agreement(), is not recommended. This is handled automatically in orion::kex.
• To securely generate a strong key, use PrivateKey::generate().

Recommendation:

• It is recommended to use orion::kex when possible.

Example:

use orion::hazardous::ecc::x25519::{PrivateKey, PublicKey, SharedKey, key_agreement};
use core::convert::TryFrom;

// Alice generates a private key and computes the corresponding public key
let alice_sk = PrivateKey::generate();
let alice_pk = PublicKey::try_from(&alice_sk)?;

// Bob does the same
let bob_sk = PrivateKey::generate();
let bob_pk = PublicKey::try_from(&bob_sk)?;

// They both compute a shared key using the others public key
let alice_shared = key_agreement(&alice_sk, &bob_pk)?;
let bob_shared = key_agreement(&bob_sk, &alice_pk)?;

assert_eq!(alice_shared, bob_shared);

Structs

PrivateKey

A type to represent the PrivateKey that X25519 uses.

PublicKey

A type that represents a PublicKey that X25519 uses.

SharedKey

A type to represent the SharedKey that X25519 produces.

Constants

PRIVATE_KEY_SIZE

The size of a private key used in X25519.

PUBLIC_KEY_SIZE

The size of a public key used in X25519.

SHARED_KEY_SIZE

The size of a shared key used in X25519.

Functions

key_agreement

X25519 (Diffie-Hellman with Montgomery form of Curve25519).