# Crate x25519_dalek[−][src]

x25519 Diffie-Hellman key exchange

A pure-Rust implementation of x25519 elliptic curve Diffie-Hellman key exchange as specified by Mike Hamburg and Adam Langley in RFC7748.

# Examples

"Secret Messages" cover image and zine copyright © Amy Wibowo (@sailorhg)

Alice and Bob are two adorable kittens who have lost their mittens, and they wish to be able to send secret messages to each other to coordinate finding them, otherwise—if their caretaker cat finds out—they will surely be called naughty kittens and be given no pie!

But the two kittens are quite clever. Even though their paws are still too
big and the rest of them is 90% fuzziness, these clever kittens have been
studying up on modern public key cryptography and have learned a nifty trick
called *elliptic curve Diffie-Hellman key exchange*. With the right
incantations, the kittens will be able to secretly organise to find their
mittens, and then spend the rest of the afternoon nomming some yummy pie!

First, Alice uses `x25519_dalek::generate_secret()`

and
`x25519_dalek::generate_public()`

to produce her secret and public keys:

extern crate x25519_dalek; extern crate rand; use x25519_dalek::generate_secret; use x25519_dalek::generate_public; use rand::thread_rng; let mut alice_csprng = thread_rng(); let alice_secret = generate_secret(&mut alice_csprng); let alice_public = generate_public(&alice_secret);

Bob does the same:

let mut bob_csprng = thread_rng(); let bob_secret = generate_secret(&mut bob_csprng); let bob_public = generate_public(&bob_secret);

Alice meows across the room, telling `alice_public`

to Bob, and Bob
loudly meows `bob_public`

back to Alice. Alice now computes her
shared secret with Bob by doing:

use x25519_dalek::diffie_hellman; let shared_secret = diffie_hellman(&alice_secret, &bob_public.as_bytes());

Similarly, Bob computes the same shared secret by doing:

let shared_secret = diffie_hellman(&bob_secret, &alice_public.as_bytes());

Voilá! Alice and Bob can now use their shared secret to encrypt their meows, for example, by using it to generate a key and nonce for an authenticated-encryption cipher.

## Functions

diffie_hellman |
Utility function to make it easier to call |

generate_public |
Given an x25519 secret key, compute its corresponding public key. |

generate_secret |
Generate an x25519 secret key. |

x25519 |
The x25519 function, as specified in RFC7748. |