package fiat-p256

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Module type
Class type
type error = [
  1. | `Invalid_range
  2. | `Invalid_format
  3. | `Invalid_length
  4. | `Not_on_curve
  5. | `At_infinity

The type for public key parsing errors.

val pp_error : Stdlib.Format.formatter -> error -> unit

Pretty printer for public key parsing errors

type secret

Type for P256 private keys

val gen_key : rng:(int -> Cstruct.t) -> secret * Cstruct.t

gen_key ~rng generates a private and a public key for Ephemeral Diffie-Hellman over P256. The returned key pair MUST only be used for a single key exchange.

rng is the function used to repeteadly generate a private key until a valid candidate is obtained. rng's int parameter is the size of the Cstruct.t to generate. If rng returns an invalid length buffer, Failure _ is raised.

The generated private key is checked to be greater than zero and lower than the group order meaning the public key cannot be the point at inifinity.

val key_exchange : secret -> Cstruct.t -> (Cstruct.t, error) Stdlib.result

key_exchange secret received_public_key performs Diffie-Hellman key exchange using your secret and the data received from the other party. Returns the shared secret or an error if the received data is wrongly encoded, doesn't represent a point on the curve or represent the point at infinity.

The shared secret is returned as is i.e. not stripped from leading 0x00 bytes.


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