package x448

import "github.com/cloudflare/circl/dh/x448"

Package x448 provides Diffie-Hellman functions as specified in RFC-7748.

Validation of public keys.

The Diffie-Hellman function, as described in RFC-7748 [1], works for any public key. However, if a different protocol requires contributory behaviour [2,3], then the public keys must be validated against low-order points [3,4]. To do that, the Shared function performs this validation internally and returns false when the public key is invalid (i.e., it is a low-order point).

References:

• [1] RFC7748 by Langley, Hamburg, Turner (https://rfc-editor.org/rfc/rfc7748.txt)
• [2] Curve25519 by Bernstein (https://cr.yp.to/ecdh.html)
• [3] Bernstein (https://cr.yp.to/ecdh.html#validate)
• [4] Cremers&Jackson (https://eprint.iacr.org/2019/526)

{
	var AliceSecret, BobSecret,
		AlicePublic, BobPublic,
		AliceShared, BobShared Key

	// Generating Alice's secret and public keys
	_, _ = io.ReadFull(rand.Reader, AliceSecret[:])
	KeyGen(&AlicePublic, &AliceSecret)

	// Generating Bob's secret and public keys
	_, _ = io.ReadFull(rand.Reader, BobSecret[:])
	KeyGen(&BobPublic, &BobSecret)

	// Deriving Alice's shared key
	okA := Shared(&AliceShared, &AliceSecret, &BobPublic)

	// Deriving Bob's shared key
	okB := Shared(&BobShared, &BobSecret, &AlicePublic)

	fmt.Println(AliceShared == BobShared && okA && okB)
	// Output: true
}

true

Index ¶

• Constants
• func KeyGen(public, secret *Key)
• func Shared(shared, secret, public *Key) bool
• type Key

Examples ¶

• package (X448)

Constants ¶

const Size = 56

Size is the length in bytes of a X448 key.

Functions ¶

func KeyGen ¶

func KeyGen(public, secret *Key)

KeyGen obtains a public key given a secret key.

func Shared ¶

func Shared(shared, secret, public *Key) bool

Shared calculates Alice's shared key from Alice's secret key and Bob's public key returning true on success. A failure case happens when the public key is a low-order point, thus the shared key is all-zeros and the function returns false.

Types ¶

type Key ¶

type Key [Size]byte

Key represents a X448 key.

Source Files ¶

curve.go curve_amd64.go curve_generic.go doc.go key.go table.go