cryptography-core/dev.whyoleg.cryptography.algorithms/XDH

XDH

@SubclassOptInRequired(markerClass = [CryptographyProviderApi::class])

interface XDH : CryptographyAlgorithm(source)

X25519/X448 Diffie-Hellman key agreement as defined in RFC 7748.

XDH allows two parties to establish a shared secret over an insecure channel using modern Montgomery curves. It is the recommended alternative to ECDH for new applications, offering simpler implementation and resistance to timing attacks.

val aliceKeys = provider.get(XDH).keyPairGenerator(XDH.Curve.X25519).generateKey()
val bobKeys = provider.get(XDH).keyPairGenerator(XDH.Curve.X25519).generateKey()
val sharedSecret = aliceKeys.privateKey.sharedSecretGenerator().generateSharedSecret(bobKeys.publicKey)

The raw shared secret output should not be used directly as a key. Use a key derivation function like HKDF to derive actual keys from the shared secret.

For key agreement using Weierstrass curves, see ECDH.

Types

Companion

object Companion : CryptographyAlgorithmId<XDH>

Curve

enum Curve : Enum<XDH.Curve>

Supported XDH curves.

KeyPair

@SubclassOptInRequired(markerClass = [CryptographyProviderApi::class])

interface KeyPair

PrivateKey

@SubclassOptInRequired(markerClass = [CryptographyProviderApi::class])

interface PrivateKey : Encodable<XDH.PrivateKey.Format> , PublicKeyAccessor<XDH.PublicKey>

An XDH private key that provides shared secret computation via sharedSecretGenerator.

PublicKey

@SubclassOptInRequired(markerClass = [CryptographyProviderApi::class])

interface PublicKey : Encodable<XDH.PublicKey.Format>

An XDH public key that provides shared secret computation via sharedSecretGenerator.

Properties

open override val id: CryptographyAlgorithmId<XDH>

The typed identifier that uniquely distinguishes this algorithm and is used to look it up from a CryptographyProvider.

Functions

keyPairGenerator

abstract fun keyPairGenerator(curve: XDH.Curve): KeyGenerator<XDH.KeyPair>

Returns a KeyGenerator that generates XDH key pairs on the given curve.

privateKeyDecoder

abstract fun privateKeyDecoder(curve: XDH.Curve): Decoder<XDH.PrivateKey.Format, XDH.PrivateKey>

Returns a Decoder that decodes XDH private keys on the given curve from the specified PrivateKey.Format.

publicKeyDecoder

abstract fun publicKeyDecoder(curve: XDH.Curve): Decoder<XDH.PublicKey.Format, XDH.PublicKey>

Returns a Decoder that decodes XDH public keys on the given curve from the specified PublicKey.Format.