# HPKEPublicKeySerialization Implementations ## Topics ### Initializers [`init(D, kem: HPKE.KEM) throws`](/documentation/CryptoKit/P521/KeyAgreement/PublicKey/init(_:kem:)) Creates a NIST P-521 elliptic curve public key for use with Diffie-Hellman key exchange. ### Instance Methods [`func hpkeRepresentation(kem: HPKE.KEM) throws -> Data`](/documentation/CryptoKit/P521/KeyAgreement/PublicKey/hpkeRepresentation(kem:)) Creates a serialized representation of the public key. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)