# init(recipientKey:ciphersuite:info:authenticatedBy:presharedKey:presharedKeyIdentifier:) Creates a sender in authentication and preshared key mode. ``` init(recipientKey: SK.PublicKey, ciphersuite: HPKE.Ciphersuite, info: Data, authenticatedBy authenticationKey: SK, presharedKey psk: SymmetricKey, presharedKeyIdentifier pskID: Data) throws where SK : HPKEDiffieHellmanPrivateKey ``` ## Parameters `recipientKey` The recipient’s public key for encrypting the messages. `ciphersuite` The cipher suite that defines the cryptographic algorithms to use. `info` Data that the key derivation function uses to compute the symmetric key material. The sender and the recipient need to use the same `info` data. `authenticationKey` The sender’s private key for generating the HMAC. `psk` A preshared key (PSK) that the sender and the recipient both hold. `pskID` An identifier for the PSK. ## Discussion The `Sender` encrypts messages in authentication and preshared key (`auth_psk`) mode using a symmetric encryption key that the sender and recipient both know in advance, in combination with a key it derives using a key derivation function (KDF) and the key schedule data in `info`. Messages also include authentication data so that the recipient can verify the authenticity of the sender’s private key. > Note: The system throws errors from ``doc://com.apple.CryptoKit/documentation/CryptoKit/HPKE/Errors`` when it encounters them. --- 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)