EncryptWithRefKey.swift

let algorithm: SecKeyAlgorithm = .eciesEncryptionStandardX963SHA1AESGCM

func encrypt(with key: String, string: String) -> String? {
    var error: Unmanaged<CFError>?

    let attributes: [String: Any] = [
        kSecAttrKeyClass as String: kSecAttrKeyClassPublic,
        kSecAttrKeyType as String: kSecAttrKeyTypeECSECPrimeRandom,
        kSecAttrKeySizeInBits as String: 256]

    guard let dataKey = Data(base64Encoded: key, options: .ignoreUnknownCharacters),
          let pubKey = SecKeyCreateWithData(dataKey as CFData, attributes as CFDictionary, &error) else { return nil }

    guard let data = string.data(using: .utf8),
          let encrypted = SecKeyCreateEncryptedData(pubKey, algorithm, data as CFData, &error) { return nil }
    return (encrypted as Data).base64EncodedString()
}