CryptoKitExample.swift

import CryptoSwift
import CommonCrypto

#if canImport(CryptoKit)
import CryptoKit
#endif

public final class PublicKeyPinner {
  ...
  /// Creates a hash from the received data using the `sha256` algorithm.
  /// `Returns` the `base64` encoded representation of the hash.
  ///
  /// To replicate the output of the `openssl dgst -sha256` command, an array of specific bytes need to be appended to
  /// the beginning of the data to be hashed.
  /// - Parameter data: The data to be hashed.
  private func hash(data: Data) -> String {
      // Add the missing ASN1 header for public keys to re-create the subject public key info
      var keyWithHeader = Data(rsa2048Asn1Header)
      keyWithHeader.append(data)
      // Check if iOS 13 is available, and use CryptoKit's hasher
      if #available(iOS 13, *) {
          return Data(SHA256.hash(data: keyWithHeader)).base64EncodedString()
      } else {
          ...
      }
  }
}