Decoding an x.509 public key?

Hi,

I have a base64-encoded string which I am told contains an x.509 public key. I need to extract the key and use it to encode a message.

Decoding from the string to a Data object yields 294 bytes of data.

I am not sure what to do next. I tried using SecKeyCreateWithData, which provided a result, but when I attempted to encrypt my message I got an error (OSStatus -50).

Here is my code:

  let keyDict:[NSObject:NSObject] = [
       kSecAttrKeyType: kSecAttrKeyTypeRSA,
       kSecAttrKeyClass: kSecAttrKeyClassPublic,
       kSecAttrKeySizeInBits: NSNumber(value: 2048),
       kSecReturnPersistentRef: true as NSObject
  ]

  let publickeysi = SecKeyCreateWithData(data2! as CFData, keyDict as CFDictionary, nil)

  //Encrypt a string with the public key
  let message = clearStr
  let blockSize = SecKeyGetBlockSize(publickeysi!)
  var messageEncrypted = [UInt8](repeating: 0, count: blockSize)
  var messageEncryptedSize = blockSize

  var status: OSStatus!

  status = SecKeyEncrypt(publickeysi!, SecPadding.PKCS1, message, message.count, &messageEncrypted, &messageEncryptedSize)

  if status != noErr {
       print("Encryption Error!")
  }