Cryptography: Caesar Cipher Encryption / Decryption in Swift

CaesarCipher.swift

let originalString = "Hello"
let encodedPlacement = 4
var cipheredString = ""
var decipheredString = ""

  func CaesarCipherEncrypt(_ str: String, _ num: Int) -> String {

    var result = "";
    for ch in str {
      if let asciiValue = ch.asciiValue {
        if asciiValue > 64 && asciiValue < 91 {
          let a = Int(asciiValue) + num - 65
          let total = UInt8(((a) % 26) + 65)
          let string =  UnicodeScalar(total)

          result += String(string)
        }else {
          let a = Int(asciiValue) + num - 97
          let total = UInt8(((a) % 26) + 97)
          let string =  UnicodeScalar(total)

          result += String(string)
        }
      }
    }
  return result;
}

func CaesarCipherDecrypt(_ str: String, _ num: Int) -> String {
  var result = "";
  for ch in str {
    if let asciiValue = ch.asciiValue {

      if asciiValue > 64 && asciiValue < 91 {
        let a = Int(asciiValue) - num - 65
        let total = UInt8(((a) % 26) + 65)
        let string =  UnicodeScalar(total)

        result += String(string)
      }else {
        let a = Int(asciiValue) - num - 97
        let total = UInt8(((a) % 26) + 97)
        let string =  UnicodeScalar(total)

        result += String(string)
      }
    }
  }
  return result;
}

cipheredString = CaesarCipherEncrypt(originalString, encodedPlacement)
decipheredString = CaesarCipherDecrypt(cipheredString, encodedPlacement)