> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/c/caesar_cipher.md).

# Caesar cipher

```ruby
func caesar(msg, key, decode=false) {
    decode && (key = (26 - key))
    msg.gsub(/([A-Z])/i, {|c| ((c.uc.ord - 65 + key) % 26) + 65 -> chr})
}
 
var msg = 'THE FIVE BOXING WIZARDS JUMP QUICKLY'
 
var enc = caesar(msg, 10)
var dec = caesar(enc, 10, true)
 
say "msg: #{msg}"
say "enc: #{enc}"
say "dec: #{dec}"
```

#### Output:

```
msg: THE FIVE BOXING WIZARDS JUMP QUICKLY
enc: DRO PSFO LYHSXQ GSJKBNC TEWZ AESMUVI
dec: THE FIVE BOXING WIZARDS JUMP QUICKLY
```