Is the regularity shown in this encoded message noise or structure?
Can you crack these very difficult challenge ciphers? How might you systematise the cracking of unknown ciphers?
In 'Secret Transmissions', Agent X could send four-digit codes error free. Can you devise an error-correcting system for codes with more than four digits?
This challenge cipher forms part of a very difficult sequence of ciphers suitable for keen groups or individuals, maths clubs and very optional homework challenges. Don't try this in the classroom!