How, from bizarre ancient markings to random numbers and letters, codes and ciphers have been used for millennia to send secret messages, hide identities.How, from bizarre ancient markings to random numbers and letters, codes and ciphers have been used for millennia to send secret messages, hide identities.How, from bizarre ancient markings to random numbers and letters, codes and ciphers have been used for millennia to send secret messages, hide identities.