A cypher on the other hand requires no 'code-book' as such because it relies on a manipulation of the letters of a message in such a way as to render them nonsensical to anyone other than the intended recipient, who simply performs the same manipulation, but in reverse in order to reveal the messages meaning. Examples of such manipulations might be reversing the alphabet to make z equate to a, y to b, x to c.... and so on, or we might shift the letters of the alphabet by any number of letters to the right or left - say make a be c, b be d and c be e ....etc. Much more complex manipulations can be devised, particularly using computers, that make such ciphers almost impossible to crack, but apparently all languages have tell-tale clues that enable code-breakers to get a finger hold through the door toward doing so. In english for example a single letter in an encrypted cypher would almost have to be 'a'. Certain letters nearly always occur together [q followed by u for eg] and letter frequency analysis that once known, allow for tentative identification of letters within the cypher. Gradually using such small advances a cypher can be broken down [sometimes] and its message revealed. The enigma code was broken when the Bletchley team realised that words like 'the weather report' and 'heil hitler' could be guarrenteed to be in certain messages and this was the hairline fault they prised their fingers into in order to break it.
Another way of encryption might be by hiding the real message within a framework of nonsense letters such that only a person who knows which letters to read could reveal the message. It could be as simple as 'every fouth letter, or I might for example agree with V. that 'pi' would be the key [?]. In this case when recieving a message he would read the third letter[3], the fourth [1], the eigth [4], the ninth [1].....etc. I'm not sure how this kind of encryption [is this a code or a cypher?] could be broken without knowledge of the 'key'.
The methods of deciphering encrypted messages can equally be used in the elucidation and translation of acient and forgotten scripts. Champillion was able to crack the meaning of ancient egyptian heiroglyphs by virtue of the use of cartouches to encircle the pharoes name on the Rosetta stone. The three scripts of the stone [heiroglyph, greek and demotic I think] two of which were understood, enabled him to elucidate the third [I expect I've oversimplified this but I believe it was something like that].
What a fascinating subject. If anyone has any observations about where I might be adrift or indeed any further information to add I'd be gratefull to hear it. Perhaps we could even try a few out for fun.
