雙語暢銷書《艾倫圖靈傳》第5章:解謎接力賽(10)
So printed with the table there was another list of eight-letter sequences such as 'BMTVKZMD'.
The clerk would choose one of these sequences and add it to the beginning of the message proper.
操作員會選擇其中一個序列，把它添加到密文的開頭。The receiver, equipped with the same list, could then see which table was being used.
接收者擁有同樣的列表，於是就知道該查找哪一張替換表。
This simple rule illustrated a very general idea.
這個簡單的方法，體現了一個非常重要的概念。In practical cryptography, as opposed to the setting of isolated puzzles, there would usually be some part of the message transmitted which did not convey the text itself, but which conveyed instructions on how to decipher it.
在密碼技術中，密碼的某些部分並不傳遞消息，而且說明如何解碼。Such elements of the transmission, which would be disguised and buried within it, were called indicators.
這種僞裝起來、隱藏在密文中的信號，稱爲指示信號。Even a one-time pad system might employ indicators, to give a check on which page of the pad was being used.
一次性密鑰系統，也是通過這種指示信號，來說明使用的是哪一頁密鑰。In fact, unless everything were spelt out in advance and in complete, rigid, detail, without any chance of ambiguity or error, there would have to be some form of indicator.
除非雙方事先把所有的一切都固定下來，進行詳細的約定，而且不會發生任何變化，否則都必須要在密文中加入某種形式的指示信號。It must surely have struck Alan, who had been thinking at least since 1936 about 'the most general kind of code or cipher', that this mixing of instructions and data within a transmission was reminiscent of his 'universal machine',
從1936年開始，艾倫就在思考一種通用的密碼系統，現在他非常興奮，因爲這種數據與指令相結合的模式，使他立即聯想到他的通用機。which would first decipher the 'description number' into an instruction, and then apply that instruction to the contents of its tape.
他的機器首先把描述數解碼成指令，然後根據指令來操作紙帶上的數據。Indeed any cipher system might be regarded as a complicated 'mechanical process' or Turing machine, involving not just the rules for adding or substituting, but rules for how to find, apply and communicate the method of encipherment itself.
實際上，任何密碼系統，都可以看成是一個機械的過程，也就是圖靈機，不光是加法或替換，還包括對本身的操作過程進行查找和執行。Good cryptography lay in the creation of an entire body of rules, not in this or that message.
良好的密碼學是建立在整個規則基礎上的，而不是在這個或那個信息中。
