The location of the ship is a closely guarded secret.

那艘船的方位是高度机密。

《牛津词典》

This was possible because of the Navy's formerly top-secret system of underwater listening devices spanning the oceans.

这是可能的，因为海军曾使用的水下监听设备的最高机密系统覆盖多个大洋。

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It is also possible to use the documents to make deductions about the coalition forces' list of enemies, which is still top secret.

这些文件还可以用来从依然是最高机密的敌方联军名单列表中做减法，减去那些已被猎杀的人。

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But in this movie, the kid gets a little secret decoder ring.

不过在这个电影中，那个小孩得到了一个小的机密解码戒指。

哈佛公开课 - 计算机科学课程节选

It's a secret number so that if Julius Caesar scrambled his message with the key 13, well, then the recipient had better know what that number is or realistically, -- and this is why it's kind of hard to buy -- into some of these age old algorithms, -- what would an alternative approach be to figuring out Julius Caesar's messages to his generals if he didn't know that secret number was 13?

它是一个机密的数字，以至于,如果凯撒大帝使用密钥13加密了它的消息，然后接收者最好知道那个数字是什么,实际上--这就是为什么很难,破解这些古老的算法-,有什么变换方法使凯撒大帝的将军,可以解密凯撒大帝的消息，如果他不知道,那个机密数字是13呢？

哈佛公开课 - 计算机科学课程节选