Imagine having to crack open a codebook to connect to youtube!
想象一下必须破解密码本才能连接到 youtube!
科技 Crash Course
In the old days, keys would be shared by voice, or physically; for example, the Germans distributed codebooks with daily settings for their Enigma machines.
A codebook is a type of document used for gathering and storing codes. Originally codebooks were often literally books, but today codebook is a byword for the complete record of a series of codes, regardless of physical format.