密码术是对信息进行编码实现隐藏信息的一门学问。例如你想把信用卡号码告诉商家来买东西,但不希望任何有恶意的第三方截取你的信用卡号码,采用密码方法可以隐藏和保护需要保密的消息,使未受权者不能提取信息。被隐藏消息称做明文,密码可将明文变换成另一种隐藏的形式,称为密文 Cryptography is a science that encodes information to hide it. For example, you want to tell the merchant to buy a credit card number, but do not want any malicious third party to intercept your credit card number. The password method can hide and protect the information that needs to be kept secret so that the unauthorized person can not extract the information. Hidden messages are called plaintexts, and passwords can transform plaintext into another hidden form, called a ciphertext