密钥：密钥是一种在明文与密文之间相互转换的方式。
Key: Key is a means of converting a plain-text into cipher-text and vice versa.
以明文方式传输消息、传输加密的但以明文方式存储的消息、或者由于密钥被窃取或通过密码分析获取后对消息进行解密，在以上几种情况下都可能发生这种攻击。
This can happen to messages being transmitted in the clear, transmitted encrypted but stored in the clear, or decryption of messages due to stolen key or cryptoanalysis.
如果有完整的明文和对应的密文可是实现破译功能，即得出加密密钥。
If there is an express integrity and the corresponding ciphertext But achieving deciphering function, which is derived encryption keys.
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