SSL对性能有一定影响，因为每个发送到服务器和从服务器传出的数据片都必须加密。
SSL can have some performance impacts because every piece of data sent to and from the server must be decrypted.
当然，从浏览器到服务器发送的数据并未压缩，因而没有携带这种额外的加密。
Of course, data being sent from the browser to the server is not compressed and therefore doesn't carry this extra encryption.
密钥—密钥就一些密码数据，通常使用特定加密算法从用户的密码中获得。
Key - a key is cryptographic data which is usually derived from a user's password using specific encryption algorithms.
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