實際上，適當的密碼學機制（包含加解密法）應該保持安全，即使敵人知道了使用何種演算法。對好的加密法來說，金鑰的秘密性理應足以保障資料的機密性。
（Wikipedia：密碼學／密碼學與密碼分析的歷史／現代密碼學）
從保護演算法（加密的方法）變成發展即使公開敵人也無法破解密文的演算法，密碼學就此正式從古典密碼學踏入現代密碼學的年代。
現代密碼學是怎麼一回事呢？留待下回分曉吧！
In fact, appropriate cryptography mechanism
(including encryption and decryption) should keep the cipher text safe even if
the enemy knows what algorithm which it using.
For a good encryption, the secret of the key should be sufficient
to protect the confidentiality of the data.
(Wikipedia: cryptography / cryptography and the history of crypt analysis / modern cryptography)
From the protection algorithm (encryption method)
to the new developing algorithm which makes the enemy can not decode of the cipher text, even the new algorithm is open to the public,
cryptography formally entered the dynasty of modern cryptography from the classical cryptography dynasty.
What is the modern cryptography? Let's left it for the next!
