Secret key distribution的用法和樣例：
例句
- Users can make their public keys freely available or place them at a key distribution centre for others to access.
用戶可以讓公開密鑰自由使用或者把公開密鑰放在可由別人存取的密鑰分配中心。 - The private key can guarantee the security of communication, while the distribution is still a problem.
私鑰系統雖然安全，但是密鑰分配的安全性在經典系統中一直難以得到保證。
