20120709-the key factor affecting explicit or implicit interface implementation

本文详细探讨了在面向对象编程中,如何通过实现接口来扩展类的功能,包括接口的隐式实现、显式实现以及一个类同时实现多个接口的情况。通过实例展示了不同情况下的接口使用与类的行为差异。



1. first situation:

    one class implement one interface

   and all the interface implementation is implicit

   

 public interface IBankAccount
  {
    void PayIn(decimal amount);
    bool Withdraw(decimal amount);

    decimal Balance{get;}

  }


 

public class SaverAccount : IBankAccount
  {
    //类SaverAccount独有的
    public void PayIn2()
    {

    }

    //接口IBankAccount可以访问的
    public void PayIn(decimal amount)
    {

    }
    //接口IBankAccount可以访问的
    public bool Withdraw(decimal amount)
    {
      return false;
    }
    //接口IBankAccount可以访问的
    public decimal Balance
    {
      get
      {
        return 1;
      }
    }
  }


when use IBankAccount

  IBankAccount ba = new SaverAccount();
      ba.PayIn(1);
      SaverAccount sa = new SaverAccount();
      sa.PayIn(2);
      sa.PayIn2();//接口不能调用


 

2. the second situation

 

 

//the tiny difference is PayIn is explicit implementation
   //接口IBankAccount可以访问的
    public void IBankAccount.PayIn(decimal amount)
    {

    }

 

 //此时PayIn不可调用
      sa.PayIn(2);

3. one class implement multiple interface

each interface can only invoke the member and function that is assigned by itself.

if the class explicit one interface's function, the instance of this class couldn't invoke the explicit interface fuction

 

 

 

 

 

 

 

    
8.3 MAC Algorithms used for Extraction and Expansion Provided that the targeted security strength can be supported (see Tables 4 and 5 in Section 5.2), this Recommendation permits either HMAC-hash (i.e., HMAC implemented with an appropriately chosen approved hash function, hash) or AES-CMAC (i.e., the CMAC mode of AES-128, AES192, or AES-256) to be selected as the MAC algorithm used in the randomness-extraction step of the key-derivation procedure specified in Section 5.1. The PRF-based KDF used in the key-expansion step of the procedure also requires an appropriate MAC (to serve as the PRF). While it may be technically feasible (in some cases) to employ completely different MAC algorithms in the two steps of the specified key-derivation procedure, this Recommendation does not permit such flexibility. Instead, the following restrictions have been placed on MAC selection (see Sections 5 and 7): • When HMAC-hash is chosen for use in the randomness-extraction step, the same MAC algorithm (i.e., HMAC-hash with the same approved hash function, hash) shall be employed to implement the PRF-based KDF used in the key-expansion step. • When AES-128-CMAC, AES-192-CMAC, or AES-256-CMAC is chosen for use in the randomness-extraction step, the MAC algorithm employed by the PRF-based KDF used in the key-expansion step shall be AES-128-CMAC, the CMAC mode of AES-128. (AES-128 is the only AES variant that can employ the 128-bit KDK produced by AES-N-CMAC during the randomness-extraction step.) • The MAC algorithm selected for the implementation of a two-step key-derivation method shall be capable of supporting the targeted security strength as determined by consulting Tables 4 and 5 in Section 5.2. (This limits the use of AES-CMAC to cases where the targeted security strength is no more than 128 bits.) The imposed restrictions are intended to reduce the overall complexity of the resulting implementations, promote interoperability, and simplify the negotiation of the parameters and auxiliary functions affecting the security strength supported by the key-derivation procedure. Note: At this time, KMAC has not been specified for use in the implementation of a two-step keyderivation procedure. This restriction may be reconsidered once a KMAC-based KDF has been approved for use as a PRF-based KDF in a revision of [SP 800-108] 这段说了什么
07-10
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