Playfair密码算法Java实现

 密码课程设计第一个小题目，Playfair密码算法实现。JAVA版实现。

 

import java.util.*;

public class PlayfairCoder{

    public static int checkChar(char c){

        if(c>='A'&&c<='Y')

            return 1;

        else

            return 0;

    }

    /*

     *格式化密钥材料

     */

    public static String formatKey(String key){

        StringBuffer sb=new StringBuffer();

        HashSet<Character> hs=new HashSet<Character>();

        char n;

        String k=key.toUpperCase();

        char[] detail=new char[25];

                for(int i=0,j=65;i<25;i++,j++)

                        detail[i]=(char)j;

        for(int i=0;i<k.length();i++){

            n=k.charAt(i);

            if(!hs.contains(n)&&checkChar(n)==1){

                sb.append(n);

                hs.add(n);

            }

        }

        int i=0;

        while(sb.length()!=25){

            char t=detail[i];

            if(!hs.contains(t)){

                sb.append(t);

                hs.add(t);

            }

            i++;

        }

        return sb.toString();

    }

    /*

     *生成密钥矩阵

     */

    public static char[][] initKey(String k){

        char[][] key=new char[5][5];

        String s=formatKey(k);

        int m=0;

        for(int i=0;i<5;i++)

            for(int j=0;j<5;j++){

                key[i][j]=s.charAt(m);

                m++;

        }

        return key;

    }

    /*

         *格式化明文

         */

    public static String formatData(String data,String sign){

        String updata=data.toUpperCase();

        String ming="",temp="";

        char c;

        Stack<Character> stack=new Stack<Character>();

        for(int i=0;i<updata.length();i++){

            c=updata.charAt(i);

            if(checkChar(c)==1){

                if(stack.size()%2!=0){

                    if(stack.peek()==c){

                        stack.push(sign.charAt(0));

                        stack.push(c);

                    }

                    else

                        stack.push(c);

                }

                else

                    stack.push(c);

            }

        }

        while(stack.size()>0)

            temp+=stack.pop();

        for(int i=temp.length()-1;i>-1;i--)

            ming+=temp.charAt(i);

        if(ming.length()%2!=0)

            ming+=sign.charAt(0);

        return ming;

    }

    public static String getEnData(char a,char b,char[][] k){

        String result="";

        int h=0,l=0,m=0,n=0;

        for(int i=0;i<k.length;i++)

            for(int j=0;j<k[i].length;j++){

                if(a==k[i][j]){

                    h=i;

                    l=j;

                }

                if(b==k[i][j]){

                    m=i;

                    n=j;

                }

        }

        if(h!=m&&l!=n)

            result=result+k[h][n]+k[m][l];

        else if(h==m){

            if(l==4)

                result=result+k[h][0]+k[h][n+1];

            else if(n==4)

                result=result+k[h][l+1]+k[h][0];

            else

                result=result+k[h][l+1]+k[h][n+1];

        }

        else if(l==n){

            if(h==4)

                                result=result+k[0][l]+k[m+1][l];

                        else if(m==4)

                                result=result+k[h+1][l]+k[0][l];

                        else

                                result=result+k[h+1][l]+k[m+1][l];

                }

        return result;

    }

    public static String getDeData(char a,char b,char[][] k){

        String result="";

                int h=0,l=0,m=0,n=0;

                for(int i=0;i<k.length;i++)

                        for(int j=0;j<k[i].length;j++){

                                if(a==k[i][j]){

                                        h=i;

                                        l=j;

                                }

                                if(b==k[i][j]){

                                        m=i;

                                        n=j;

                                }

                }

                if(h!=m&&l!=n)

                        result=result+k[h][n]+k[m][l];

                else if(h==m){

                        if(l==0)

                                result=result+k[h][4]+k[h][n-1];

                        else if(n==0)

                                result=result+k[h][l-1]+k[h][4];

                        else

                                result=result+k[h][l-1]+k[h][n-1];

                }

                else if(l==n){

                        if(h==0)

                                result=result+k[4][l]+k[m-1][l];

                        else if(m==0)

                                result=result+k[h-1][l]+k[4][l];

                        else

                                result=result+k[h-1][l]+k[m-1][l];

                }

                return result;

    }

    /*

     *加密

     */

    public static String encrypt(String key,String data,String sign){

        char[][] k=initKey(key);

        String d=formatData(data,sign);

        String endata="";

        int i=0,j=1;

        char a,b;

        while(j<d.length()){

            a=d.charAt(i);

            b=d.charAt(j);

            endata=endata+getEnData(a,b,k);

            i+=2;

            j+=2;

        }

        return endata;

    }

    /*

     *解密

     */

    public static String decrypt(String key,String data,String sign){

        char[][] k=initKey(key);

        String dedata="";

        int i=0,j=1;

        char a,b;

        while(j<data.length()){

            a=data.charAt(i);

            b=data.charAt(j);

            dedata=dedata+getDeData(a,b,k);

            i+=2;

            j+=2;

        }

        dedata=dedata.replaceAll(sign,"");

        return dedata;

    }

    public static void main(String[] str){

        Scanner sc=new Scanner(System.in);

        System.out.print("请输入密钥: ");

        String arr=sc.nextLine();

        System.out.print("请输入明文: ");

        String m=sc.nextLine();

        System.out.print("请输入标志字符");

        String sign=sc.nextLine().toUpperCase();

        String t=formatData(m,sign);

        System.out.println("明文格式化: "+t+"\n密钥矩阵:");

        char[][] testarr=initKey(arr);

        for(int i=0;i<5;i++)

            for(int j=0;j<5;j++){

                System.out.print(testarr[i][j]+"   ");

                if(j==4)

                System.out.println("");

        }

        String jia=encrypt(arr,m,sign);

        System.out.println("加密后: "+jia);

        System.out.println("解密后: "+decrypt(arr,jia,sign));



    }

}