Cryptography-Code-Bunch/Playfair-Cipher-Decryption.java at master · astrodestroyergithub/Cryptography-Code-Bunch · GitHub

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import java.util.Scanner;

public class MyProgram{

	static void decrypt(String encpt, String key) {

		char[] encpt_arr=encpt.toCharArray();
		char[] key_arr=key.toCharArray();

		char[] alpha={'A','B','C','D','E','F','G','H','I','K','L',
		'M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

		char[][] table=new char[5][5];

		int ctr=-1;
		for(int i=0;i<key_arr.length;i++)
			for(int j=0;j<25;j++)
				if(key_arr[i]==alpha[j])
				{
					ctr++;
					int round = ctr/5;
					table[round][ctr%5]=alpha[j];
					alpha[j]='0';
					break;
				}
		for(int i=0;i<alpha.length;i++)
		{
				if(alpha[i]!='0')
				{
					ctr++;
					int round = ctr/5;
					table[round][ctr%5]=alpha[i];
				}
		}

		System.out.println("\nThe Reference Table is:");
		for(int i=0;i<5;i++)
		{
			for(int j=0;j<5;j++)
				System.out.print(table[i][j]+" ");
			System.out.println();
		}

		char[] any=new char[encpt_arr.length];
		int any_ctr=0;

		for(int i=0;i<encpt_arr.length;i=i+2)
		{
			int row1=0,row2=0,col1=0,col2=0;
			for(int j=0;j<5;j++)
			{
				for(int k=0;k<5;k++)
				{
					if(encpt_arr[i]==table[j][k])
					{
						row1=j;
						col1=k;
						break;
					}
				}
			}
			for(int j=0;j<5;j++)
			{
				for(int k=0;k<5;k++)
				{
					if(encpt_arr[i+1]==table[j][k])
					{
						row2=j;
						col2=k;
						break;
					}
				}
			}
			if(row1==row2)
			{
				col1=(col1-1+5)%5;
				col2=(col2-1+5)%5;
				any[any_ctr++]=table[row1][col1];
				any[any_ctr++]=table[row2][col2];
			}
			else if(col1==col2)
			{
				row1=(row1-1+5)%5;
				row2=(row2-1+5)%5;
				any[any_ctr++]=table[row1][col1];
				any[any_ctr++]=table[row2][col2];
			}
			else if(row1!=row2 && col1!=col2)
			{
				int row=0,col=0;
				row=row1;
				col=col2;
				any[any_ctr++]=table[row][col];
				row=row2;
				col=col1;
				any[any_ctr++]=table[row][col];
			}
			else
			{
			}
		}

		System.out.print("\nThe Intermediate Text is: ");
		for(int i=0;i<any_ctr;i++)
			System.out.print(any[i]);

		char[] decpt_arr=new char[100];
		int decpt_arr_ctr=0;

		for(int i=0;i<any_ctr;i++)
		{
			if(i==0)
			{
				decpt_arr[decpt_arr_ctr++]=any[i];
				continue;
			}
			if(i==1 && any[i-1]==any[i+1] && any[i]=='X')
			{
				continue;
			}
			if(i==1 && any[i-1]!=any[i+1] && any[i]!='X')
			{
				decpt_arr[decpt_arr_ctr++]=any[i];
				continue;
			}
			if(i==2 && any[i-1]==any[i+1] && any[i]=='X')
			{
				continue;
			}
			if(i==2 && any[i-1]!=any[i+1] && any[i]!='X')
			{
				decpt_arr[decpt_arr_ctr++]=any[i];
				continue;
			}
			if(i!=any_ctr-2 && i!=any_ctr-1
			&& any[i-1]==any[i+1] && any[i]=='X')
			{
				continue;
			}
			if(i!=any_ctr-2 && i!=any_ctr-1
			&& any[i-1]==any[i+1] && any[i]!='X')
			{
				decpt_arr[decpt_arr_ctr++]=any[i];
				continue;
			}
			if(i==any_ctr-2 && any[i-1]==any[i+1] && any[i]=='X')
			{
				continue;
			}
			if(i==any_ctr-2 && any[i-1]==any[i+1] && any[i]!='X')
			{
				decpt_arr[decpt_arr_ctr++]=any[i];
				continue;
			}
			if(i==any_ctr-1 && i%2!=0 && any[i]=='X')
			{
				continue;
			}
			if(i==any_ctr-1 && any[i]!='X')
			{
				decpt_arr[decpt_arr_ctr++]=any[i];
				continue;
			}
			if(i==any_ctr-1 && i%2==0 && any[i]=='X')
			{
				continue;
			}
			if(i>=0)
			{
				decpt_arr[decpt_arr_ctr++]=any[i];
				continue;
			}
		}

		System.out.print("\n\nThe Decrypted Text is: ");
		for(int i=0;i<decpt_arr_ctr;i++)
			System.out.print(decpt_arr[i]);

	}

	public static void main(String[] args) {

		String encpt;
		System.out.print("Enter Ciphertext: ");
		Scanner scanner = new Scanner(System.in);
		encpt = scanner.nextLine();
		String key;
		System.out.print("Enter Key: ");
		key = scanner.nextLine();

		decrypt(encpt,key);
	}
}