Ceaser-Cipher-algorithm/Encryption_Decryption.java at main · NikhilTeja21/Ceaser-Cipher-algorithm · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
//Encrytion of text
import java.util.Scanner;
public class Encryption_Decryption    //File name
{

    public static String Encrytion(String message,String low,String up,String lower,String upper)
    {
        StringBuilder Encrypt = new StringBuilder(message);
        for(int chr=0;chr<Encrypt.length();chr++)
        {
            char pointer = Encrypt.charAt(chr);
            //If the character is upper case
            if(Character.isUpperCase(pointer))
            {
                int index = up.indexOf(pointer);
                if(index!=-1)
                {
                    char new_pointer = upper.charAt(index);
                    Encrypt.setCharAt(chr,new_pointer);
                }
            }
            //If the character is lower case
            else if(Character.isLowerCase(pointer))
            {
                int index = low.indexOf(pointer);
                if(index!=-1)
                {
                    char new_pointer = lower.charAt(index);
                    Encrypt.setCharAt(chr,new_pointer);
                }
            }
        }
        return Encrypt.toString();
    }


    public static void Decryption(String message,String low,String up,String lower,String upper)
    {
        System.out.println("\n\nMessage before Decryption : "+Encrytion(message, low, up, lower, upper));
        StringBuilder Decrypt = new StringBuilder(message);
        for(int chr=0;chr<Decrypt.length();chr++)
        {
            char pointer = Decrypt.charAt(chr);
            //If the character is upper case
            if(Character.isUpperCase(pointer))
            {
                int index = upper.indexOf(pointer);
                if(index!=-1)
                {
                    char new_pointer = up.charAt(index);
                    Decrypt.setCharAt(chr,new_pointer);
                }
            }
            //If the character is lower case
            else if(Character.isLowerCase(pointer))
            {
                int index = lower.indexOf(pointer);
                if(index!=-1)
                {
                    char new_pointer = low.charAt(index);
                    Decrypt.setCharAt(chr,new_pointer);
                }
            }
        }
        System.out.println("Message after decryption : "+Decrypt);
    }

    public static void Conversion(String input,String lower,String upper,int private_key)
    {
        Scanner ipt = new Scanner(System.in);
        String upper_converted_text = upper.substring(private_key)+upper.substring(0,private_key);
        //Shifting the lower case alphabets using private key

        String lower_converted_text = lower.substring(private_key)+lower.substring(0,private_key);
        //Shifting the upper case alphabest using private key

        System.out.println("Message after encryption : "+Encrytion(input,lower,upper,lower_converted_text,upper_converted_text));

        System.out.print("\n\nDo you want to decrypt the data ?? Press 1 : ");
        int press = ipt.nextInt();
        if(press==1)
        {
            System.out.print("Enter the private key : ");
            int key = ipt.nextInt();

            if(key>26)
            {
                key = key%26;
            }
            if(key==26)
            {
                key = 21;
            }

            if(key==private_key)
            Decryption(Encrytion(input,lower,upper,lower_converted_text,upper_converted_text),lower,upper,lower_converted_text,upper_converted_text);
            else
            {
                System.out.println("Sorry, Wrong key entered. Please start from the beggining");
            }
        }


        System.out.println("\n\n\t\t======Thank you======\n\n");

    }


    public static void main(String... args)
    {
        System.out.println("\n\n\t\tCeaser Cipher Algorithm\n");
        Scanner ipt = new Scanner(System.in);
        System.out.print("\nEnter a private message : ");
        String input = ipt.nextLine();

        String lower_alpha = "abcdefghijklmnopqrstuvwxyz";    //If the character is lower converts into lower cipher text
        String upper_alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";    //If the character is upper converts into upper cipher text

        System.out.print("Enter a private key : ");
        int private_key = ipt.nextInt();

        if(private_key>26)
        {
            private_key = private_key%26;
        }
        if(private_key==26)
        {
            private_key = 21;
        }

        System.out.println("\n\nMessage before encryption : "+input);

        Conversion(input,lower_alpha,upper_alpha,private_key);

    }
}