X78JPtux

1// Form1.cs
2
3using System;
4using System.Collections.Generic;
5using System.ComponentModel;
6using System.Data;
7using System.Drawing;
8using System.Linq;
9using System.Text;
10using System.Threading.Tasks;
11using System.Windows.Forms;
12using System.Security.Cryptography;
13using System.IO;
14
15namespace ei_si_worksheet4
16{
17    public partial class Form1 : Form
18    {
19        // Constants
20        const string FILENAME_PUBLIC_KEY = "PublicKey.xml";
21        const string FILENAME_PRIVATE_PUBLIC_KEY = "PrivatePublicKey.xml";
22
23        public Form1()
24        {
25            InitializeComponent();
26        }
27
28        private void Form1_Load(object sender, EventArgs e)
29        {
30
31        }
32
33        private void ButtonGererateKeys_Click(object sender, EventArgs e)
34        {
35            try
36            {
37                using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
38                {
39                    // FALSE -> EXPORTS ONLY THE PUBLIC KEY
40                    textboxPublicKey.Text = rsa.ToXmlString(false);
41
42                    //TRUE -> EXPORTS THE PUBLIC AND PRIVATE KEY
43                    textboxBothKeys.Text = rsa.ToXmlString(true);
44                }
45            }
46            catch (ArgumentNullException ex)
47            {
48                MessageBox.Show($"Error: {ex.Message}");
49            }
50        }
51
52        private void ButtonSavePublicKey_Click(object sender, EventArgs e)
53        {
54            File.WriteAllText(FILENAME_PUBLIC_KEY, textboxPublicKey.Text);
55            MessageBox.Show("File created with Public Key!");
56        }
57
58        private void ButtonSaveKeys_Click(object sender, EventArgs e)
59        {
60            File.WriteAllText(FILENAME_PRIVATE_PUBLIC_KEY, textboxBothKeys.Text);
61            MessageBox.Show("File created with Public Key and Private key!");
62        }
63
64        private void ButtonEncrypt_Click(object sender, EventArgs e)
65        {
66            string publicKey = null;
67            byte[] secretKey = null; // Plain texto to be ciphered
68            byte[] cipheredData = null;
69 
70            try
71            {
72                secretKey = Encoding.UTF8.GetBytes(textboxSymmentricKey.Text);
73
74                using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
75                {
76                    // Get public key from the "person to whom we are going to send the secret key"
77                    publicKey = File.ReadAllText(FILENAME_PUBLIC_KEY);
78                    rsa.FromXmlString(publicKey);
79
80                    // Encrypt data using the public key
81                    cipheredData = rsa.Encrypt(secretKey, true);  // True -> OAEP padding
82                    textboxSymmetricKeyEncrtypted.Text = Convert.ToBase64String(cipheredData);
83                    textboxBitSize.Text = (cipheredData.Length * 8).ToString();
84                }
85            }
86            catch (CryptographicException ex)
87            {
88                MessageBox.Show($"Error encrypting the key. Details: {ex.Message}");
89            }
90        }
91
92        private void ButtonDecrypt_Click(object sender, EventArgs e)
93        {
94            string privateKey = null;
95            byte[] cipheredData = null;
96            byte[] secretKey = null;    // plain text
97
98            try
99            {
100                cipheredData = Convert.FromBase64String(textboxSymmetricKeyEncrtypted.Text);
101
102                using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
103                {
104                    privateKey = File.ReadAllText(FILENAME_PRIVATE_PUBLIC_KEY);
105                    rsa.FromXmlString(privateKey);
106
107                    secretKey = rsa.Decrypt(cipheredData, true);    // True -> OAEP padding
108
109                    textboxSymmetricKeyDecrypted.Text = Encoding.UTF8.GetString(secretKey);
110                }
111            }
112            catch (CryptographicException ex)
113            {
114                MessageBox.Show($"Error decrypting the secret key. Details: {ex.Message}");
115            }
116        }
117    }
118}