public byte[] Create(byte[] text, RSA RSA)
{
SHA_1 SHA1 = new SHA_1();
byte[] SHAHash = new byte[20];
SHAHash = SHA1.GetHash(text).Value;
BigInteger BI_Hash = new BigInteger(SHAHash);
byte[] signature = RSA.EncryptHash(BI_Hash).ToByteArray();
return(signature);
}
private void btnVerify_Click(object sender, RoutedEventArgs e)
{
if ((FileName == null) || (FileName == ""))
{
MessageBox.Show("Error: Choose file.");
}
else if ((Signature == null) || (Signature == ""))
{
MessageBox.Show("Error: Choose file with signature.");
}
else
{
BigInteger eps, r; // public key
if (IsPublicKeyValid(out eps, out r))
{
RSA RSA = new RSA(eps, r);
SHA_1 SHA1 = new SHA_1();
byte[] realHash = new byte[20];
realHash = SHA1.GetHash(Message).Value;
// BigInteger values are represented in little endian
Array.Reverse(realHash);
// sure that a positive value is not incorrectly instantiated as a negative value
// by adding a byte whose value is zero to the end of the array
byte[] temp = new byte[realHash.Length];
Array.Copy(realHash, temp, realHash.Length);
realHash = new byte[temp.Length + 1];
Array.Copy(temp, realHash, temp.Length);
// decimal representation of hash
tbHashDecimal.Text = new BigInteger(realHash).ToString();
//hexadecimal representation of hash
string hexHash = new BigInteger(realHash).ToString("X");
if (hexHash[0] == '0')
{
hexHash = hexHash.Substring(1);
}
tbHashHex.Text = hexHash;
// convert signature to BigInteger
BigInteger BI_Hash = BigInteger.Parse(Signature);
//encrypt hash from file using public key
byte[] checkedHash = new byte[20];
RSA Rsa = new RSA(eps, r);
checkedHash = Rsa.DecryptHash(BI_Hash).ToByteArray();
if (new BigInteger(realHash) > RSA.R)
{
MessageBox.Show("Error: Hash is greater than R.");
return;
}
// output encrypted hash from file
tbCheckedHash.Text = new BigInteger(checkedHash).ToString();
if (new BigInteger(checkedHash) == new BigInteger(realHash))
{
MessageBox.Show("Digital signature is correct. File is authentic.");
}
else
{
MessageBox.Show("Digital signature isn't correct!");
}
}
}
}
private void btnSign_Click(object sender, RoutedEventArgs e)
{
if ((FileName == null) || (FileName == ""))
{
MessageBox.Show("Error: choose file");
}
else if ((Message == null) || (Message.Length == 0))
{
MessageBox.Show("Error: empty file");
return;
}
else
{
BigInteger p, q, eps, d; // secret key
if (IsSecretKeyValid(out p, out q, out eps, out d))
{
// modulo
BigInteger r;
r = p * q;
tbR.Text = r.ToString();
RSA RSA = new RSA(p, q, eps, d, r);
SHA_1 SHA1 = new SHA_1();
byte[] SHAHash = new byte[20];
SHAHash = SHA1.GetHash(Message).Value;
// BigInteger values are represented in little endian
Array.Reverse(SHAHash);
// sure that a positive value is not incorrectly instantiated as a negative value
// by adding a byte whose value is zero to the end of the array
byte[] temp = new byte[SHAHash.Length];
Array.Copy(SHAHash, temp, SHAHash.Length);
SHAHash = new byte[temp.Length + 1];
Array.Copy(temp, SHAHash, temp.Length);
// convert hash array to BigInteger
BigInteger BI_Hash = new BigInteger(SHAHash);
if (BI_Hash > r)
{
MessageBox.Show("Error: Hash is greater than R.");
return;
}
// decimal representation of hash
tbHashDecimal.Text = BI_Hash.ToString();
//hexadecimal representation of hash
string hexHash = BI_Hash.ToString("X");
if (hexHash[0] == '0')
{
hexHash = hexHash.Substring(1);
}
tbHashHex.Text = hexHash;
// encrypt hash
string signature = RSA.EncryptHash(BI_Hash).ToString();
tbD.Text = RSA.D.ToString();
tbE.Text = RSA.E.ToString();
tbDigitalSignature.Text = signature;
// save signature to file
File.WriteAllText(FileName.Substring(0, FileName.IndexOf('.')) + "_Sign.txt", signature);
}
}
}
