private static void VerifyDsaMessage()
{
//
// Load the Public Key
// X.509 Format
//
AsnKeyParser keyParser =
new AsnKeyParser("public.dsa.cs.key");
DSAParameters publicKey = keyParser.ParseDSAPublicKey();
//
// Initailize the CSP
//
CspParameters csp = new CspParameters();
// Cannot use PROV_DSS_DH
const int PROV_DSS = 3;
csp.ProviderType = PROV_DSS;
const int AT_SIGNATURE = 2;
csp.KeyNumber = AT_SIGNATURE;
csp.KeyContainerName = "DSA Test (OK to Delete)";
//
// Initialize the Provider
//
DSACryptoServiceProvider dsa =
new DSACryptoServiceProvider(csp);
dsa.PersistKeyInCsp = false;
//
// The moment of truth...
//
dsa.ImportParameters(publicKey);
//
// Load the message
// Message is m
//
byte[] message = null;
using (BinaryReader reader = new BinaryReader(
new FileStream("dsa.cs.msg", FileMode.Open, FileAccess.Read)))
{
FileInfo info = new FileInfo("dsa.cs.msg");
message = reader.ReadBytes((int)info.Length);
}
//
// Load the signature
// Signature is (r,s)
//
byte[] signature = null;
using (BinaryReader reader = new BinaryReader(
new FileStream("dsa.cs.sig", FileMode.Open, FileAccess.Read)))
{
FileInfo info = new FileInfo("dsa.cs.sig");
signature = reader.ReadBytes((int)info.Length);
}
//
// Compute h(m)
//
SHA1 sha = new SHA1CryptoServiceProvider();
byte[] hash = sha.ComputeHash(message);
//
// Initialize Verifier
//
DSASignatureDeformatter verifier =
new DSASignatureDeformatter(dsa);
verifier.SetHashAlgorithm("SHA1");
if (verifier.VerifySignature(hash, signature))
{
UTF8Encoding utf8 = new UTF8Encoding();
String s = utf8.GetString(message);
MessageBox.Show("Message Verified. Recovered String:\n" + s);
}
else
{
MessageBox.Show("Message Not Verified.");
}
// See http://blogs.msdn.com/tess/archive/2007/10/31/
// asp-net-crash-system-security-cryptography-cryptographicexception.aspx
dsa.Clear();
}
private static void SignDsaMessage()
{
//
// Load the Private Key
// PKCS#8 Format
//
AsnKeyParser keyParser =
new AsnKeyParser("private.dsa.cs.key");
DSAParameters privateKey = keyParser.ParseDSAPrivateKey();
//
// Initailize the CSP
// Supresses creation of a new key
//
CspParameters csp = new CspParameters();
csp.KeyContainerName = "DSA Test (OK to Delete)";
// Cannot use PROV_DSS_DH
const int PROV_DSS = 3;
csp.ProviderType = PROV_DSS;
const int AT_SIGNATURE = 2;
csp.KeyNumber = AT_SIGNATURE;
//
// Initialize the Provider
//
DSACryptoServiceProvider dsa =
new DSACryptoServiceProvider(csp);
dsa.PersistKeyInCsp = false;
//
// The moment of truth...
//
dsa.ImportParameters(privateKey);
//
// Sign the Message
//
DSASignatureFormatter signer =
new DSASignatureFormatter(dsa);
signer.SetHashAlgorithm("SHA1");
// The one and only
String m = "Crypto Interop: \u9aa8";
byte[] message = Encoding.GetEncoding("UTF-8").GetBytes(m);
// h(m)
SHA1 sha = new SHA1CryptoServiceProvider();
byte[] hash = sha.ComputeHash(message);
// Create the Signature for h(m)
byte[] signature = signer.CreateSignature(hash);
// Write the message
using (BinaryWriter writer = new BinaryWriter(
new FileStream("dsa.cs.msg", FileMode.Create,
FileAccess.ReadWrite)))
{
writer.Write(message);
}
// Write the signature on the message
using (BinaryWriter writer = new BinaryWriter(
new FileStream("dsa.cs.sig", FileMode.Create,
FileAccess.ReadWrite)))
{
writer.Write(signature);
}
// See http://blogs.msdn.com/tess/archive/2007/10/31/
// asp-net-crash-system-security-cryptography-cryptographicexception.aspx
dsa.Clear();
}
