问题
I'm currently trying to implement a class to handle secure communications between instances of my app using RSACrytoServiceProveider class. First question : is it a good idea implement a single class to handle sender/reciever roles or should i split the roles into individual classes ?. This is what i have done so far:
using System;
using System.Text;
using System.Security.Cryptography;
namespace Agnus.Cipher
{
public class RSA
{
private byte[] plaintextBytes;
private byte[] ciphertextBytes;
private RSACryptoServiceProvider rSAProviderThis;
private RSACryptoServiceProvider rSAProviderOther;
public string PublicKey
{
get { return rSAProviderThis.ToXmlString(false); }
}
public RSA()
{
rSAProviderThis = new RSACryptoServiceProvider { PersistKeyInCsp = true };
plaintextBytes = Encoding.Unicode.GetBytes(PublicKey);
}
public void InitializeRSAProviderOther(string parameters)
{
rSAProviderOther.FromXmlString(parameters);
}
public byte[] Encrypt()
{
return rSAProviderThis.Encrypt(plaintextBytes, true);
}
public byte[] Decrypt()
{
return rSAProviderThis.Decrypt(ciphertextBytes, true);
}
public byte[] Sign()
{
using (SHA1Managed SHA1 = new SHA1Managed())
{
byte[] hash = SHA1.ComputeHash(ciphertextBytes);
byte[] signature = rSAProviderThis.SignHash(hash, CryptoConfig.MapNameToOID("SHA1"));
return signature;
}
}
public void Verify()
{
throw new NotImplementedException();
}
}
}
Second question : how do i send and receive data to be fed into the class ? i'm a green horn in this field, pointers would be appreciated.
回答1:
I would make the encrypt/sign/decrypt/verify methods take parameters for the data rather than having member variables for them. Having member variables for the key and provider seems okay though. Basically I'd expect to use the same key multiple times but not the same data.
I'd also make it immutable - make all the variables readonly, taking all the parameters you'll need for the providers in the constructor instead of having a separate initialisation method.
Beyond that, it seems okay to wrap the functionality in a simpler API for your needs though, yes.
回答2:
I have made some adjustments, here is what the implementation looks like:
using System;
using System.Security.Cryptography;
namespace Agnus.Cipher
{
public class RSA : IDisposable
{
private RSACryptoServiceProvider rSAProviderThis;
private RSACryptoServiceProvider rSAProviderOther = null;
public string PublicKey
{
get { return rSAProviderThis.ToXmlString(false); }
}
public RSA()
{
rSAProviderThis = new RSACryptoServiceProvider { PersistKeyInCsp = true };
}
public void InitializeRSAProviderOther(string parameters)
{
rSAProviderOther.FromXmlString(parameters);
}
public byte[] Encrypt(byte[] plaintextBytes)
{
return rSAProviderThis.Encrypt(plaintextBytes, true);
}
public string Decrypt(byte[] ciphertextBytes)
{
try
{
return Convert.ToBase64String( rSAProviderThis.Decrypt(ciphertextBytes, true));
}
catch (CryptographicException ex)
{
Console.WriteLine("Unable to decrypt: " + ex.Message + " " + ex.StackTrace);
}
finally
{
this.Dispose();
}
return string.Empty;
}
public string SignData(byte[] ciphertextBytes)
{
string signature = GenerateSignature(ciphertextBytes, rSAProviderThis);
return signature;
}
private string GenerateSignature(byte[] ciphertextBytes, RSACryptoServiceProvider provider)
{
using (SHA1Managed SHA1 = new SHA1Managed())
{
byte[] hash = SHA1.ComputeHash(ciphertextBytes);
string signature = Convert.ToBase64String(provider.SignHash(hash, CryptoConfig.MapNameToOID("SHA1")));
return signature;
}
}
public string VerifySignature(byte[] ciphertextBytes, string parameters, string signatureToVerify)
{
InitializeRSAProviderOther(parameters);
string actualSignature = GenerateSignature(ciphertextBytes, rSAProviderOther);
if (actualSignature.Equals(signatureToVerify))
{
//verification successful
string decryptedData = this.Decrypt(ciphertextBytes);
return decryptedData;
//decryptedData is a symmetric key
}
else
{
//verification unsuccessful
//end session
}
return string.Empty;
}
#region IDisposable Members
public void Dispose()
{
if (rSAProviderOther != null)
{
rSAProviderOther.Clear();
}
rSAProviderThis.Clear();
GC.SuppressFinalize(this);
}
#endregion
}
}
you guys still haven't said anything about how communication is going to be established (i'm thinking sockets). Please enlighten me.
回答3:
I don't know if this snip of code may help you, I've wrote this code to be able to crypt and decrypt with private/public key pairs in diverse crypting algortims and without data to encrypt length issue, infact RSA implementation in .NET suffer whe you try to manage more than 250 (more or less, sorry I don't recall) bytes of data.
I just cut and paste only methods needed, I also cutted xml documentation cause is not in english, if you found this useful let me know, I can post all source. I repeat I do not tested this cut&paste version, but I used the full version of this class that is not that different.
BTW: it's in VB, but if you just need to lurk at it I think it's enough ;)
Namespace Crypto
Public Class RSACry
Shared Sub New()
End Sub
Public Enum Algorithms
DES
TDES
RC2
RDAEL
End Enum
Public Shared Function Encrypt(ByVal xmlkeystring As String, ByVal typo As Algorithms, ByVal datatoencrypt As String) As String
Dim rsaer As RSA = Crypto.RSACry.ReadKeyString(xmlkeystring)
Dim result() As Byte = Crypto.RSACry.EncryptIt(rsaer, typo, datatoencrypt)
Return System.Convert.ToBase64String(result)
End Function
Public Shared Function Decrypt(ByVal xmlkeystring As String, ByVal typo As Algorithms, ByVal datatodecrypt As String) As String
Dim rsaer As RSA = Crypto.RSACry.ReadKeyString(xmlkeystring)
Dim result() As Byte = Crypto.RSACry.DecryptIt(rsaer, typo, datatodecrypt)
Return System.Text.Encoding.UTF8.GetString(result)
End Function
Friend Shared Function EncryptIt(ByRef rsaer As RSA, ByVal typo As Algorithms, ByVal datatoencrypt As String) As Byte()
Dim result() As Byte = Nothing
Try
Dim plainbytes() As Byte = System.Text.Encoding.UTF8.GetBytes(datatoencrypt)
Dim sa As SymmetricAlgorithm = SymmetricAlgorithm.Create(Crypto.RSACry.GetAlgorithmName(typo))
Dim ct As ICryptoTransform = sa.CreateEncryptor()
Dim encrypt() As Byte = ct.TransformFinalBlock(plainbytes, 0, plainbytes.Length)
Dim fmt As RSAPKCS1KeyExchangeFormatter = New RSAPKCS1KeyExchangeFormatter(rsaer)
Dim keyex() As Byte = fmt.CreateKeyExchange(sa.Key)
--return the key exchange, the IV (public) and encrypted data
result = New Byte(keyex.Length + sa.IV.Length + encrypt.Length) {}
Buffer.BlockCopy(keyex, 0, result, 0, keyex.Length)
Buffer.BlockCopy(sa.IV, 0, result, keyex.Length, sa.IV.Length)
Buffer.BlockCopy(encrypt, 0, result, keyex.Length + sa.IV.Length, encrypt.Length)
Catch ex As Exception
Throw New CryptographicException("Unable to crypt: " + ex.Message)
End Try
Return result
End Function
Friend Shared Function DecryptIt(ByRef rsaer As RSA, ByVal typo As Algorithms, ByVal datatodecrypt As String) As Byte()
Dim result() As Byte = Nothing
Try
Dim encrbytes() As Byte = System.Convert.FromBase64String(datatodecrypt)
Dim sa As SymmetricAlgorithm = SymmetricAlgorithm.Create(Crypto.RSACry.GetAlgorithmName(typo))
Dim keyex() As Byte = New Byte((rsaer.KeySize >> 3) - 1) {}
Buffer.BlockCopy(encrbytes, 0, keyex, 0, keyex.Length)
Dim def As RSAPKCS1KeyExchangeDeformatter = New RSAPKCS1KeyExchangeDeformatter(rsaer)
Dim key() As Byte = def.DecryptKeyExchange(keyex)
Dim iv() As Byte = New Byte((sa.IV.Length - 1)) {}
Buffer.BlockCopy(encrbytes, keyex.Length, iv, 0, iv.Length)
Dim ct As ICryptoTransform = sa.CreateDecryptor(key, iv)
result = ct.TransformFinalBlock(encrbytes, keyex.Length + iv.Length, (encrbytes.Length - 1) - (keyex.Length + iv.Length))
Catch ex As Exception
Throw New CryptographicException("Unable to decrypt: " + ex.Message)
End Try
Return result
End Function
Friend Shared Function GetAlgorithmName(ByVal typo As Algorithms) As String
Dim algtype As String = String.Empty
Select Case typo
Case Algorithms.DES
Return "DES"
Exit Select
Case Algorithms.RC2
Return "RC2"
Exit Select
Case Algorithms.RDAEL
Return "Rijndael"
Exit Select
Case Algorithms.TDES
Return "TripleDES"
Exit Select
Case Else
Return "Rijndael"
Exit Select
End Select
Return algtype
End Function
Friend Shared Function ReadKeyString(ByVal xmlkeystring As String) As RSA
Dim rsaer As RSA = Nothing
Try
If (String.IsNullOrEmpty(xmlkeystring)) Then Throw New Exception("Key is not specified")
rsaer = RSA.Create()
rsaer.FromXmlString(xmlkeystring)
Catch ex As Exception
Throw New CryptographicException("Unable to load key")
End Try
Return rsaer
End Function
End Namespace
回答4:
@gogole: actually I don't use sockets, this code is used in stand alone way with keys hand-bringed. However once you have your crypt mechanism, you're at more than half of the journey.
Here there are two missing methods to create keys, as you requested the code is complete. I hope you found this helpful
Public Shared Sub CreateKeyPair(ByVal filename As String)
Dim xmlpublic As String = String.Empty
Dim xmlprivate As String = String.Empty
CreateKeyPair(xmlpublic, xmlprivate)
Try
Dim writer As New StreamWriter(filename + ".prv")
writer.Write(xmlprivate)
writer.Flush()
writer.Close()
Catch ex As Exception
Throw New CryptographicException("Unable to write private key file: " + ex.Message)
End Try
Try
Dim writer = New StreamWriter(filename + ".pub")
writer.Write(xmlpublic)
writer.Flush()
writer.Close()
Catch ex As Exception
Throw New CryptographicException("Unable to write public key file: " + ex.Message)
End Try
End Sub
Public Shared Sub CreateKeyPair(ByRef xmlpublic As String, ByRef xmlprivate As String)
Dim rsa As RSA = Nothing
Try
rsa.Create()
Catch ex As Exception
Throw New CryptographicException("Unable to initialize keys: " + ex.Message)
End Try
Try
xmlpublic = rsa.ToXmlString(True)
Catch ex As Exception
Throw New CryptographicException("Unable to generate public key: " + ex.Message)
End Try
Try
xmlprivate = rsa.ToXmlString(False)
Catch ex As Exception
Throw New CryptographicException("Unable to generate private key: " + ex.Message)
End Try
End Sub
回答5:
Does not know much vb but tried to convert @Andrea Celin one of useful Code in c#
namespace Crypto
{
using System;
using System.Security.Cryptography;
class RSACry
{
public enum Algorithms
{
DES,
TDES,
RC2,
RDAEL
};
public string Encrypt(string xmlkeystring, Algorithms typo, string datatoencrypt)
{
RSA rsaer = RSACry.ReadKeyString(xmlkeystring);
byte[] result = RSACry.EncryptIt(rsaer, typo, datatoencrypt);
return System.Convert.ToBase64String(result);
}
public string Decrypt(string xmlkeystring,Algorithms typo,string datatodecrypt)
{
RSA rsaer = RSACry.ReadKeyString(xmlkeystring);
byte[] result =RSACry.DecryptIt(rsaer, typo, datatodecrypt);
return System.Text.Encoding.UTF8.GetString(result);
}
public static byte[] EncryptIt(RSA rsaer, Algorithms typo, string datatoencrypt)
{
byte[] result = null;
try
{
byte[] plainbytes = System.Text.Encoding.UTF8.GetBytes(datatoencrypt);
SymmetricAlgorithm sa = SymmetricAlgorithm.Create(RSACry.GetAlgorithmName(typo));
ICryptoTransform ct = sa.CreateEncryptor();
byte[] encrypt = ct.TransformFinalBlock(plainbytes, 0, plainbytes.Length);
RSAPKCS1KeyExchangeFormatter fmt = new RSAPKCS1KeyExchangeFormatter(rsaer);
byte[] keyex = fmt.CreateKeyExchange(sa.Key);
//--return the key exchange, the IV (public) and encrypted data
result = new byte[keyex.Length + sa.IV.Length + encrypt.Length];
Buffer.BlockCopy(keyex, 0, result, 0, keyex.Length);
Buffer.BlockCopy(sa.IV, 0, result, keyex.Length, sa.IV.Length);
Buffer.BlockCopy(encrypt, 0, result, keyex.Length + sa.IV.Length, encrypt.Length);
}
catch (Exception ex)
{
throw new CryptographicException("Unable to crypt: " + ex.Message);
}
return result;
}
public static byte[] DecryptIt(RSA rsaer, Algorithms typo, string datatodecrypt)
{
byte[] result = null;
try
{
byte[] encrbytes = System.Convert.FromBase64String(datatodecrypt);
SymmetricAlgorithm sa = SymmetricAlgorithm.Create(RSACry.GetAlgorithmName(typo));
byte[] keyex = new byte[(rsaer.KeySize >> 3) - 1];
Buffer.BlockCopy(encrbytes, 0, keyex, 0, keyex.Length);
RSAPKCS1KeyExchangeDeformatter def = new RSAPKCS1KeyExchangeDeformatter(rsaer);
byte[] key = def.DecryptKeyExchange(keyex);
byte[] iv = new byte[sa.IV.Length - 1];
Buffer.BlockCopy(encrbytes, keyex.Length, iv, 0, iv.Length);
ICryptoTransform ct = sa.CreateDecryptor(key, iv);
result = ct.TransformFinalBlock(encrbytes, keyex.Length + iv.Length, (encrbytes.Length - 1) - (keyex.Length + iv.Length));
}
catch (Exception ex)
{
throw new CryptographicException("Unable to decrypt: " + ex.Message);
}
return result;
}
public static string GetAlgorithmName(Algorithms typo)
{
string algtype = String.Empty;
switch(typo)
{
case Algorithms.DES:
algtype = "DES";
break;
case Algorithms.RC2:
algtype = "RC2";
break;
case Algorithms.RDAEL:
algtype = "Rijndael";
break;
case Algorithms.TDES:
algtype = "TripleDES";
break;
default:
algtype = "Rijndael";
break;
}
return algtype;
}
public static RSA ReadKeyString(string xmlkeystring)
{
RSA rsaer = null;
try
{
if (String.IsNullOrEmpty(xmlkeystring))
{ throw new Exception("Key is not specified"); }
rsaer = RSA.Create();
rsaer.FromXmlString(xmlkeystring);
}
catch (Exception ex)
{
throw new CryptographicException("Unable to load key :"+ex.Message);
}
return rsaer;
}
}
}
来源：https://stackoverflow.com/questions/384401/implementing-rsa-in-c-sharp