Comment charger la clé publique RSA de fichier en C#

J'ai besoin de charger la suite de clé publique RSA à partir d'un fichier pour une utilisation avec le RSACryptoServiceProvider classe. Comment puis-je faire cela?

-----BEGIN PUBLIC KEY-----
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/syEKqEkMtQL0+d
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX+izR
KbGMRtur2TYklnyVkjeeHfAggo8vWQmWesnOG55vQYHbOOFoJbk0EkwEr5R/PbKm
byXPPN8zwnS5/XXXXXXXXXXXX
-----END PUBLIC KEY-----

---

Ce code fonctionne avec ma pub clés: http://www.jensign.com/opensslkey/

Voici le code, je suis en utilisant

        static string RSA(string input)
{
RSACryptoServiceProvider rsa = DecodeX509PublicKey(Convert.FromBase64String(GetKey()));
return (Convert.ToBase64String(rsa.Encrypt(Encoding.ASCII.GetBytes(input), false)));
}
static string GetKey()
{
return File.ReadAllText("master.pub").Replace("-----BEGIN PUBLIC KEY-----", "").Replace("-----END PUBLIC KEY-----", "");
//.Replace("\n", "");
}
private static bool CompareBytearrays(byte[] a, byte[] b)
{
if (a.Length != b.Length)
return false;
int i = 0;
foreach (byte c in a)
{
if (c != b[i])
return false;
i++;
}
return true;
}
public static RSACryptoServiceProvider DecodeX509PublicKey(byte[] x509key)
{
//encoded OID sequence for  PKCS #1 rsaEncryption szOID_RSA_RSA = "1.2.840.113549.1.1.1"
byte[] SeqOID = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
byte[] seq = new byte[15];
//---------  Set up stream to read the asn.1 encoded SubjectPublicKeyInfo blob  ------
MemoryStream mem = new MemoryStream(x509key);
BinaryReader binr = new BinaryReader(mem);    //wrap Memory Stream with BinaryReader for easy reading
byte bt = 0;
ushort twobytes = 0;
try
{
twobytes = binr.ReadUInt16();
if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
binr.ReadByte();    //advance 1 byte
else if (twobytes == 0x8230)
binr.ReadInt16();   //advance 2 bytes
else
return null;
seq = binr.ReadBytes(15);       //read the Sequence OID
if (!CompareBytearrays(seq, SeqOID))    //make sure Sequence for OID is correct
return null;
twobytes = binr.ReadUInt16();
if (twobytes == 0x8103) //data read as little endian order (actual data order for Bit String is 03 81)
binr.ReadByte();    //advance 1 byte
else if (twobytes == 0x8203)
binr.ReadInt16();   //advance 2 bytes
else
return null;
bt = binr.ReadByte();
if (bt != 0x00)     //expect null byte next
return null;
twobytes = binr.ReadUInt16();
if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
binr.ReadByte();    //advance 1 byte
else if (twobytes == 0x8230)
binr.ReadInt16();   //advance 2 bytes
else
return null;
twobytes = binr.ReadUInt16();
byte lowbyte = 0x00;
byte highbyte = 0x00;
if (twobytes == 0x8102) //data read as little endian order (actual data order for Integer is 02 81)
lowbyte = binr.ReadByte();  //read next bytes which is bytes in modulus
else if (twobytes == 0x8202)
{
highbyte = binr.ReadByte(); //advance 2 bytes
lowbyte = binr.ReadByte();
}
else
return null;
byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };   //reverse byte order since asn.1 key uses big endian order
int modsize = BitConverter.ToInt32(modint, 0);
byte firstbyte = binr.ReadByte();
binr.BaseStream.Seek(-1, SeekOrigin.Current);
if (firstbyte == 0x00)
{   //if first byte (highest order) of modulus is zero, don't include it
binr.ReadByte();    //skip this null byte
modsize -= 1;   //reduce modulus buffer size by 1
}
byte[] modulus = binr.ReadBytes(modsize);   //read the modulus bytes
if (binr.ReadByte() != 0x02)            //expect an Integer for the exponent data
return null;
int expbytes = (int)binr.ReadByte();        //should only need one byte for actual exponent data (for all useful values)
byte[] exponent = binr.ReadBytes(expbytes);
//------- create RSACryptoServiceProvider instance and initialize with public key -----
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSAParameters RSAKeyInfo = new RSAParameters();
RSAKeyInfo.Modulus = modulus;
RSAKeyInfo.Exponent = exponent;
RSA.ImportParameters(RSAKeyInfo);
return RSA;
}
catch (Exception)
{
return null;
}
finally { binr.Close(); }
}

Suffit d'appeler le " RSA " la méthode le texte que vous souhaitez crypter et vous avez terminé.