private static RSACryptoServiceProvider DecodePrivateKeyInfo(byte[] pkcs8)
{
byte[] SeqOID = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
byte[] seq = new byte[15];
MemoryStream mem = new MemoryStream(pkcs8);
int lenstream = (int)mem.Length;
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;
bt = binr.ReadByte();
if (bt != 0x02)
return null;
twobytes = binr.ReadUInt16();
if (twobytes != 0x0001)
return null;
seq = binr.ReadBytes(15); //read the Sequence OID
if (!CompareBytearrays(seq, SeqOID)) //make sure Sequence for OID is correct
return null;
bt = binr.ReadByte();
if (bt != 0x04) //expect an Octet string
return null;
bt = binr.ReadByte(); //read next byte, or next 2 bytes is 0x81 or 0x82; otherwise bt is the byte count
if (bt == 0x81)
binr.ReadByte();
else
if (bt == 0x82)
binr.ReadUInt16();
//------ at this stage, the remaining sequence should be the RSA private key
byte[] rsaprivkey = binr.ReadBytes((int)(lenstream - mem.Position));
RSACryptoServiceProvider rsacsp = DecodeRSAPrivateKey(rsaprivkey);
return rsacsp;
}
catch (Exception)
{
return null;
}
finally { binr.Close(); }
}
