starting working on RSA

This commit is contained in:
Nicolas Constant 2020-03-21 04:33:51 -04:00
parent de09dfbfc4
commit 6be59fc867
No known key found for this signature in database
GPG key ID: 1E9F677FB01A5688
2 changed files with 99 additions and 8 deletions

View file

@ -1,8 +0,0 @@
using System;
namespace BirdsiteLive.Cryptography
{
public class Class1
{
}
}

View file

@ -0,0 +1,99 @@
using System;
using System.IO;
using System.Security.Cryptography;
namespace BirdsiteLive.Cryptography
{
//https://gist.github.com/ststeiger/f4b29a140b1e3fd618679f89b7f3ff4a
//https://gist.github.com/valep27/4a720c25b35fff83fbf872516f847863
//https://gist.github.com/therightstuff/aa65356e95f8d0aae888e9f61aa29414
//https://stackoverflow.com/questions/52468125/export-rsa-public-key-in-der-format-and-decrypt-data
public class RsaGenerator
{
public string GetRsa()
{
var rsa = RSA.Create();
var outputStream = new StringWriter();
var parameters = rsa.ExportParameters(true);
using (var stream = new MemoryStream())
{
var writer = new BinaryWriter(stream);
writer.Write((byte)0x30); // SEQUENCE
using (var innerStream = new MemoryStream())
{
var innerWriter = new BinaryWriter(innerStream);
innerWriter.Write((byte)0x30); // SEQUENCE
EncodeLength(innerWriter, 13);
innerWriter.Write((byte)0x06); // OBJECT IDENTIFIER
var rsaEncryptionOid = new byte[] { 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01 };
EncodeLength(innerWriter, rsaEncryptionOid.Length);
innerWriter.Write(rsaEncryptionOid);
innerWriter.Write((byte)0x05); // NULL
EncodeLength(innerWriter, 0);
innerWriter.Write((byte)0x03); // BIT STRING
using (var bitStringStream = new MemoryStream())
{
var bitStringWriter = new BinaryWriter(bitStringStream);
bitStringWriter.Write((byte)0x00); // # of unused bits
bitStringWriter.Write((byte)0x30); // SEQUENCE
using (var paramsStream = new MemoryStream())
{
var paramsWriter = new BinaryWriter(paramsStream);
EncodeIntegerBigEndian(paramsWriter, parameters.Modulus); // Modulus
EncodeIntegerBigEndian(paramsWriter, parameters.Exponent); // Exponent
var paramsLength = (int)paramsStream.Length;
EncodeLength(bitStringWriter, paramsLength);
bitStringWriter.Write(paramsStream.GetBuffer(), 0, paramsLength);
}
var bitStringLength = (int)bitStringStream.Length;
EncodeLength(innerWriter, bitStringLength);
innerWriter.Write(bitStringStream.GetBuffer(), 0, bitStringLength);
}
var length = (int)innerStream.Length;
EncodeLength(writer, length);
writer.Write(innerStream.GetBuffer(), 0, length);
}
var base64 = Convert.ToBase64String(stream.GetBuffer(), 0, (int)stream.Length).ToCharArray();
// WriteLine terminates with \r\n, we want only \n
outputStream.Write("-----BEGIN PUBLIC KEY-----\n");
for (var i = 0; i < base64.Length; i += 64)
{
outputStream.Write(base64, i, Math.Min(64, base64.Length - i));
outputStream.Write("\n");
}
outputStream.Write("-----END PUBLIC KEY-----");
}
return outputStream.ToString();
}
private static void EncodeLength(BinaryWriter stream, int length)
{
if (length < 0) throw new ArgumentOutOfRangeException("length", "Length must be non-negative");
if (length < 0x80)
{
// Short form
stream.Write((byte)length);
}
else
{
// Long form
var temp = length;
var bytesRequired = 0;
while (temp > 0)
{
temp >>= 8;
bytesRequired++;
}
stream.Write((byte)(bytesRequired | 0x80));
for (var i = bytesRequired - 1; i >= 0; i--)
{
stream.Write((byte)(length >> (8 * i) & 0xff));
}
}
}
}
}