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)); } } } } }