我有一个System.Security.Cryptography.RSACryptoServiceProvider的实例,我需要将它的密钥导出到PEM字符串- 像这样:
-----BEGIN RSA PRIVATE KEY----- MIICXAIBAAKBgQDUNPB6Lvx+tlP5QhSikADl71AjZf9KN31qrDpXNDNHEI0OTVJ1 OaP2l56bSKNo8trFne1NK/B4JzCuNP8x6oGCAG+7bFgkbTMzV2PCoDCRjNH957Q4 Gxgx1VoS6PjD3OigZnx5b9Hebbp3OrTuqNZaK/oLPGr5swxHILFVeHKupQIDAQAB AoGAQk3MOZEGyZy0fjQ8eFKgRTfSBU1wR8Mwx6zKicbAotq0CBz2v7Pj3D+higlX LYp7+rUOmUc6WoB8QGJEvlb0YZVxUg1yDLMWYPE7ddsHsOkBIs7zIyS6cqhn0yZD VTRFjVST/EduvpUOL5hbyLSwuq+rbv0iPwGW5hkCHNEhx2ECQQDfLS5549wjiFXF gcio8g715eMT+20we3YmgMJDcviMGwN/mArvnBgBQsFtCTsMoOxm68SfIrBYlKYy BsFxn+19AkEA82q83pmcbGJRJ3ZMC/Pv+/+/XNFOvMkfT9qbuA6Lv69Z1yk7I1ie FTH6tOmPUu4WsIOFtDuYbfV2pvpqx7GuSQJAK3SnvRIyNjUAxoF76fGgGh9WNPjb DPqtSdf+e5Wycc18w+Z+EqPpRK2T7kBC4DWhcnTsBzSA8+6V4d3Q4ugKHQJATRhw a3xxm65kD8CbA2omh0UQQgCVFJwKy8rsaRZKUtLh/JC1h1No9kOXKTeUSmrYSt3N OjFp7OHCy84ihc8T6QJBANe+9xkN9hJYNK1pL1kSwXNuebzcgk3AMwHh7ThvjLgO jruxbM2NyMM5tl9NZCgh1vKc2v5VaonqM1NBQPDeTTw= -----END RSA PRIVATE KEY-----
但是根据MSDN文档,没有这种选择,只有某种XML导出。我不能使用BouncyCastle之类的任何第三方库。有什么方法可以产生这个字串吗?
请注意:以下代码用于导出 私钥 。如果您要导出 公共 密钥,请参考我在此处给出的答案。
PEM格式只是转换为Base64 的密钥(按PKCS#1)的ASN.1 DER编码。鉴于表示密钥所需的字段数量有限,创建快捷的DER编码器以输出适当的格式然后进行Base64编码非常简单。因此,下面的代码并不是特别优雅,但是可以做到:
private static void ExportPrivateKey(RSACryptoServiceProvider csp, TextWriter outputStream) { if (csp.PublicOnly) throw new ArgumentException("CSP does not contain a private key", "csp"); var parameters = csp.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); EncodeIntegerBigEndian(innerWriter, new byte[] { 0x00 }); // Version EncodeIntegerBigEndian(innerWriter, parameters.Modulus); EncodeIntegerBigEndian(innerWriter, parameters.Exponent); EncodeIntegerBigEndian(innerWriter, parameters.D); EncodeIntegerBigEndian(innerWriter, parameters.P); EncodeIntegerBigEndian(innerWriter, parameters.Q); EncodeIntegerBigEndian(innerWriter, parameters.DP); EncodeIntegerBigEndian(innerWriter, parameters.DQ); EncodeIntegerBigEndian(innerWriter, parameters.InverseQ); 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(); outputStream.WriteLine("-----BEGIN RSA PRIVATE KEY-----"); // Output as Base64 with lines chopped at 64 characters for (var i = 0; i < base64.Length; i += 64) { outputStream.WriteLine(base64, i, Math.Min(64, base64.Length - i)); } outputStream.WriteLine("-----END RSA PRIVATE KEY-----"); } } 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)); } } } private static void EncodeIntegerBigEndian(BinaryWriter stream, byte[] value, bool forceUnsigned = true) { stream.Write((byte)0x02); // INTEGER var prefixZeros = 0; for (var i = 0; i < value.Length; i++) { if (value[i] != 0) break; prefixZeros++; } if (value.Length - prefixZeros == 0) { EncodeLength(stream, 1); stream.Write((byte)0); } else { if (forceUnsigned && value[prefixZeros] > 0x7f) { // Add a prefix zero to force unsigned if the MSB is 1 EncodeLength(stream, value.Length - prefixZeros + 1); stream.Write((byte)0); } else { EncodeLength(stream, value.Length - prefixZeros); } for (var i = prefixZeros; i < value.Length; i++) { stream.Write(value[i]); } } }