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Import and export RSA Keys between C# and PEM format using BouncyCastle
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| usingOrg.BouncyCastle.Crypto; | |
| usingOrg.BouncyCastle.Crypto.Parameters; | |
| usingOrg.BouncyCastle.OpenSsl; | |
| usingOrg.BouncyCastle.Security; | |
| usingSystem; | |
| usingSystem.IO; | |
| usingSystem.Security.Cryptography; | |
| namespaceMyProject.Data.Encryption | |
| { | |
| publicclassRSAKeys | |
| { | |
| /// <summary> | |
| /// Import OpenSSH PEM private key string into MS RSACryptoServiceProvider | |
| /// </summary> | |
| /// <param name="pem"></param> | |
| /// <returns></returns> | |
| publicstaticRSACryptoServiceProviderImportPrivateKey(stringpem){ | |
| PemReaderpr=newPemReader(newStringReader(pem)); | |
| AsymmetricCipherKeyPairKeyPair=(AsymmetricCipherKeyPair)pr.ReadObject(); | |
| RSAParametersrsaParams=DotNetUtilities.ToRSAParameters((RsaPrivateCrtKeyParameters)KeyPair.Private); | |
| RSACryptoServiceProvidercsp=newRSACryptoServiceProvider();// cspParams); | |
| csp.ImportParameters(rsaParams); | |
| returncsp; | |
| } | |
| /// <summary> | |
| /// Import OpenSSH PEM public key string into MS RSACryptoServiceProvider | |
| /// </summary> | |
| /// <param name="pem"></param> | |
| /// <returns></returns> | |
| publicstaticRSACryptoServiceProviderImportPublicKey(stringpem){ | |
| PemReaderpr=newPemReader(newStringReader(pem)); | |
| AsymmetricKeyParameterpublicKey=(AsymmetricKeyParameter)pr.ReadObject(); | |
| RSAParametersrsaParams=DotNetUtilities.ToRSAParameters((RsaKeyParameters)publicKey); | |
| RSACryptoServiceProvidercsp=newRSACryptoServiceProvider();// cspParams); | |
| csp.ImportParameters(rsaParams); | |
| returncsp; | |
| } | |
| /// <summary> | |
| /// Export private (including public) key from MS RSACryptoServiceProvider into OpenSSH PEM string | |
| /// slightly modified from https://stackoverflow.com/a/23739932/2860309 | |
| /// </summary> | |
| /// <param name="csp"></param> | |
| /// <returns></returns> | |
| publicstaticstringExportPrivateKey(RSACryptoServiceProvidercsp) | |
| { | |
| StringWriteroutputStream=newStringWriter(); | |
| if(csp.PublicOnly)thrownewArgumentException("CSP does not contain a private key","csp"); | |
| varparameters=csp.ExportParameters(true); | |
| using(varstream=newMemoryStream()) | |
| { | |
| varwriter=newBinaryWriter(stream); | |
| writer.Write((byte)0x30);// SEQUENCE | |
| using(varinnerStream=newMemoryStream()) | |
| { | |
| varinnerWriter=newBinaryWriter(innerStream); | |
| EncodeIntegerBigEndian(innerWriter,newbyte[]{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); | |
| varlength=(int)innerStream.Length; | |
| EncodeLength(writer,length); | |
| writer.Write(innerStream.GetBuffer(),0,length); | |
| } | |
| varbase64=Convert.ToBase64String(stream.GetBuffer(),0,(int)stream.Length).ToCharArray(); | |
| // WriteLine terminates with \r\n, we want only \n | |
| outputStream.Write("-----BEGIN RSA PRIVATE KEY-----\n"); | |
| // Output as Base64 with lines chopped at 64 characters | |
| for(vari=0;i<base64.Length;i+=64) | |
| { | |
| outputStream.Write(base64,i,Math.Min(64,base64.Length-i)); | |
| outputStream.Write("\n"); | |
| } | |
| outputStream.Write("-----END RSA PRIVATE KEY-----"); | |
| } | |
| returnoutputStream.ToString(); | |
| } | |
| /// <summary> | |
| /// Export public key from MS RSACryptoServiceProvider into OpenSSH PEM string | |
| /// slightly modified from https://stackoverflow.com/a/28407693 | |
| /// </summary> | |
| /// <param name="csp"></param> | |
| /// <returns></returns> | |
| publicstaticstringExportPublicKey(RSACryptoServiceProvidercsp) | |
| { | |
| StringWriteroutputStream=newStringWriter(); | |
| varparameters=csp.ExportParameters(false); | |
| using(varstream=newMemoryStream()) | |
| { | |
| varwriter=newBinaryWriter(stream); | |
| writer.Write((byte)0x30);// SEQUENCE | |
| using(varinnerStream=newMemoryStream()) | |
| { | |
| varinnerWriter=newBinaryWriter(innerStream); | |
| innerWriter.Write((byte)0x30);// SEQUENCE | |
| EncodeLength(innerWriter,13); | |
| innerWriter.Write((byte)0x06);// OBJECT IDENTIFIER | |
| varrsaEncryptionOid=newbyte[]{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(varbitStringStream=newMemoryStream()) | |
| { | |
| varbitStringWriter=newBinaryWriter(bitStringStream); | |
| bitStringWriter.Write((byte)0x00);// # of unused bits | |
| bitStringWriter.Write((byte)0x30);// SEQUENCE | |
| using(varparamsStream=newMemoryStream()) | |
| { | |
| varparamsWriter=newBinaryWriter(paramsStream); | |
| EncodeIntegerBigEndian(paramsWriter,parameters.Modulus);// Modulus | |
| EncodeIntegerBigEndian(paramsWriter,parameters.Exponent);// Exponent | |
| varparamsLength=(int)paramsStream.Length; | |
| EncodeLength(bitStringWriter,paramsLength); | |
| bitStringWriter.Write(paramsStream.GetBuffer(),0,paramsLength); | |
| } | |
| varbitStringLength=(int)bitStringStream.Length; | |
| EncodeLength(innerWriter,bitStringLength); | |
| innerWriter.Write(bitStringStream.GetBuffer(),0,bitStringLength); | |
| } | |
| varlength=(int)innerStream.Length; | |
| EncodeLength(writer,length); | |
| writer.Write(innerStream.GetBuffer(),0,length); | |
| } | |
| varbase64=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(vari=0;i<base64.Length;i+=64) | |
| { | |
| outputStream.Write(base64,i,Math.Min(64,base64.Length-i)); | |
| outputStream.Write("\n"); | |
| } | |
| outputStream.Write("-----END PUBLIC KEY-----"); | |
| } | |
| returnoutputStream.ToString(); | |
| } | |
| /// <summary> | |
| /// https://stackoverflow.com/a/23739932/2860309 | |
| /// </summary> | |
| /// <param name="stream"></param> | |
| /// <param name="length"></param> | |
| privatestaticvoidEncodeLength(BinaryWriterstream,intlength) | |
| { | |
| if(length<0)thrownewArgumentOutOfRangeException("length","Length must be non-negative"); | |
| if(length<0x80) | |
| { | |
| // Short form | |
| stream.Write((byte)length); | |
| } | |
| else | |
| { | |
| // Long form | |
| vartemp=length; | |
| varbytesRequired=0; | |
| while(temp>0) | |
| { | |
| temp>>=8; | |
| bytesRequired++; | |
| } | |
| stream.Write((byte)(bytesRequired|0x80)); | |
| for(vari=bytesRequired-1;i>=0;i--) | |
| { | |
| stream.Write((byte)(length>>(8*i)&0xff)); | |
| } | |
| } | |
| } | |
| /// <summary> | |
| /// https://stackoverflow.com/a/23739932/2860309 | |
| /// </summary> | |
| /// <param name="stream"></param> | |
| /// <param name="value"></param> | |
| /// <param name="forceUnsigned"></param> | |
| privatestaticvoidEncodeIntegerBigEndian(BinaryWriterstream,byte[]value,boolforceUnsigned=true) | |
| { | |
| stream.Write((byte)0x02);// INTEGER | |
| varprefixZeros=0; | |
| for(vari=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(vari=prefixZeros;i<value.Length;i++) | |
| { | |
| stream.Write(value[i]); | |
| } | |
| } | |
| } | |
| } | |
| } |
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