Develop Reference

Use public Rsa key in C# [duplicate]

I'm currently trying to create an RSACryptoServiceProvider object solely from a decoded PEM file. After several days of searching, I did manage to wrangle a working solution but it's not one that would be production ready.
In a nutshell, in order to create an RSACryptoServiceProvider object from the bytes that make up the public key in a PEM file, I must create the object specifying the keysize (currently 2048 using SHA256, specifically) and then importing a RSAParameters object with the Exponent and Modulus set. I'm doing this as so;
byte[] publicKeyBytes = Convert.FromBase64String(deserializedPublicKey.Replace("-----BEGIN PUBLIC KEY-----", "")
.Replace("-----END PUBLIC KEY-----", ""));
// extract the modulus and exponent based on the key data
byte[] exponentData = new byte[3];
byte[] modulusData = new byte[256];
Array.Copy(publicKeyBytes, publicKeyBytes.Length - exponentData.Length, exponentData, 0, exponentData.Length);
Array.Copy(publicKeyBytes, 9, modulusData, 0, modulusData.Length);
// import the public key data (base RSA - works)
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(dwKeySize: 2048);
RSAParameters rsaParam = rsa.ExportParameters(false);
rsaParam.Modulus = modulusData;
rsaParam.Exponent = exponentData;
rsa.ImportParameters(rsaParam);
While this works, it's not viable to assume that the deserializedPublicKey will be exactly 270 bytes and that the modulus I need is found at position 9 and always be 256 bytes in length.
How do I change this to correctly pick out the Modulus and Exponent byte given a set of public key bytes? I've tried to make sense of the ASN.1 standard but with little luck finding what I need from it - the standard(s) are somewhat byzantine.
Any help is appreciated.

You don't need to export existing parameters then re-import over top of them. That forces your machine to generate an RSA key then throw it away. So specifying a keysize to the constructor doesn't matter (if you don't use the key it won't generate one... usually).
The public key file is a DER encoded blob.
-----BEGIN PUBLIC KEY-----
MIGgMA0GCSqGSIb3DQEBAQUAA4GOADCBigKBggC8rLGlNJ17NaWArDs5mOsV6/kA
7LMpvx91cXoAshmcihjXkbWSt+xSvVry2w07Y18FlXU9/3unyYctv34yJt70SgfK
Vo0QF5ksK0G/5ew1cIJM8fSxWRn+1RP9pWIEryA0otCP8EwsyknRaPoD+i+jL8zT
SEwV8KLlRnx2/HYLVQkCAwEAAQ==
-----END PUBLIC KEY-----
If you take the contents inside the PEM armor, it's a Base64-encoded byte array.
30 81 A0 30 0D 06 09 2A 86 48 86 F7 0D 01 01 01
05 00 03 81 8E 00 30 81 8A 02 81 82 00 BC AC B1
A5 34 9D 7B 35 A5 80 AC 3B 39 98 EB 15 EB F9 00
EC B3 29 BF 1F 75 71 7A 00 B2 19 9C 8A 18 D7 91
B5 92 B7 EC 52 BD 5A F2 DB 0D 3B 63 5F 05 95 75
3D FF 7B A7 C9 87 2D BF 7E 32 26 DE F4 4A 07 CA
56 8D 10 17 99 2C 2B 41 BF E5 EC 35 70 82 4C F1
F4 B1 59 19 FE D5 13 FD A5 62 04 AF 20 34 A2 D0
8F F0 4C 2C CA 49 D1 68 FA 03 FA 2F A3 2F CC D3
48 4C 15 F0 A2 E5 46 7C 76 FC 76 0B 55 09 02 03
01 00 01
ITU-T X.690 defines how to read things encoded under Basic Encoding Rules (BER), Canonical Encoding Rules (CER, which I've never seen explicitly used), and Distinguished Encoding Rules (DER). For the most part CER restricts BER and DER restricts CER, making DER the easiest to read. (ITU-T X.680 describes Abstract Syntax Notation One (ASN.1), which is the grammar that DER is a binary encoding for)
We can do a bit of parsing now:
30
This identifies a SEQUENCE (0x10) with the CONSTRUCTED bit set (0x20), which means that it contains other DER/tagged values. (SEQUENCE is always CONSTRUCTED in DER)
81 A0
This next part is a length. Since it has the high bit set (> 0x7F) the first byte is a "length length" value. It indicates that the true length is encoded in the next 1 byte(s) (lengthLength & 0x7F). Therefore the contents of this SEQUENCE are 160 bytes total. (In this case, "the rest of the data", but the SEQUENCE could have been contained within something else). So let's read the contents:
30 0D
We see our CONSTRUCTED SEQUENCE again (0x30), with a length value of 0x0D, so we have a 13 byte payload.
06 09 2A 86 48 86 F7 0D 01 01 01 05 00
The 06 is OBJECT IDENTIFIER, with a 0x09 byte payload. OID has a slightly non-intuitive encoding, but this one is equivalent to the text representation 1.2.840.113549.1.1.1, which is id-rsaEncryption (http://www.oid-info.com/get/1.2.840.113549.1.1.1).
This still leaves us with two bytes (05 00) which we see is a NULL (with a 0 byte payload, because, well, it's NULL).
So so far we have
SEQUENCE
SEQUENCE
OID 1.2.840.113549.1.1.1
NULL
143 more bytes.
Continuing on:
03 81 8E 00
The 03 means BIT STRING. BIT STRING is encoded as [tag] [length] [number of unused bits]. The unused bits is essentially always zero. So this is a sequence of bits, 0x8E bytes long, and all of them are used.
Technically we should stop there, because CONSTRUCTED wasn't set. But since we happen to know the format of this structure, we treat the value as if the CONSTRUCTED bit was set anyways:
30 81 8A
Here's our friend CONSTRUCTED SEQUENCE again, 0x8A payload bytes, which conveniently corresponds to "everything that's left".
02 81 82
02 identifies an INTEGER, and this one has 0x82 payload bytes:
00 BC AC B1 A5 34 9D 7B 35 A5 80 AC 3B 39 98 EB
15 EB F9 00 EC B3 29 BF 1F 75 71 7A 00 B2 19 9C
8A 18 D7 91 B5 92 B7 EC 52 BD 5A F2 DB 0D 3B 63
5F 05 95 75 3D FF 7B A7 C9 87 2D BF 7E 32 26 DE
F4 4A 07 CA 56 8D 10 17 99 2C 2B 41 BF E5 EC 35
70 82 4C F1 F4 B1 59 19 FE D5 13 FD A5 62 04 AF
20 34 A2 D0 8F F0 4C 2C CA 49 D1 68 FA 03 FA 2F
A3 2F CC D3 48 4C 15 F0 A2 E5 46 7C 76 FC 76 0B
55 09
The leading 0x00 would be a violation of DER, except the next byte has the high bit set. This means that the 0x00 was there to keep the sign bit from being set, making this a positive number.
02 03 01 00 01
Another INTEGER, 3 bytes, value 01 00 01. And we're done.
SEQUENCE
SEQUENCE
OID 1.2.840.113549.1.1.1
NULL
BIT STRING
SEQUENCE
INTEGER 00 BC AC ... 0B 55 09
INTEGER 01 00 01
Harvesting https://www.rfc-editor.org/rfc/rfc5280 we see that this looks a lot like a SubjectPublicKeyInfo structure:
SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING }
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL }
-- contains a value of the type
-- registered for use with the
-- algorithm object identifier value
Of course, it doesn't know what the RSA public key format is. But the oid-info site told us to check out RFC 2313, where we see
An RSA public key shall have ASN.1 type RSAPublicKey:
RSAPublicKey ::= SEQUENCE {
modulus INTEGER, -- n
publicExponent INTEGER -- e }
So that says that the first INTEGER we read is the Modulus value, and the second is (public)Exponent.
The DER encoding is big-endian, which is also the RSAParameters encoding, but for RSAParameters you need to remove leading 0x00 values from Modulus.
While that isn't as easy as giving you the code to do it, it should be fairly straightforward to write a parser for RSA keys given this information. I'd recommend that you write it as internal static RSAParameters ReadRsaPublicKey(...), and then you just need to do
RSAParameters rsaParameters = ReadRsaPublicKey(...);
using (RSA rsa = RSA.Create())
{
rsa.ImportParameters(rsaParameters);
// things you want to do with the key go here
}

After a lot of time, searching and bartonjs's outstanding response, the code to do this is actually straight forward in the end albeit a little unintuitive to anyone not familiar with the structure of a public key.
TL;DR Basically, if your public key is coming from a non-.NET source, this answer won't help as .NET doesn't provide a way to natively parse a correctly formed PEM. However, if the code that generated the PEM is .NET based, then this answer describes the creation of the public key-only PEM and how to load it back in.
A public key PEM can describe a variety of key types, not just RSA so rather than something like new RSACryptoServiceProvider(pemBytes), we have to parse the PEM based on its structure/syntax, ASN.1, and it then tells us if it's an RSA key (it could be a range of others). Knowing that;
const string rsaOid = "1.2.840.113549.1.1.1"; // found under System.Security.Cryptography.CngLightup.RsaOid but it's marked as private
Oid oid = new Oid(rsaOid);
AsnEncodedData keyValue = new AsnEncodedData(publicKeyBytes); // see question
AsnEncodedData keyParam = new AsnEncodedData(new byte[] { 05, 00 }); // ASN.1 code for NULL
PublicKey pubKeyRdr = new PublicKey(oid, keyParam, keyValue);
var rsaCryptoServiceProvider = (RSACryptoServiceProvider)pubKeyRdr.Key;
NOTE: The above code is not production ready! You'll need to put appropriate guards around the object creation (e.g. the public key might not be RSA), the cast to RSACryptoServiceProvider, etc. The code sample here is short to illustrate that it can be done reasonably cleanly.
How did I get this? Spelunking down through the Cryptographic namespace in ILSpy, I had noticed AsnEncodedData which rang a bell with bartonjs's description. Doing more research, I happened upon this post (look familiar?). This was trying to determine the key size specifically but it creates the necessary RSACryptoServiceProvider along the way.
I'm leaving bartonjs's answer as Accepted, and rightly so. The code above is the result of that research and I'm leaving it here so that others looking to do the same can do so cleanly without any array copying hacks like I had in my OP.
Also, for decoding and testing purposes, you can check if your public key is parsable using the ASN.1 decoder here.
UPDATE
It's on the .NET roadmap to make this easier with ASN.1 parsing for Core >2.1.0.
UPDATE 2
There is now a private implementation in Core .NET 2.1.1. MS is dogfooding until satisfied all is well and we'll (hopefully) see the public API in a subsequent version.
UPDATE 3
As I found out via a question here, the above info is incomplete. What's missing is that the public key being loaded with this solution is one that was generated programmatically from a loaded public+private key pair. Once an RSACryptoServiceProvider is created from a key pair (not just the public key), you can export just the public bytes and encode them as a public key PEM. Doing so will be compatible with the solution here. What's with this?
Load the public + private keypair into an RSACryptoServiceProvider and then export it like so;
var cert = new X509Certificate2(keypairBytes, password,
X509KeyStorageFlags.Exportable
| X509KeyStorageFlags.MachineKeySet);
var partialAsnBlockWithPublicKey = cert.GetPublicKey();
// export bytes to PEM format
var base64Encoded = Convert.ToBase64String(partialAsnBlockWithPublicKey, Base64FormattingOptions.InsertLineBreaks);
var pemHeader = "-----BEGIN PUBLIC KEY-----";
var pemFooter = "-----END PUBLIC KEY-----";
var pemFull = string.Format("{0}\r\n{1}\r\n{2}", pemHeader, base64Encoded, pemFooter);
If you create a PEM from this key, you'll be able to load it back in using the method described earlier. Why is this different? The call to cert.GetPublicKey() will actually return the ASN.1 block structure;
SEQUENCE(2 elem)
INTEGER (2048 bit)
INTEGER 65537
This is actually an incomplete DER blob but one which .NET can decode (full ASN.1 parsing and generation is not supported by .NET at time of writing - https://github.com/dotnet/designs/issues/11).
A correct DER (ASN.1) encoded public key bytes has the following structure;
SEQUENCE(2 elem)
SEQUENCE(2 elem)
OBJECT IDENTIFIER "1.2.840.113549.1.1.1" - rsaEncryption(PKCS #1)
NULL
BIT STRING(1 elem)
SEQUENCE(2 elem)
INTEGER (2048 bit)
INTEGER 65537
OK, so the above gets you a public key (kind of) that you can load. It's ugly and technically incomplete but does use .NET's own output from RSACryptoServiceProvider.GetPublicCert() method. The constructor can use those same bytes when loading just the public key later. Unfortunately, it's not a true, fully-formed PEM. We're still awaiting MS's ASN.1 parser in .NET Core 3.0>.

PEM files are just a serie of base64 encoded DER files and .net allow to import directly DER files, so you can do something like this (I assume you're using just the public key as you state you use it only):
byte[] certBytes = Convert.FromBase64String(deserializedPublicKey
.Replace("-----BEGIN PUBLIC KEY-----", "")
.Replace("-----END PUBLIC KEY-----", ""));
X509Certificate2 cert = new X509Certificate2(certBytes);
RSACryptoServiceProvider publicKeyProvider =
(RSACryptoServiceProvider)cert.PublicKey.Key;

Excel CSV Encoding issues

I have a question about danish characters and open saved file as CSV in Excel. See the code below:
[HttpGet]
[Route("/progress/data.csv")]
[Produces("text/csv")]
public IActionResult GetCSV()
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("æø;2;3;");
Encoding encode = Encoding.UTF8;
return File(encode.GetBytes(sb.ToString()), "text/csv", "data.csv");
}
I am using .NET Core 2.1 and the result of this export is that the two first characters æø are displayed as æà .
I am aware that this is a known problem but I have so far not found a solution for it. During the last 4 hours I have tried at least 15 different ways, including UTF with/without BOM. Manually adding BOM with System.Text.Encoding.UTF8.GetPreamble(), various MemoryStream, StreamWriter solutions, tried using windows-1252 with CodePagesEncodingProvider.Instance.GetEncoding(1252) but nothing works. When open this file up in Excel the result is always soemthing different than expected.
Anyone that has a solution for this?

Well ,the problem is the way of Excel to deal with BOM . You might found out to use a StreamWriter :
StreamWriter defaults to using an instance of UTF8Encoding unless specified otherwise. This instance of UTF8Encoding is constructed without a byte order mark (BOM), so its GetPreamble method returns an empty byte array. The default UTF-8 encoding for this constructor throws an exception on invalid bytes. This behavior is different from the behavior provided by the encoding object in the Encoding.UTF8 property. To specify a BOM and determine whether an exception is thrown on invalid bytes, use a constructor that accepts an encoding object as a parameter, such as StreamWriter(String, Boolean, Encoding) or StreamWriter.
So I just create a custom implementation of IActionResult :
public class Utf8ForExcelCsvResult : IActionResult
{
public string Content{get;set;}
public string ContentType{get;set;}
public string FileName {get;set;}
public Task ExecuteResultAsync(ActionContext context)
{
var Response =context.HttpContext.Response;
Response.Headers["Content-Type"] = this.ContentType;
Response.Headers["Content-Disposition"]=$"attachment; filename={this.FileName}; filename*=UTF-8''{this.FileName}";
using(var sw = new StreamWriter(Response.Body,System.Text.Encoding.UTF8)){
sw.Write(Content);
}
return Task.CompletedTask ;
}
}
When you need open such a csv file using Excel , simply return a Utf8ForExcelCsvResult .
[HttpGet]
[Route("/progress/data.csv")]
[Produces("text/csv")]
public IActionResult MyFileDownload()
// public Utf8ForExcelCsvResult MyFileDownload()
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("æø;2;3;");
sb.AppendLine("გამარჯობა");
sb.AppendLine("ဟယ်လို");
sb.AppendLine("ສະບາຍດີ");
sb.AppendLine("cześć");
sb.AppendLine("こんにちは");
sb.AppendLine("你好");
Console.WriteLine(sb.ToString());
return new Utf8ForExcelCsvResult(){
Content=sb.ToString(),
ContentType="text/csv",
FileName="hello.csv",
};
}
We can use Powershell to inspect the HEX representation of csv file by Format-hex -path .\hello.csv :
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
00000000 EF BB BF C3 A6 C3 B8 3B 32 3B 33 3B 0D 0A E1 83 æø;2;3;..á
00000010 92 E1 83 90 E1 83 9B E1 83 90 E1 83 A0 E1 83 AF ááá á¯
00000020 E1 83 9D E1 83 91 E1 83 90 0D 0A E1 80 9F E1 80 ááá..áá
00000030 9A E1 80 BA E1 80 9C E1 80 AD E1 80 AF 0D 0A E0 áºáá­á¯..à
00000040 BA AA E0 BA B0 E0 BA 9A E0 BA B2 E0 BA 8D E0 BA ºªàº°àºàº²àºàº
00000050 94 E0 BA B5 0D 0A 63 7A 65 C5 9B C4 87 0D 0A E3 ີ..czeÅ..ã
00000060 81 93 E3 82 93 E3 81 AB E3 81 A1 E3 81 AF 0D 0A ãã«ã¡ã¯..
00000070 E4 BD A0 E5 A5 BD 0D 0A 你好..
Here the first three bytes EF BB BF are the Byte order marks

phpseclib rsa decryption return false

I'm trying to implement public-private key encryption/decryption for c# server and website. If I encrypt with the public key on PHP I can easily decrypt it using the private key, but when I encrypt the data in C# with the public key I cannot decrypt it with the private key on PHP. Basically, return nothing (or false from var_dump).
C#
var pkey = $"<RSAKeyValue>\r\n\t<Modulus>MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCsaxzQmdhvuM+yjJJgpVHUr0DW 3XbAr/sWbSdceanVX7IhccU8XCGurrM7rNYWhyIBzD8/RGGnqupfdt3rsNYvMKMO rU6thBEDBUVYJO58olDgW7ACbd/u95/0uRPzwGeqDQUn565iDfMyU6+jjaoGn7+D 5D0Bt8x6mLiu43y0zQIDAQAB</Modulus>\r\n\t<Exponent>AQAB</Exponent>\r\n</RSAKeyValue>";
//Encrypting the text using the public key
cipher = new RSACryptoServiceProvider();
cipher.FromXmlString(pkey);
byte[] data = Encoding.UTF8.GetBytes(message);
byte[] cipherText = cipher.Encrypt(data, false);
var encrypted = Convert.ToBase64String(cipherText);
Console.WriteLine(encrypted);
C# code image
From PHP
$rsa = new RSA();
$rsa->loadKey('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');
$convert = base64_decode("CkR7GLQZFUHLcFnhMGxsLYX/4rbrOM+NaXFLyTED3H+xbTChLsXRBQTGo7Xme44b4+/1c7SWahah/FI4gqFx5aDJ1olUmvUR/cto2X7QjBbIBJiFmXRAokbyyBBZ14v8iFqHwunv6Yc+5k/kO/fMK41mJn8xQms+K79CERkCASB7W3dxAFqh06Ksq/Mi9HwW0RakIsbHsdhu3hGQQy4d4h5J");
var_dump($rsa->decrypt($convert));
Note: Those keys are not real and they are generated for development purpose
Link to testing environment code

Wrong padding scheme
You have to use the exact same padding scheme for this to work.
The false in cipher.Encrypt(data, false) disables OAEP. So, PKCS#1 v1.5 padding will be used for encryption.
You have to set the following to use the same padding scheme:
$rsa->setEncryptionMode(RSA::ENCRYPTION_PKCS1);
Broken keys
Keep in mind that you need to use proper keys for that. You seem to be using keys from here for testing purposes.
If we decode the public key, we get this in Hex:
modulus = 94 FB 56 CB 7C F9 9C 63 BA AB 17 F7 53 6C 0B 6E 26 5B F8 47 F1 55 73 55 84 1F D1 CA 53 48 D0 8D 7F E7 FD D6 FD BF 3F F1 D2 2D ED 7B F6 CA 2C D1 1C C1 48 41 BB E3 D6 3E 73 AD FE A5 54 44 6F 41 51 3E 91 B0 24 45 52 7D 02 C8 68 94 2A 8C B8 E6 8F 4A FE 62 40 1E 66 EB 36 DA D4 07 A7 24 AD 82 C5 EF 96 39 D2 75 0D B0 15 47 50 3C 3C C9 0C A6 9A 23 81 4F 58 1C FC A3 39 B3 5C 53 CF 8E 0B 33
exponent = 01 00 01
We can use this tool to convert this Hex representation to a Base64 representation. Remember, do not transmit your private key if you want to transform it. Your public key for C# would look like this:
<RSAKeyValue><Modulus>lPtWy3z5nGO6qxf3U2wLbiZb+EfxVXNVhB/RylNI0I1/5/3W/b8/8dIt7Xv2yizRHMFIQbvj1j5zrf6lVERvQVE+kbAkRVJ9AsholCqMuOaPSv5iQB5m6zba1AenJK2Cxe+WOdJ1DbAVR1A8PMkMppojgU9YHPyjObNcU8+OCzM=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>
Now to your private key. PHP supports multiline strings. Use them! You tried to reduce your private key to a single line and because of that, you made a mistake. Newline characters are \n not /n.
Solution
C# example:
var pkey = "<RSAKeyValue><Modulus>lPtWy3z5nGO6qxf3U2wLbiZb+EfxVXNVhB/RylNI0I1/5/3W/b8/8dIt7Xv2yizRHMFIQbvj1j5zrf6lVERvQVE+kbAkRVJ9AsholCqMuOaPSv5iQB5m6zba1AenJK2Cxe+WOdJ1DbAVR1A8PMkMppojgU9YHPyjObNcU8+OCzM=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";
var cipher = new RSACryptoServiceProvider();
cipher.FromXmlString(pkey);
byte[] data = Encoding.UTF8.GetBytes("some message");
byte[] cipherText = cipher.Encrypt(data, false);
var encrypted = Convert.ToBase64String(cipherText);
Console.WriteLine(encrypted);
C# output:
kRyQsT55mQWmjQ0n1GbXOpaoMvng/BDNWk/0S2G4cqsKD1Fm7ktFdQIvnGlY6kbPXY0unwzGHbBpUGrALOITeyPHCRdsGIGVUc2O0lqI74QROloyoShXwX7TyAwzLJB6yiVSM7SDpy/6wJ5XkHLZRJu9KxmFrIBgOB9+b2x6C4A=
PHP example:
use \phpseclib\Crypt\RSA;
$private_key = "-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----";
$rsa = new RSA();
var_dump($rsa->loadKey($private_key));
$rsa->setEncryptionMode(RSA::ENCRYPTION_PKCS1);
$convert = base64_decode("kRyQsT55mQWmjQ0n1GbXOpaoMvng/BDNWk/0S2G4cqsKD1Fm7ktFdQIvnGlY6kbPXY0unwzGHbBpUGrALOITeyPHCRdsGIGVUc2O0lqI74QROloyoShXwX7TyAwzLJB6yiVSM7SDpy/6wJ5XkHLZRJu9KxmFrIBgOB9+b2x6C4A=");
var_dump($rsa->decrypt($convert));
PHP output:
bool(true)
string(12) "some message"

Read in a DER formatted private key using System.Security.Cryptography [duplicate]

I am using openssl 0.9.6g and I have created public/private keypair using RSA_generate_key(). When I save the key with PEM_write_bio_RSAPublicKey, it gives me keys like:
-----BEGIN RSA PUBLIC KEY-----
...
-----END RSA PUBLIC KEY-----
I have another module in .NET which throws an exception when passed in this key due to its format. It takes format like:
-----BEGIN PUBLIC KEY-----
...
-----END PUBLIC KEY-----
How to convert my keys to this format. I am using C++.
In .NET, I am using openssl.net, the code is as follows:
string publicKey = #"-----BEGIN RSA PUBLIC KEY-----
MIGJAoGBAKGtqUVBBqcGCRYa7Sb6JVQirOX3hggWP2k7CzEtbF/soOONK510Kefm
omXBrGn2t79ES+hAcCvGSiiVZGuEb3UPiznzbiY150SME5nRC+zU0vvdX64ni0Mu
DeUlGcxM1eWSpozO71at6mxLloEMUg0oSWHfAlS5a4LVaURrJqXfAgMBAAE=
-----END RSA PUBLIC KEY-----";
Encoding enc = Encoding.ASCII;
string text = "hello world";
byte[] msg = enc.GetBytes(text);
CryptoKey key = CryptoKey.FromPublicKey(publicKey, "");
RSA rsa = key.GetRSA();
byte[] res = rsa.PublicEncrypt(msg, RSA.Padding.PKCS1);
The exception comes in line:
CryptoKey key = CryptoKey.FromPublicKey(publicKey, "");
If I use the key:
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCbhcU+fhYmYLESZQAj1hKBXsNY
si0kYHNkxpP7ftxZiTFowWUVXHzQgkcYiCNnp3pt1eG6Vt0WDzyFYXqUUqugvX41
gkaIrKQw/sRiWEx49krcz7Vxr3dufL6Mg3eK7NyWDGsqwFrx/qVNqdhsHg12PGNx
IMY4UBtxin2A8pd4OwIDAQAB
-----END PUBLIC KEY-----
It works fine.
I was looking around for this issue. I think what I am looking for is "how to convert rsa public key from pkcs#1 to x509 format.

I am using openssl 0.9.6g and I have created public/private keypair
using RSA_generate_key(). It gives me keys like:
-----BEGIN RSA PUBLIC KEY-----
...
-----END RSA PUBLIC KEY-----
I think what I am looking for is "how to convert rsa public key from pkcs#1 to x509 format.
Yeah, .Net can consume some ASN.1/DER encoded keys, and some PEM encoded keys. The difference is PKCS encoding versus Traditional encoding (OpenSSL calls it "Traditional"). The traditional encoding is the SubjectPublicKeyInfo and it includes the OID and the public key.
So you are looking for either an ASN.1/DER encoding or a PEM encoding that writes SubjectPublicKeyInfo, and not just the public key.
I have another module in .NET which throws an exception when passed in
this key due to its format. It takes format like:
-----BEGIN PUBLIC KEY-----
...
-----END PUBLIC KEY-----
In this case, use PEM_write_bio_PUBKEY rather than PEM_write_bio_RSAPublicKey.
PEM_write_bio_PUBKEY writes the SubjectPublicKeyInfo; while PEM_write_bio_RSAPublicKey writes only the public key.
You will need an EVP_PKEY, so use EVP_PKEY_set1_RSA to convert it.
This is a PKCS key in OpenSSL. Its just the public key. You would use PEM_write_RSAPublicKey to write it:
-----BEGIN RSA PUBLIC KEY-----
And this is a Traditional key in OpenSSL. Its the SubjectPublicKeyInfo, and it includes an OID for the algorithm (rsaEncryption) and the public key. You would use PEM_write_bio_PUBKEY to write it:
-----BEGIN PUBLIC KEY-----
Instead of saving the key with PEM_write_RSAPublicKey, you should write out the SubjectPublicKeyInfo structure in ASN.1/DER format with i2d_RSA_PUBKEY_bio; or write it out in PEM format with PEM_write_bio_PUBKEY.
The program below creates a RSA key pair, and then writes out the public key in all the formats. Be sure to save the private key, too.
(And I'm glad you have the C++ tag. unique_ptr makes this exercise so much easier).
#include <memory>
using std::unique_ptr;
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/bio.h>
#include <openssl/x509.h>
#include <cassert>
#define ASSERT assert
using BN_ptr = std::unique_ptr<BIGNUM, decltype(&::BN_free)>;
using RSA_ptr = std::unique_ptr<RSA, decltype(&::RSA_free)>;
using EVP_KEY_ptr = std::unique_ptr<EVP_PKEY, decltype(&::EVP_PKEY_free)>;
using BIO_FILE_ptr = std::unique_ptr<BIO, decltype(&::BIO_free)>;
int main(int argc, char* argv[])
{
int rc;
RSA_ptr rsa(RSA_new(), ::RSA_free);
BN_ptr bn(BN_new(), ::BN_free);
BIO_FILE_ptr pem1(BIO_new_file("rsa-public-1.pem", "w"), ::BIO_free);
BIO_FILE_ptr pem2(BIO_new_file("rsa-public-2.pem", "w"), ::BIO_free);
BIO_FILE_ptr der1(BIO_new_file("rsa-public-1.der", "w"), ::BIO_free);
BIO_FILE_ptr der2(BIO_new_file("rsa-public-2.der", "w"), ::BIO_free);
rc = BN_set_word(bn.get(), RSA_F4);
ASSERT(rc == 1);
// Generate key
rc = RSA_generate_key_ex(rsa.get(), 2048, bn.get(), NULL);
ASSERT(rc == 1);
// Convert RSA key to PKEY
EVP_KEY_ptr pkey(EVP_PKEY_new(), ::EVP_PKEY_free);
rc = EVP_PKEY_set1_RSA(pkey.get(), rsa.get());
ASSERT(rc == 1);
//////////
// Write just the public key in ASN.1/DER
// Load with d2i_RSAPublicKey_bio
rc = i2d_RSAPublicKey_bio(der1.get(), rsa.get());
ASSERT(rc == 1);
// Write just the public key in PEM
// Load with PEM_read_bio_RSAPublicKey
rc = PEM_write_bio_RSAPublicKey(pem1.get(), rsa.get());
ASSERT(rc == 1);
// Write SubjectPublicKeyInfo with OID and public key in ASN.1/DER
// Load with d2i_RSA_PUBKEY_bio
rc = i2d_RSA_PUBKEY_bio(der2.get(), rsa.get());
ASSERT(rc == 1);
// Write SubjectPublicKeyInfo with OID and public key in PEM
// Load with PEM_read_bio_PUBKEY
rc = PEM_write_bio_PUBKEY(pem2.get(), pkey.get());
ASSERT(rc == 1);
return 0;
}
The set1 in EVP_PKEY_set1_RSA bumps the reference count, so you don't get a segfault on a double free.
After executing the program, you get the expected PEM and ASN.1/DER:
$ cat rsa-public-1.pem
-----BEGIN RSA PUBLIC KEY-----
MIIBCgKCAQEA0cgFv6wEcqoOhPtHdVmX4YFlCwodnSqooeCxFF1XadTS4sZkVJTC
kszHmRqXiXL2NmqnuDQsq6nLd+sNoU5yJJ+W1hwo7UToCyJ/81tS4n6mXvF8oilP
8YudD5QnBdW9LhqttBIN4Gk+Cxun+HG1rSJLGP9yiPPFd7DPiFz0Gd+juyWznWnP
gapDIWEKqANKma3j6b9eopBDWB0XAgU0HQ71MSNbcsPvDd23Ftx0re/7jG53V7Bn
eBy7fQsPmxcn4c74Lz4CvhOr7VdQpeBzNeG2CtkefKWyTk7Vu4FZnAgNd/202XAr
c6GmEQqD2M2zXH/nVZg5oLznECDVQ1x/pwIDAQAB
-----END RSA PUBLIC KEY-----
$ cat rsa-public-2.pem
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0cgFv6wEcqoOhPtHdVmX
4YFlCwodnSqooeCxFF1XadTS4sZkVJTCkszHmRqXiXL2NmqnuDQsq6nLd+sNoU5y
JJ+W1hwo7UToCyJ/81tS4n6mXvF8oilP8YudD5QnBdW9LhqttBIN4Gk+Cxun+HG1
rSJLGP9yiPPFd7DPiFz0Gd+juyWznWnPgapDIWEKqANKma3j6b9eopBDWB0XAgU0
HQ71MSNbcsPvDd23Ftx0re/7jG53V7BneBy7fQsPmxcn4c74Lz4CvhOr7VdQpeBz
NeG2CtkefKWyTk7Vu4FZnAgNd/202XArc6GmEQqD2M2zXH/nVZg5oLznECDVQ1x/
pwIDAQAB
-----END PUBLIC KEY-----
$ dumpasn1 rsa-public-1.der
0 266: SEQUENCE {
4 257: INTEGER
: 00 D1 C8 05 BF AC 04 72 AA 0E 84 FB 47 75 59 97
: E1 81 65 0B 0A 1D 9D 2A A8 A1 E0 B1 14 5D 57 69
: D4 D2 E2 C6 64 54 94 C2 92 CC C7 99 1A 97 89 72
: F6 36 6A A7 B8 34 2C AB A9 CB 77 EB 0D A1 4E 72
: 24 9F 96 D6 1C 28 ED 44 E8 0B 22 7F F3 5B 52 E2
: 7E A6 5E F1 7C A2 29 4F F1 8B 9D 0F 94 27 05 D5
: BD 2E 1A AD B4 12 0D E0 69 3E 0B 1B A7 F8 71 B5
: AD 22 4B 18 FF 72 88 F3 C5 77 B0 CF 88 5C F4 19
: [ Another 129 bytes skipped ]
265 3: INTEGER 65537
: }
0 warnings, 0 errors.
$ dumpasn1 rsa-public-2.der
0 290: SEQUENCE {
4 13: SEQUENCE {
6 9: OBJECT IDENTIFIER rsaEncryption (1 2 840 113549 1 1 1)
17 0: NULL
: }
19 271: BIT STRING, encapsulates {
24 266: SEQUENCE {
28 257: INTEGER
: 00 D1 C8 05 BF AC 04 72 AA 0E 84 FB 47 75 59 97
: E1 81 65 0B 0A 1D 9D 2A A8 A1 E0 B1 14 5D 57 69
: D4 D2 E2 C6 64 54 94 C2 92 CC C7 99 1A 97 89 72
: F6 36 6A A7 B8 34 2C AB A9 CB 77 EB 0D A1 4E 72
: 24 9F 96 D6 1C 28 ED 44 E8 0B 22 7F F3 5B 52 E2
: 7E A6 5E F1 7C A2 29 4F F1 8B 9D 0F 94 27 05 D5
: BD 2E 1A AD B4 12 0D E0 69 3E 0B 1B A7 F8 71 B5
: AD 22 4B 18 FF 72 88 F3 C5 77 B0 CF 88 5C F4 19
: [ Another 129 bytes skipped ]
289 3: INTEGER 65537
: }
: }
: }
0 warnings, 0 errors.
Related, see How to generate RSA private key using openssl?. It shows you how to write a RSA public and private key in a number of formats.

C# : Japanese characters with unicode encoding

The intention of the code is printing unicode as japanese characters to a file
String s = "\u30a2\u30c3\u30d7\u30ed\u30fc\u30c9\u3059\u308b\u30d5\u30a1\u30a4\u30eb\u304c\u6307\u5b9a\u3055\u308c\u3066\u3044\u307e\u305b\u3093";
var Bytes = Encoding.Unicode.GetBytes(s);
string key = Encoding.UTF8.GetString(Encoding.Convert(Encoding.Unicode, Encoding.UTF8, Bytes));
Key is I want to print to file but has the value \u30a2\u30c3\u30d7\u30ed\u30fc\u30c9\u3059\u308b\u30d5\u30a1\u30a4\u30eb\u304c\u6307\u5b9a\u3055\u308c\u3066\u3044\u307e\u305b\u3093 Any ideas whats wrong?

What's wrong is that a string (key) has no notion of the bytes used to store it. In this case, your string is:
String:
アップロードするファイルが指定されていません
this is exactly what
"\u30a2\u30c3\u30d7\u30ed\u30fc\u30c9\u3059\u308b\u30d5\u30a1\u30a4\u30eb\u304c\u6307\u5b9a\u3055\u308c\u3066\u3044\u307e\u305b\u3093"
means. The expression '\u30a3' looks like 2 Unicode bytes, but it actually just means the character 'ア'.
if you save to a UTF-8 file, the bytes written will be:
UTF-8 bytes
File.WriteAllText("temp.txt", "アップロードするファイルが指定されていません", Encoding.UTF8);
The contents will be (in bytes)
E3 82 A2 E3 83 83 E3 83 97 E3 83 AD E3 83 BC E3 83 89 E3 81 99 E3 82 8B E3 83
95 E3 82 A1 E3 82 A4 E3 83 AB E3 81 8C E6 8C 87 E5 AE 9A E3 81 95 E3 82 8C E3
81 A6 E3 81 84 E3 81 BE E3 81 9B E3 82 93
UTF-16 bytes
File.WriteAllText("temp.txt", "アップロードするファイルが指定されていません", Encoding.Unicode);
The contents will be (in bytes)
A2 30 C3 30 D7 30 ED 30 FC 30 C9 30 59 30 8B 30 D5 30 A1 30 A4 30 EB 30 4C 30
07 63 9A 5B 55 30 8C 30 66 30 44 30 7E 30 5B 30 93 30

One doesn't "convert" Unicode to UTF-8 :-/
Unicode, besides being the parent for the entire set of specifications, can be thought of as "simply" defining code-points/characters and the rules of interaction. The UTF-8 encoding is the specific set of rules to map a sequence of Unicode code-points into a sequence of octets (8-bit bytes).
Try this in LINQPad:
String s = "\u30a2\u30c3\u30d7\u30ed";
s.Dump(); // original string
var bytes = Encoding.UTF8.GetBytes(s);
bytes.Dump(); // see UTF-8 encoded byte sequence
string key = Encoding.UTF8.GetString(bytes);
key.Dump(); // contents restored
The UTF-8 exists only in bytes.
Happy coding.