C＃でファイルからRSA公開鍵をロードする方法
RSACryptoServiceProviderクラスで使用するファイルから次のRSA公開キーを読み込む必要があります。これどうやってするの？
-----BEGIN PUBLIC KEY-----
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/syEKqEkMtQL0+d
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX+izR
KbGMRtur2TYklnyVkjeeHfAggo8vWQmWesnOG55vQYHbOOFoJbk0EkwEr5R/PbKm
byXPPN8zwnS5/XXXXXXXXXXXX
-----END PUBLIC KEY-----
このコードは私のpubキーで動作します： http://www.jensign.com/opensslkey/
ここに私が使用しているコードがあります
static string RSA(string input)
{
RSACryptoServiceProvider rsa = DecodeX509PublicKey(Convert.FromBase64String(GetKey()));
return (Convert.ToBase64String(rsa.Encrypt(Encoding.ASCII.GetBytes(input), false)));
}
static string GetKey()
{
return File.ReadAllText("master.pub").Replace("-----BEGIN PUBLIC KEY-----", "").Replace("-----END PUBLIC KEY-----", "");
//.Replace("\n", "");
}
private static bool CompareBytearrays(byte[] a, byte[] b)
{
if (a.Length != b.Length)
return false;
int i = 0;
foreach (byte c in a)
{
if (c != b[i])
return false;
i++;
}
return true;
}
public static RSACryptoServiceProvider DecodeX509PublicKey(byte[] x509key)
{
// encoded OID sequence for PKCS #1 rsaEncryption szOID_RSA_RSA = "1.2.840.113549.1.1.1"
byte[] SeqOID = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
byte[] seq = new byte[15];
// --------- Set up stream to read the asn.1 encoded SubjectPublicKeyInfo blob ------
MemoryStream mem = new MemoryStream(x509key);
BinaryReader binr = new BinaryReader(mem); //wrap Memory Stream with BinaryReader for easy reading
byte bt = 0;
ushort twobytes = 0;
try
{
twobytes = binr.ReadUInt16();
if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
binr.ReadByte(); //advance 1 byte
else if (twobytes == 0x8230)
binr.ReadInt16(); //advance 2 bytes
else
return null;
seq = binr.ReadBytes(15); //read the Sequence OID
if (!CompareBytearrays(seq, SeqOID)) //make sure Sequence for OID is correct
return null;
twobytes = binr.ReadUInt16();
if (twobytes == 0x8103) //data read as little endian order (actual data order for Bit String is 03 81)
binr.ReadByte(); //advance 1 byte
else if (twobytes == 0x8203)
binr.ReadInt16(); //advance 2 bytes
else
return null;
bt = binr.ReadByte();
if (bt != 0x00) //expect null byte next
return null;
twobytes = binr.ReadUInt16();
if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
binr.ReadByte(); //advance 1 byte
else if (twobytes == 0x8230)
binr.ReadInt16(); //advance 2 bytes
else
return null;
twobytes = binr.ReadUInt16();
byte lowbyte = 0x00;
byte highbyte = 0x00;
if (twobytes == 0x8102) //data read as little endian order (actual data order for Integer is 02 81)
lowbyte = binr.ReadByte(); // read next bytes which is bytes in modulus
else if (twobytes == 0x8202)
{
highbyte = binr.ReadByte(); //advance 2 bytes
lowbyte = binr.ReadByte();
}
else
return null;
byte[] modint = { lowbyte, highbyte, 0x00, 0x00 }; //reverse byte order since asn.1 key uses big endian order
int modsize = BitConverter.ToInt32(modint, 0);
byte firstbyte = binr.ReadByte();
binr.BaseStream.Seek(-1, SeekOrigin.Current);
if (firstbyte == 0x00)
{ //if first byte (highest order) of modulus is zero, don't include it
binr.ReadByte(); //skip this null byte
modsize -= 1; //reduce modulus buffer size by 1
}
byte[] modulus = binr.ReadBytes(modsize); //read the modulus bytes
if (binr.ReadByte() != 0x02) //expect an Integer for the exponent data
return null;
int expbytes = (int)binr.ReadByte(); // should only need one byte for actual exponent data (for all useful values)
byte[] exponent = binr.ReadBytes(expbytes);
// ------- create RSACryptoServiceProvider instance and initialize with public key -----
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSAParameters RSAKeyInfo = new RSAParameters();
RSAKeyInfo.Modulus = modulus;
RSAKeyInfo.Exponent = exponent;
RSA.ImportParameters(RSAKeyInfo);
return RSA;
}
catch (Exception)
{
return null;
}
finally { binr.Close(); }
}
暗号化するテキストを指定して「RSA」メソッドを呼び出すだけで完了です。
次のクラス（RSACryptoServiceProviderメソッド）を使用して、PEMファイルからGetRSAProviderFromPemFileを作成できます。
警告：検証せずにStackOverflowからコードをコピーしないでください！特に暗号コードではありません！このコードにはバグがあります（コメントを参照）。本番環境でこれを使用する前に、テストを作成して実行することをお勧めします（本当に良いオプションがない場合）。テストとアクティブなメンテナーなしで。
出典：このコードは、 このサイト のopensslkeyから取ったようです。 Copyright（c）2000 JavaScience Consulting、Michel Gallant。元のパッケージはBSDライクなライセンスの下でリリースされたため、おそらく使用しても問題ありません（ただし、再確認することをお勧めします）。同じ著者による NuGetパッケージ もあります。
この回答に最初に投稿されたコピーペーストされたソースコードは次のとおりです。
RSACryptoServiceProvider provider = PemKeyUtils.GetRSAProviderFromPemFile( @"public_key.pem" );
public class PemKeyUtils
{
const String pemprivheader = "-----BEGIN RSA PRIVATE KEY-----";
const String pemprivfooter = "-----END RSA PRIVATE KEY-----";
const String pempubheader = "-----BEGIN PUBLIC KEY-----";
const String pempubfooter = "-----END PUBLIC KEY-----";
const String pemp8header = "-----BEGIN PRIVATE KEY-----";
const String pemp8footer = "-----END PRIVATE KEY-----";
const String pemp8encheader = "-----BEGIN ENCRYPTED PRIVATE KEY-----";
const String pemp8encfooter = "-----END ENCRYPTED PRIVATE KEY-----";
static bool verbose = false;
public static RSACryptoServiceProvider GetRSAProviderFromPemFile( String pemfile )
{
bool isPrivateKeyFile = true;
string pemstr = File.ReadAllText( pemfile ).Trim();
if (pemstr.StartsWith( pempubheader ) && pemstr.EndsWith( pempubfooter ))
isPrivateKeyFile = false;
byte[] pemkey;
if (isPrivateKeyFile)
pemkey = DecodeOpenSSLPrivateKey( pemstr );
else
pemkey = DecodeOpenSSLPublicKey( pemstr );
if (pemkey == null)
return null;
if (isPrivateKeyFile)
return DecodeRSAPrivateKey( pemkey );
else
return DecodeX509PublicKey( pemkey );
}
//-------- Get the binary RSA PUBLIC key --------
static byte[] DecodeOpenSSLPublicKey( String instr )
{
const String pempubheader = "-----BEGIN PUBLIC KEY-----";
const String pempubfooter = "-----END PUBLIC KEY-----";
String pemstr = instr.Trim();
byte[] binkey;
if (!pemstr.StartsWith( pempubheader ) || !pemstr.EndsWith( pempubfooter ))
return null;
StringBuilder sb = new StringBuilder( pemstr );
sb.Replace( pempubheader, "" ); //remove headers/footers, if present
sb.Replace( pempubfooter, "" );
String pubstr = sb.ToString().Trim(); //get string after removing leading/trailing whitespace
try
{
binkey = Convert.FromBase64String( pubstr );
}
catch (System.FormatException)
{ //if can't b64 decode, data is not valid
return null;
}
return binkey;
}
static RSACryptoServiceProvider DecodeX509PublicKey(byte[] x509Key)
{
// encoded OID sequence for PKCS #1 rsaEncryption szOID_RSA_RSA = "1.2.840.113549.1.1.1"
byte[] seqOid = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
// --------- Set up stream to read the asn.1 encoded SubjectPublicKeyInfo blob ------
using (var mem = new MemoryStream(x509Key))
{
using (var binr = new BinaryReader(mem)) //wrap Memory Stream with BinaryReader for easy reading
{
try
{
var twobytes = binr.ReadUInt16();
switch (twobytes)
{
case 0x8130:
binr.ReadByte(); //advance 1 byte
break;
case 0x8230:
binr.ReadInt16(); //advance 2 bytes
break;
default:
return null;
}
var seq = binr.ReadBytes(15);
if (!CompareBytearrays(seq, seqOid)) //make sure Sequence for OID is correct
return null;
twobytes = binr.ReadUInt16();
if (twobytes == 0x8103) //data read as little endian order (actual data order for Bit String is 03 81)
binr.ReadByte(); //advance 1 byte
else if (twobytes == 0x8203)
binr.ReadInt16(); //advance 2 bytes
else
return null;
var bt = binr.ReadByte();
if (bt != 0x00) //expect null byte next
return null;
twobytes = binr.ReadUInt16();
if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
binr.ReadByte(); //advance 1 byte
else if (twobytes == 0x8230)
binr.ReadInt16(); //advance 2 bytes
else
return null;
twobytes = binr.ReadUInt16();
byte lowbyte = 0x00;
byte highbyte = 0x00;
if (twobytes == 0x8102) //data read as little endian order (actual data order for Integer is 02 81)
lowbyte = binr.ReadByte(); // read next bytes which is bytes in modulus
else if (twobytes == 0x8202)
{
highbyte = binr.ReadByte(); //advance 2 bytes
lowbyte = binr.ReadByte();
}
else
return null;
byte[] modint = { lowbyte, highbyte, 0x00, 0x00 }; //reverse byte order since asn.1 key uses big endian order
int modsize = BitConverter.ToInt32(modint, 0);
byte firstbyte = binr.ReadByte();
binr.BaseStream.Seek(-1, SeekOrigin.Current);
if (firstbyte == 0x00)
{ //if first byte (highest order) of modulus is zero, don't include it
binr.ReadByte(); //skip this null byte
modsize -= 1; //reduce modulus buffer size by 1
}
byte[] modulus = binr.ReadBytes(modsize); //read the modulus bytes
if (binr.ReadByte() != 0x02) //expect an Integer for the exponent data
return null;
int expbytes = binr.ReadByte(); // should only need one byte for actual exponent data (for all useful values)
byte[] exponent = binr.ReadBytes(expbytes);
// We don't really need to print anything but if we insist to...
//showBytes("\nExponent", exponent);
//showBytes("\nModulus", modulus);
// ------- create RSACryptoServiceProvider instance and initialize with public key -----
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
RSAParameters rsaKeyInfo = new RSAParameters
{
Modulus = modulus,
Exponent = exponent
};
rsa.ImportParameters(rsaKeyInfo);
return rsa;
}
catch (Exception)
{
return null;
}
}
}
}
//------- Parses binary ans.1 RSA private key; returns RSACryptoServiceProvider ---
static RSACryptoServiceProvider DecodeRSAPrivateKey( byte[] privkey )
{
byte[] MODULUS, E, D, P, Q, DP, DQ, IQ;
// --------- Set up stream to decode the asn.1 encoded RSA private key ------
MemoryStream mem = new MemoryStream( privkey );
BinaryReader binr = new BinaryReader( mem ); //wrap Memory Stream with BinaryReader for easy reading
byte bt = 0;
ushort twobytes = 0;
int elems = 0;
try
{
twobytes = binr.ReadUInt16();
if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
binr.ReadByte(); //advance 1 byte
else if (twobytes == 0x8230)
binr.ReadInt16(); //advance 2 bytes
else
return null;
twobytes = binr.ReadUInt16();
if (twobytes != 0x0102) //version number
return null;
bt = binr.ReadByte();
if (bt != 0x00)
return null;
//------ all private key components are Integer sequences ----
elems = GetIntegerSize( binr );
MODULUS = binr.ReadBytes( elems );
elems = GetIntegerSize( binr );
E = binr.ReadBytes( elems );
elems = GetIntegerSize( binr );
D = binr.ReadBytes( elems );
elems = GetIntegerSize( binr );
P = binr.ReadBytes( elems );
elems = GetIntegerSize( binr );
Q = binr.ReadBytes( elems );
elems = GetIntegerSize( binr );
DP = binr.ReadBytes( elems );
elems = GetIntegerSize( binr );
DQ = binr.ReadBytes( elems );
elems = GetIntegerSize( binr );
IQ = binr.ReadBytes( elems );
Console.WriteLine( "showing components .." );
if (verbose)
{
showBytes( "\nModulus", MODULUS );
showBytes( "\nExponent", E );
showBytes( "\nD", D );
showBytes( "\nP", P );
showBytes( "\nQ", Q );
showBytes( "\nDP", DP );
showBytes( "\nDQ", DQ );
showBytes( "\nIQ", IQ );
}
// ------- create RSACryptoServiceProvider instance and initialize with public key -----
RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
RSAParameters RSAparams = new RSAParameters();
RSAparams.Modulus = MODULUS;
RSAparams.Exponent = E;
RSAparams.D = D;
RSAparams.P = P;
RSAparams.Q = Q;
RSAparams.DP = DP;
RSAparams.DQ = DQ;
RSAparams.InverseQ = IQ;
RSA.ImportParameters( RSAparams );
return RSA;
}
catch (Exception)
{
return null;
}
finally { binr.Close(); }
}
private static int GetIntegerSize( BinaryReader binr )
{
byte bt = 0;
byte lowbyte = 0x00;
byte highbyte = 0x00;
int count = 0;
bt = binr.ReadByte();
if (bt != 0x02) //expect integer
return 0;
bt = binr.ReadByte();
if (bt == 0x81)
count = binr.ReadByte(); // data size in next byte
else
if (bt == 0x82)
{
highbyte = binr.ReadByte(); // data size in next 2 bytes
lowbyte = binr.ReadByte();
byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
count = BitConverter.ToInt32( modint, 0 );
}
else
{
count = bt; // we already have the data size
}
while (binr.ReadByte() == 0x00)
{ //remove high order zeros in data
count -= 1;
}
binr.BaseStream.Seek( -1, SeekOrigin.Current ); //last ReadByte wasn't a removed zero, so back up a byte
return count;
}
//----- Get the binary RSA PRIVATE key, decrypting if necessary ----
static byte[] DecodeOpenSSLPrivateKey( String instr )
{
const String pemprivheader = "-----BEGIN RSA PRIVATE KEY-----";
const String pemprivfooter = "-----END RSA PRIVATE KEY-----";
String pemstr = instr.Trim();
byte[] binkey;
if (!pemstr.StartsWith( pemprivheader ) || !pemstr.EndsWith( pemprivfooter ))
return null;
StringBuilder sb = new StringBuilder( pemstr );
sb.Replace( pemprivheader, "" ); //remove headers/footers, if present
sb.Replace( pemprivfooter, "" );
String pvkstr = sb.ToString().Trim(); //get string after removing leading/trailing whitespace
try
{ // if there are no PEM encryption info lines, this is an UNencrypted PEM private key
binkey = Convert.FromBase64String( pvkstr );
return binkey;
}
catch (System.FormatException)
{ //if can't b64 decode, it must be an encrypted private key
//Console.WriteLine("Not an unencrypted OpenSSL PEM private key");
}
StringReader str = new StringReader( pvkstr );
//-------- read PEM encryption info. lines and extract salt -----
if (!str.ReadLine().StartsWith( "Proc-Type: 4,ENCRYPTED" ))
return null;
String saltline = str.ReadLine();
if (!saltline.StartsWith( "DEK-Info: DES-EDE3-CBC," ))
return null;
String saltstr = saltline.Substring( saltline.IndexOf( "," ) + 1 ).Trim();
byte[] salt = new byte[saltstr.Length / 2];
for (int i = 0; i < salt.Length; i++)
salt[i] = Convert.ToByte( saltstr.Substring( i * 2, 2 ), 16 );
if (!(str.ReadLine() == ""))
return null;
//------ remaining b64 data is encrypted RSA key ----
String encryptedstr = str.ReadToEnd();
try
{ //should have b64 encrypted RSA key now
binkey = Convert.FromBase64String( encryptedstr );
}
catch (System.FormatException)
{ // bad b64 data.
return null;
}
//------ Get the 3DES 24 byte key using PDK used by OpenSSL ----
SecureString despswd = GetSecPswd( "Enter password to derive 3DES key==>" );
//Console.Write("\nEnter password to derive 3DES key: ");
//String pswd = Console.ReadLine();
byte[] deskey = GetOpenSSL3deskey( salt, despswd, 1, 2 ); // count=1 (for OpenSSL implementation); 2 iterations to get at least 24 bytes
if (deskey == null)
return null;
//showBytes("3DES key", deskey) ;
//------ Decrypt the encrypted 3des-encrypted RSA private key ------
byte[] rsakey = DecryptKey( binkey, deskey, salt ); //OpenSSL uses salt value in PEM header also as 3DES IV
if (rsakey != null)
return rsakey; //we have a decrypted RSA private key
else
{
Console.WriteLine( "Failed to decrypt RSA private key; probably wrong password." );
return null;
}
}
// ----- Decrypt the 3DES encrypted RSA private key ----------
static byte[] DecryptKey( byte[] cipherData, byte[] desKey, byte[] IV )
{
MemoryStream memst = new MemoryStream();
TripleDES alg = TripleDES.Create();
alg.Key = desKey;
alg.IV = IV;
try
{
CryptoStream cs = new CryptoStream( memst, alg.CreateDecryptor(), CryptoStreamMode.Write );
cs.Write( cipherData, 0, cipherData.Length );
cs.Close();
}
catch (Exception exc)
{
Console.WriteLine( exc.Message );
return null;
}
byte[] decryptedData = memst.ToArray();
return decryptedData;
}
//----- OpenSSL PBKD uses only one hash cycle (count); miter is number of iterations required to build sufficient bytes ---
static byte[] GetOpenSSL3deskey( byte[] salt, SecureString secpswd, int count, int miter )
{
IntPtr unmanagedPswd = IntPtr.Zero;
int HASHLENGTH = 16; //MD5 bytes
byte[] keymaterial = new byte[HASHLENGTH * miter]; //to store contatenated Mi hashed results
byte[] psbytes = new byte[secpswd.Length];
unmanagedPswd = Marshal.SecureStringToGlobalAllocAnsi( secpswd );
Marshal.Copy( unmanagedPswd, psbytes, 0, psbytes.Length );
Marshal.ZeroFreeGlobalAllocAnsi( unmanagedPswd );
//UTF8Encoding utf8 = new UTF8Encoding();
//byte[] psbytes = utf8.GetBytes(pswd);
// --- contatenate salt and pswd bytes into fixed data array ---
byte[] data00 = new byte[psbytes.Length + salt.Length];
Array.Copy( psbytes, data00, psbytes.Length ); //copy the pswd bytes
Array.Copy( salt, 0, data00, psbytes.Length, salt.Length ); //concatenate the salt bytes
// ---- do multi-hashing and contatenate results D1, D2 ... into keymaterial bytes ----
MD5 md5 = new MD5CryptoServiceProvider();
byte[] result = null;
byte[] hashtarget = new byte[HASHLENGTH + data00.Length]; //fixed length initial hashtarget
for (int j = 0; j < miter; j++)
{
// ---- Now hash consecutively for count times ------
if (j == 0)
result = data00; //initialize
else
{
Array.Copy( result, hashtarget, result.Length );
Array.Copy( data00, 0, hashtarget, result.Length, data00.Length );
result = hashtarget;
//Console.WriteLine("Updated new initial hash target:") ;
//showBytes(result) ;
}
for (int i = 0; i < count; i++)
result = md5.ComputeHash( result );
Array.Copy( result, 0, keymaterial, j * HASHLENGTH, result.Length ); //contatenate to keymaterial
}
//showBytes("Final key material", keymaterial);
byte[] deskey = new byte[24];
Array.Copy( keymaterial, deskey, deskey.Length );
Array.Clear( psbytes, 0, psbytes.Length );
Array.Clear( data00, 0, data00.Length );
Array.Clear( result, 0, result.Length );
Array.Clear( hashtarget, 0, hashtarget.Length );
Array.Clear( keymaterial, 0, keymaterial.Length );
return deskey;
}
static SecureString GetSecPswd( String Prompt )
{
SecureString password = new SecureString();
Console.ForegroundColor = ConsoleColor.Gray;
Console.Write( Prompt );
Console.ForegroundColor = ConsoleColor.Magenta;
while (true)
{
ConsoleKeyInfo cki = Console.ReadKey( true );
if (cki.Key == ConsoleKey.Enter)
{
Console.ForegroundColor = ConsoleColor.Gray;
Console.WriteLine();
return password;
}
else if (cki.Key == ConsoleKey.Backspace)
{
// remove the last asterisk from the screen...
if (password.Length > 0)
{
Console.SetCursorPosition( Console.CursorLeft - 1, Console.CursorTop );
Console.Write( " " );
Console.SetCursorPosition( Console.CursorLeft - 1, Console.CursorTop );
password.RemoveAt( password.Length - 1 );
}
}
else if (cki.Key == ConsoleKey.Escape)
{
Console.ForegroundColor = ConsoleColor.Gray;
Console.WriteLine();
return password;
}
else if (Char.IsLetterOrDigit( cki.KeyChar ) || Char.IsSymbol( cki.KeyChar ))
{
if (password.Length < 20)
{
password.AppendChar( cki.KeyChar );
Console.Write( "*" );
}
else
{
Console.Beep();
}
}
else
{
Console.Beep();
}
}
}
static bool CompareBytearrays( byte[] a, byte[] b )
{
if (a.Length != b.Length)
return false;
int i = 0;
foreach (byte c in a)
{
if (c != b[i])
return false;
i++;
}
return true;
}
static void showBytes( String info, byte[] data )
{
Console.WriteLine( "{0} [{1} bytes]", info, data.Length );
for (int i = 1; i <= data.Length; i++)
{
Console.Write( "{0:X2} ", data[i - 1] );
if (i % 16 == 0)
Console.WriteLine();
}
Console.WriteLine( "\n\n" );
}
}
X509証明書について話している場合：
FileStream fs = new FileStream("your_cert_file.crt", FileMode.Open);
byte[] certBytes = new byte[fs.Length];
fs.Read(certBytes, 0, (Int32)fs.Length);
fs.Close();
System.Security.Cryptography.X509Certificates.X509Certificate x509cert =
new X509Certificate(certBytes);
Console.WriteLine(x509cert.GetPublicKey());
Console.WriteLine(x509cert.GetPublicKeyString());
「7/16/2012 15:04:58 Z」で行われた@hkprojのコメントの後に編集されました：
ここを見てみると、「 Bouncy Castleのみを使用してPEM RSA公開鍵を読み取る 」が見つかりました。あなたが望むのはこれだと思います：
using (StreamReader reader = File.OpenText(@"c:\RSA.txt"))
{
Org.BouncyCastle.OpenSsl.PemReader pr =
new Org.BouncyCastle.OpenSsl.PemReader(reader);
Org.BouncyCastle.Utilities.IO.Pem.PemObject po = pr.ReadPemObject();
Console.WriteLine("PemObject, Type: " + po.Type);
Console.WriteLine("PemObject, Length: " + po.Content.Length);
}
ただし、ファイルを使用するとエラーが発生します：System.IO.IOException : base64 data appears to be truncated。
ファイルを次のように変更します。
-----BEGIN PUBLIC KEY-----
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/syEKqEkMtQL0+d
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX+izR
KbGMRtur2TYklnyVkjeeHfAggo8vWQmWesnOG55vQYHbOOFoJbk0EkwEr5R/PbKm
byXPPN8zwnS5/XXXXXXXXXXXXZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
-----END PUBLIC KEY-----
結果は次のとおりです。
PemObject, Type: PUBLIC KEY
PemObject, Length: 192
ファイルに保存されている証明書について話していますか？
次のようなオブジェクトがある場合：
X509Certificate2 certificate;
次のコードを使用できます。
RSACryptoServiceProvider rsaprovider =
(RSACryptoServiceProvider)certificate.PublicKey.Key;
次に、クラスRSACryptoServiceProviderを使用します（ http://msdn.Microsoft.com/en-us/library/system.security.cryptography.rsacryptoserviceprovider.aspx を参照）。
X509Certificate2を読み込むには、そのコンストラクタを使用します（ http://msdn.Microsoft.com/en-us/library/system.security.cryptography.x509certificates.x509certificate2.aspx を参照）。
このプログラムは私のためにうまく機能します：
static void Main(string[] args)
{
try
{
X509Certificate2 certificate =
new X509Certificate2("<PFX Certificate Path", "<Certificate-Password>");
RSACryptoServiceProvider rsaprovider = (RSACryptoServiceProvider)certificate.PublicKey.Key;
}
catch(Exception e)
{
}
}