RSA公钥加密使用的模数和指数

我想使用给定模数和指数值的RSA生成公钥。

public static string RSAPublic(string toEncrypt) {
    var crypt = AsymmetricKeyAlgorithmProvider.OpenAlgorithm(AsymmetricAlgorithmNames.RsaPkcs1);
    var buffer = CryptographicBuffer.ConvertStringToBinary(toEncrypt, BinaryStringEncoding.Utf8);
    string publikKey = modulus + exponent;
    publikKey.Replace("'r'n", "");
    var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(publikKey);
    string pk = System.Convert.ToBase64String(plainTextBytes);
    IBuffer keyBuffer = CryptographicBuffer.DecodeFromBase64String(pk);

    CryptographicKey key = crypt.ImportPublicKey(keyBuffer, CryptographicPublicKeyBlobType.X509SubjectPublicKeyInfo); // Throws exception here, have tried using all the 4 available BlobTypes

    // var key = crypt.CreateKeyPair(512);
    var sigBuffer = CryptographicEngine.Encrypt(key, buffer, null);
    string signature = CryptographicBuffer.EncodeToBase64String(sigBuffer);
    return signature;
}

下面是异常消息:"ASN1 bad tag value met. "(来自HRESULT: 0x8009310B的异常)"

StackTrace: " at windows . security . cryptographic . core . asymmetrickeyalgorithmprovider . "ImportPublicKey(IBuffer keyBlob, CryptographicPublicKeyBlobType BlobType)在MyProject.General.Utility。RSAPublic(字符串toEncrypt)"

我无法找出正确的方法来生成创建加密字符串所需的CryptographicKey。