Decrypt SAML Response with X.509 Certificate and P

Question

I am trying to decrypt a SAML Response with a X.509 Certificate and the Private Key (both stored in local drive) using .NET.

This is the XML file to decrypt:

<samlp:Response xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" Version="2.0" ID="mFCXf3nW6C7tzReKMQjpJ81L9Yu" IssueInstant="2019-09-11T13:29:01.254Z" Destination="https://test.com/sso.aspx" >
  <saml:Issuer xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">saml.test.com</saml:Issuer>
  <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    <ds:SignedInfo>
      <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
      <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256" />
      <ds:Reference URI="#mFCXf3nW6C7tzReKMQjpJ81L9Yu">
        <ds:Transforms>
          <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
          <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
        </ds:Transforms>
        <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256" />
        <ds:DigestValue>ejzCFmHiMyh07qJB88=</ds:DigestValue>
      </ds:Reference>
    </ds:SignedInfo>
    <ds:SignatureValue> FEmLZgeML744VSl 2H5KrPBSBPuHnVtVzo5APGqy/D4YPqgEpW5kOhV3aDpV6ZH/K0FBonrYFaoDn7eG4rIWoDhJAhdh pas9O70JgqIxi1e6fPLG0zWMCEVDhD0VKK6DPdJeesRxuyqL6ZoQ9oe7FvIsnkGu/QxWVwl2DZZD 73Z/brHijqXg3sRQGsgeZlsnH5JyBj/ADJZgCablLXHBr75wQmZi1AvsLE9e/h3+U7RMalqqx0TI bo8OXA/9ZTdJnF9zWU9hYcFhHBTPF9fGDdsFIg== </ds:SignatureValue>
    <ds:KeyInfo>
      <ds:X509Data>
        <ds:X509Certificate> MIIGojCCBYqgAwIBAgIQCEZjQ1QTXW74RfN6KsynzjANBgkqhkiG9w0BAQsFADBEMQswCQYDVQQG EwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMR4wHAYDVQQDExVEaWdpQ2VydCBHbG9iYWwgQ0Eg RzIwHhcNcnQwCQYDVR0TBAIwADCCAX8GCisGAQQB1nkCBAIEggFvBIIBawFpA9F3MCIUVBgIMJRW juNNExkzv98MLyALzE7xZOMAAAFoqfUjCAAABAMARzBFAiEA8Y+6hfyOjPq5xwPKWZJ6UGSqzRJP 2Po9+QIhKBWmBVACIBQf58KiHRriBBtgn+StNss8N50jLSwO99x5DqiMHrwNAHcAh3W/51l8+IxD mV+9827/Vo1HVjb/SrVgwbTq/16ggw8AAAFoqfUjvAAABAMASDBGAiEAhknsy9bPNym7soYpnyHR 1HBrSjj+rJ+XGBWJcCEvMOECIQDv23EuXWzP8ZXKEeSqUjgOp1N1g3LqL0HnTH0M7j7OHAB2AG9T dqwx8DEZ2JkApFEV/3cVHBHZAsEAKQaNsgiaN9kTAAABaKn1JEMAAAQDAEcwRQIgKV7bkMQCNflg tZRKcXxKaTAQ4ek7ivuJEX1oTzWS9dwCIQCdx5ClLr7obmZBf+aUWUXE8Crc8wx3f2PBDaosDg/Y GjANBgkqhkiG9w0BAQsFAAOCAQEAzZ0vMD5QQybCu2sg9/gNR7v2sXyuq2qDb0ewJqL0n+s+ikN6 Gz0Ck+jMjBB+pLJrTmc2XbDJcfzj3BBbe0lAfqEKZHZNxpHj+cZg/6NbPFLBfWfyiQm18yGoj7sS hiB/bxAyKah48l0k7uCG4u+WOsvO9edQ+3WjLl7u7oneLqB2mXSccz545tUQJyTFZUVdaTI7E7cy vmHkx2ubL1gnvSAQ/h5huCoc4zoFHWLdkfDpJzYwjm/rXWfhanaxYlTlYb7ExD09RuUrMS0ahcLt K2nRAx7CD6oLdH6LTCuuZNaaQloK1QBRQWSr5X1Q5v56/VeMVEs8/qd/28y+a4G+Fg== </ds:X509Certificate>
      </ds:X509Data>
      <ds:KeyValue>
        <ds:RSAKeyValue>
          <ds:Modulus> oHlWBuw1PvoVYX3NL9qkYz33NyU34PUI6BWIiUiab8zh/qe17nAAMCgHxJYw5g2h8WJiZBhDPdlr pREMLHoMd6xkgXFKWVUZh+TE/Kxp7D1YCvvDd0WlOqvvrEkuPi1iRBXQLj3xopwKY7INzvwnKykw QxcV+y50B1E+oV8oHD0c+ZTN1NRGWCfFLPoRhIShIG5QaPpQy1h9E74BO2VohQPhkj9hwRC7qTIb pKXztQi0T2BERs/iDxEEHa9xzY0AjBEqvUoZ8iqbd4IoqcF0+ryWwP+rCR9FPy43aW+U0mvYn2KT N+MA0JSdhLrAD9h1KKQIpXnL64W7QDexiJaXUQ== </ds:Modulus>
          <ds:Exponent>AQAB</ds:Exponent>
        </ds:RSAKeyValue>
      </ds:KeyValue>
    </ds:KeyInfo>
  </ds:Signature>
  <samlp:Status>
    <samlp:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success" />
  </samlp:Status>
  <saml:EncryptedAssertion xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
    <xenc:EncryptedData xmlns:xenc="http://www.w3.org/2001/04/xmlenc#" Type="http://www.w3.org/2001/04/xmlenc#Element" >
      <xenc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes128-cbc" />
      <ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
        <xenc:EncryptedKey>
          <xenc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p" />
          <xenc:CipherData>
            <xenc:CipherValue>QcN9dKFTAxtXQEWlh20el91EDQy4bTgX2TNDZnqgS2MfCHngdFPXEzmQC3v7w7YTxrHVx8L/aOee YjJK1CC63E1RcD4qKUmrWHDqqGO3RszSMcdWeKDndzlFbj9Z3TsFmVmVQEsL/pryg6nJAYd6jQrC FLzHlTSUKqXxS9Rl9VI=</xenc:CipherValue>
          </xenc:CipherData>
        </xenc:EncryptedKey>
      </ds:KeyInfo>
      <xenc:CipherData>
        <xenc:CipherValue>uzUj1tGAK5FDBgUfUVCAKYBdnsGOQc9dcDoD5hGM6P/Pr6BvqheXamo3N1qeqUkEJfbpx0nXYMcQ icqL44JGxy3F8L+z9dWy0EATu+MjKLAtb2F3A6u5VJ/PMUGYJLriqfRb/RI/8FOEsOjJn7hqeXwA 74Kd0D+w7E1mRJYIMlJ+E8OlZYy9ETx9n55infrFElp3b1w9nKwJc38wFksG7s2HBQGDWhmeA1po urZSytpkRCOxcgMOuEYBg7mgAD8wIaRqW1+JarlsdpfB2uQJyCGmzhfq5F8jJYv/3ITyI7zW+fc8 Dhq2pFVMxT9A6ErlCyek0fsqmEoSExSVlGBRvTLBSzHKqV+fM22BrvLfh8dKXLXCmzcs/NDTTqCo on0A93DnttEcfLlhS92JoCt4HGb7buvrEoQgVrO50ntxW/4sDAUGSAspGnciXxtDGcsJ53qpgrJn Sfnf2Y31jVUHTWAwN9aYza1r9U0wgUStUTzgwi2UoAdAy44XKK8fCYgcg/ssjDkBj4xkz6ZMVYEz Xl8anejVrCCzyXU0CmeCXq2beLWkQqa+xINzRnKESXxQ4KtrbEcY3ntXOAw0UQDC1khAiqnDVpbo A+YD3KfhfoRb3kfrppQ1GG58lPIsjyhfR1iF5zAnmEGxz7UB9hO k8prEzVxRylxJ2I/23hnlOb31v9MysXvJ+7rS/JgmOjETnTKR6ykZyoBluwpHEfgBY1/phPnCbgq LMIdWMVtzxFIBmrwZqrAXGo/Ye2pvikPg3nSkQmyWqi3z8Y5LpOTxo7GoL0nFVMKWA3usJpMB7i7 k3z2/w6TDWtDqxalN9bl2tywbmko6NBFXPQKc10mGUl0JWDAmSX0WIpsV/UxZCezsN7/AvgkkPCR kCGM4D63AWcryUNLW1vqKLu1PfSCIHEFfRxR3urvMDyRjFKwH2bwdrPd9fdl19N5gRX62tJfiAGL J8zthI/x3Eaehpk/L/v2PiG2vlAXFu7w175OykX+9CS+Ab/JLwBgLvUEa26m3n26j6v8ymFonFu9 dsL5gQTgaCx8X+uU1ZCaJ2wzpbedP1MWMdtn8Ah9Zw0Ia9fBf7PWYLt2Az8Q1usLrx8+cw92o1Oe tZD9GH96+MeVVVYZK1oXYxt35CN6FZ7zOtzb0Hn89WNBvh5dcSxqzpwq+HbZkO0aUyMh8H8BrZjf +O3r3EvxnatIik7ECsActSwdo+P88XkNsqx/Va7UEDR8VwwD0+/GcVoOSxDzZD8LCJkyVO9ou5ec OsWbW+w+BnZCPCLtPy3Wt0xcP/PZPByPxyUCvSWptnMdVx/8prXl5GmBhHdjVQl+L8I/MhJFMio3 zYzuZnbiAuSoKff8uKeDJnHoMPUxezqM5JLSGRlosZ2XM5uUc0xAmxJUkMqoYQTvHeRYJ/DRqlY5 LjFWuuNImFFADHUg/2+4a0NaWuF3KD7BSwYTTqQVKWAGUfeY0oWO+EFDFLaL8tmX1LDVhJou5740 P1mI8xVgQs8zUp5R3N4YJrZ2tCZ6l/0/PCitJDPmwOtFj4wlI3V/gBJ2Xzsr8SJ0iqNruD1YHBqv iupC/5hErhyXNt08MMLrscf+Ui8yJwGzmFZjMdlhtnoSWL9/+3g4F95dMXYgdDKHnnhmVl5JLJp2 O5bp3s2V5Mw0qvazKVwliNxsym48eA4GFkOTE1rCH/OE/k6IXsu2l2mOIEhf3gVsZGR7616bnz3X TKFX/BFj4PeNRLeGZA2LVM/ih2Kt0Tkxc7OXycIWaXRjFzkr4SFJ2INNoQMcxwgx8W5hja5fBeyV b51ukhyUiarAmlh/H0cRCDjsQvsYne7guZM0B4JM/YB111sqsqL8bkfFCVkRXDMFNYQitIQRc5lD HMT3FU6OZlEAL9uBdeQcuCVaqCkiO0x5o2N28VsL1ojm6PpZWV7x6cAB43E/qp3h3Wh/95mXgDu1 Y0GDlRQfzzQTvq2nRuODJmZ2fm18v1vW+FTnIXIyD7bb5nj6XyAp9cQqQNibT0RZDicM67X3SVBF Map0CmDTF9ExYZuFzDyVW2ycVuOA2XPmKs42N9kRMLCr8OU1H4B6qmbNkY+1cZMVrXb1rs+ynFsW uaqhysH9gdnggPuY1cG9FBq/nydlM1CMmxZe8JFs7sibzGISu/m01Usvpd3kR4wXE1BGehuNRmC4 S6k0RDpVjkCS+8Ebyd+Oy8pq3E36mkdXvz5uJKqoLyj2vF+MQPiz7TWv3bGUUl8Y6i1qEM7PN6KP tVZHrhGuH2LGomJi9kq4W1+yzxMziimHWrB4g2IPzGVnHEGPwc8RrDnaWQ8URrVKqCHifRq5aAW9 aVo/Nw7Q7bvHt6S8uwcfssGQ6VFmLrJtuTKTwgfqHaQMdEyGcU7Rmk/mCkyfz4zY3MLwHaT/FQAe YjsZsV/crI3PrdyGE007p3vVaaMtV+5+ANeChoMWvu8uVGsuWrqYLnr6F4LmGtWUumu3JMqyshCX ZshWrpp153RTbfrjYeQDZmEwqtCDaMYQ4V2XXL4vKBQXUwwizYbdeCUudW1QTa6VaP7uLZrcmrnS ImjDP5g9NNIpW8/HjI9Hj7+QIaTwYSYaHFyS3mkpfsRQ+YLkqjKQWMSM3virlgYUsM3iq6wd7S8A CucBE4K+ma68aLcLLwELhybBcu9ozJXV6R/huf9S5MA9X8hJb7YZtjtxelWu3enHHzxDgGzF6dBQ r7bHvQVKdCo9DQ59zKSLRtc/VIyBh5uN4ri0Ly0plgRCnKC5EbYrlilo0rslG3tjBdFAnp6piZsp 6o0kJXiD1z3VDhP0dt9wxl3NIp00fBQAsOce0wZl1Sr86lkUhyOHHPbImP6mmcqAxePbzhTdqXA2 bIIDFWVi65weToWIjBHQ3iXa/VCoRG/4np93fC7WwWLToV4gS2YTC00zxBetPZmYDQcHGFaDHjqU MDh20GfHZBvFB163QjbP13F872MPIyNfwXJP1a4VdgNoFm+2bdiHqHouKTllrnHKidTK8Kp/T3Qu OPSJJG1/kefkg0MrBltBjLQegvmHQVh5B43mhY+TOcadUJH15NrUUk8QdPB3dZLC4BfNrF4Y61L/ SZXSr503pKKvPmKLYDrp6DOxY7l7reZDk4qCKRYoppvnfl2hhQ9XiiWfQliQ7gm5cXGA7eiENW3r SDM+5dlam9f9mNf36QTvI4VIQzpguQ62HoFl0k2w5VAyCB5auwMsdp2MYvCOoVXo2S/Ld0LpDaeL DcKlM7w9b4TsuaDhESgGGD+270g0Ub6e0Af8jRi0a0kYy782t4hCF8Ha2xmHeZoOexxt0dIF+pZT 58fcnS1kRQRIpaFm67TNZ3exp7T2PfD/NOha5b63yXIFER8HoJp3C/MVx3wzRqZkfSZ1ejx1ugXG E94h0ggY8lR2HAhqvLTSvlEZWvCXpIsToW+TGdFR54FtZ2lMzctN68z87IzHNZovg1Lugt93F5qj FoBwD4ws1t6yK11wZUvNQ0kqOnpwaC8wpYrLo9bumGKm5x/1pKc6V28ne7aED9aU37cvka0BNib0 0Qb8crfR3XxnLPhkqMXWSPkGpxIPr6RdbAskF1RY1fJpOsro1dxrXfScxOVfRl6TWCPZlJkUKQtL w9bLc0Fb6FcNMJ+276MoTII58POamQ==</xenc:CipherValue>
      </xenc:CipherData>
    </xenc:EncryptedData>
  </saml:EncryptedAssertion>
</samlp:Response>