BOOL WINAPI CryptDecodeObject(
  __in     DWORD dwCertEncodingType,
  __in     LPCSTR lpszStructType,
  __in     const BYTE *pbEncoded,
  __in     DWORD cbEncoded,
  __in     DWORD dwFlags,
  __out    void *pvStructInfo,
  __inout  DWORD *pcbStructInfo
);

typedef struct _CERT_SIGNED_CONTENT_INFO {
  CRYPT_DER_BLOB             ToBeSigned;
  CRYPT_ALGORITHM_IDENTIFIER SignatureAlgorithm;
  CRYPT_BIT_BLOB             Signature;
} CERT_SIGNED_CONTENT_INFO, *PCERT_SIGNED_CONTENT_INFO;

[DllImport("Crypt32.dll", SetLastError = true)]
        public static extern Boolean CryptDecodeObject(
            Int32 dwCertEncodingType,
            string lpszStructType,
            Byte[] pbEncoded,
            Int32 cbEncoded,
            Int32 dwFlags,
            Byte[] pvStructInfo,
            Int32 pcbStructInfo
        );