Implementation of an abstract class with a function that returns a shared pointer

Question

I need the implementation of the following abstract class. So that it can successfully compile with another code that uses functions from the abstract class. I mostly need the part on the shared pointer.

Here is the code

    #ifndef CRYPTO_HPP
    #define CRYPTO_HPP

    #include <functional>
    #include <memory>

    enum class Algorithm
    {
      eNONE,
      eCAESAR,
      eAES,
      eRSA,
    };

    class Crypto
    {
    public:
      Crypto(std::function<void(const uint8_t *data, uint32_t len)> encryptCallback,
     std::function<void(const uint8_t *data, uint32_t len)> decryptCallback);

      virtual void genKeys() = 0;
      virtual bool getKeys(uint8_t **pubKey, uint32_t &pubLen,
                   uint8_t **priKey, uint32_t &priLen) = 0;
      virtual void setKeys(const uint8_t *pubKey, uint32_t pubLen,
                   const uint8_t *priKey, uint32_t priLen) = 0;
      virtual void destroyKeys() = 0;
      virtual bool encrypt(const uint8_t *data, uint32_t len) = 0;
      virtual bool decrypt(const uint8_t *data, uint32_t len) = 0;
      static std::shared_ptr<Crypto> cryptoFactory(std::function<void(const uint8_t *data, uint32_t len)> encryptCallback,
                                           std::function<void(const uint8_t *data, uint32_t len)> decryptCallback,
                                           Algorithm algorithm);
    protected:
      /** @brief Encrypt callback function */
      std::function<void(const uint8_t *data, uint32_t len)>m_encryptCallback;
      /** @brief Decrypt callback function */
      std::function<void(const uint8_t *data, uint32_t len)> m_decryptCallback;
    };

    #endif /* CRYPTO_HPP */