Store encrypted passwords with connections.

Closes #22 as encrypted password is now deleted as part of the connection record.

core/KeyStrengthener.h

@@ -0,0 +1,29 @@
+#ifndef KEYSTRENGTHENER_H
+#define KEYSTRENGTHENER_H
+
+#include <QSqlDatabase>
+#include <botan/pwdhash.h>
+#include <botan/secmem.h>
+#include <memory>
+
+class KeyStrengthener {
+public:
+	KeyStrengthener() = default;
+	KeyStrengthener(std::unique_ptr<Botan::PasswordHash> hasher, Botan::secure_vector<uint8_t> salt, size_t keysize);
+
+	KeyStrengthener(const KeyStrengthener&) = delete;
+	KeyStrengthener& operator=(const KeyStrengthener &) = delete;
+
+	KeyStrengthener(KeyStrengthener &&rhs);
+
+	KeyStrengthener& operator=(KeyStrengthener &&rhs);
+
+	Botan::secure_vector<uint8_t> derive(const std::string &passphrase);
+	void saveParams(QSqlDatabase &db, const QString &table_name);
+private:
+	std::unique_ptr<Botan::PasswordHash> m_hasher;
+	Botan::secure_vector<uint8_t> m_salt;
+	size_t m_keySize;
+};
+
+#endif // KEYSTRENGTHENER_H