On the website of the Ministry of Foreign Affairs in your own country you will find more information about the travel documents you need for your stay in Egypt, in Dahab.
You also need a visa which costs around 18 Euros and which you can buy at the airport on arrival in Egypt. In Sharm El Sheikh there are counters where you can buy a visa stamp. Buy a visa before you go through passport control!!!
If you only want to stay in the Sinai (Dahab is in the Sinai) you don’t need a visa, provided you don’t stay longer than two weeks. Fill in the card you receive on the airplane or at the airport ‘Sinai Only’. For a visit to Ras Mohamed (Sharm El Sheikh) you will need a visa. If in doubt, ask at the visa offices at the airport.
Note: It’s your own responsability to have the documents you need.