Lab tests have confirmed the authenticity of the letter purportedly written by kidnapped soldier Gilad Shalit and sent last week to his father, Israeli officials said Wednesday. The officials also confirmed that Egypt was mediating a swap in which Israel would release hundreds of Palestinian prisoners for Shalit, who is being held by Hamas terrorists. Livni: Abbas 'partner' in obtaining Shalit's release The inside sources who confirmed the details, however, spoke on condition of anonymity because they were not authorized to speak to the media. The Prime Minister's Office declined comment Wednesday. In the letter, handed over to Gilad's father Noam by Egypt, Gilad apparently told his parents that he was well. "I feel fine and am being treated well," the letter read, according to an Egyptian official, Maariv reported Monday morning. "I hope to celebrate my next birthday at home," Shalit wrote. "I miss you and think about you a lot." A report issued on Thursday said a Hamas delegation from Damascus had given the letter to Egyptian officials in Cairo. Egypt had then passed it on to former deputy Shin Bet head Ofer Dekel, who is in charge of dealing with the affairs of the kidnapped soldiers, the report said.