Digital Signature

The use of a mathematical technique to confirm the origin of information, and to confirm that it wasn't changed since it was written. Digital signatures may be used with software downloads to make sure that the software you're installing is the same as the official published version, and that nobody has tampered with it. They're also often used on encrypted email and for many other purposes. When information isn't protected by a digital signature, an Internet service provider or other communications provider could change the contents of what someone wrote or published, and there wouldn't be a technical means to detect that this happened.