Encryption protects e -mail by rendering it very difficult to read by any unintended party. Digital signatures can also be used to authenticate the origin and the content of an e -mail message. In some cases cryptography allows you to have more confidence in your electronic transactions than you do in real life transactions. For example, signing documents in real life still leaves one vulnerable to the following scenario. After signing your will, agreeing to what is put forth in the document, someone can change that document and your signature is still attached.
Cable TV is set up so people can watch only the channels they pay for.
Since there is a direct line from the cable company to each individual subscriber's home, the Cable Company will only send those channels that are paid for. Satellite TV works slightly differently since the satellite TV companies do not have a direct connection to each individual subscriber's home. This means that anyone with a satellite dish can pick up the signals. To alleviate the problem of people getting free TV, they use cryptography. As seen, cryptography is widely used.