|  | 14.1 | The Presentation Layer
| 14.1.3 | Data encryption and compression
Layer 6 is also responsible for data encryption. Data encryption protects information during its transmission. Financial transactions (e.g. credit card information) use encryption to protect sensitive information as it traverses the Internet. An encryption key is used to encrypt the data at its source and then to decrypt the data at its destination. The presentation layer is also responsible for the compression of files. Compression works by using algorithms (complex mathematical formulas) to shrink the size of the files. The algorithm searches each file for repeating bit patterns, and then replaces them with a token. A token is a much shorter bit pattern that represents the long pattern. A simple analogy might be the name Cathy (the nickname), the token, to refer to anyone whose full name is Catherine.