An encryption method that is largely transparent to a user is accomplished by intercepting a change document or open document command, carrying out an encryption or decryption process, and then completing the command on an encrypted or decrypted file. The encryption method can be used in a wide variety of environments, such as an individual computer program, a database or electronic messaging over the Internet. The encryption method can select from a plurality of encryption algorithms. The encryption method can also allow just a portion of a document to be encrypted, placed in a container, and then be represented by an object linking and embedding ("OLE") container object or other representation supported by the file.