Question One: With the realization that people needed to share information with each other, devices were innovated to make this information private. The field of cryptology helps in creating and deciphering such coded information. The growth of internet and e-commerce has made cryptology an enormous growing filed today. Many changes and innovations have continued to be made in the field. Efforts are made to continue to maintain information securely. Unfortunately, there exist people who are always on the lookout for loopholes in the advances made in cryptography. As with other technologies, there are vulnerabilities in some areas of the system as they are tried and tested (Wobst, 2007). Many people hack systems that have been encrypted in order to access confidential information and use it for their advantage. This includes people’s private emails, messages, financial information, etc. it is therefore a never ending cycle of secure cryptology been developed, others trying to find loopholes in such systems and more developments made to address the loopholes and make the system more secure.
Question Two: Symmetric-key cryptography refers to a method of encryption that uses a single key for both the encryption and the decryption. The receiver and the sender use keys that are related. The major drawback of this class of algorithms is that both parties are required to have accessibility to the secret key (Das & Madhavan 2009).The most common symmetric-key system is the Data Encryption Standard. It is useful in various applications such as email-privacy and encryption of ATMs The public-key cryptology uses two different keys. One key is private and functions to encrypt messages. The other one acts as a private key and functions to decrypt messages. Public-key cryptography solves the drawback of symmetric-key cryptography by creating a system whereby the public key is distributed to all. The private key for decrypting the information is however maintained in secrecy. A range of data formats and protocols use public-key cryptology. For instance, it is used in the packaging industry for digital signatures. It is also used in PDF files that are digitally signed; including the attachments therein (Das, 2009).
Question Three: Protocols are put on top of each other in layer form in networking. Each layer is responsible for different communication aspects. There are seven layers. The first, the physical layer, passes on and receives bits from the connecting medium. The data link layer then follows. It is responsible for transmission integrity and the node-to-node validity. Example, ATM and Frame relay (Walke et al, 2003). Next is the network layer which acts as a medium at the switching points between the sender of the message and the receiver. A good example of this is the TCP/IP and other routable protocols such as IPX and SNA. The transport layer then follows and is in charge of the overall transmission integrity and the end-to-end validity. The session layer coordinates communication efficiently and in an orderly manner. Most of the services are usually infused into the transport layer. The presentation layer is the sixth layer. It negotiates and manages the ways in which transmitted data is represented and then encoded. Good examples are XDR of the Sun and ASN of OSI (Walke etal,2003). The final layer is the application layer which manages the language and the syntax that programs utilize to communicate effectively with other programs. Common functions of this layer are file opening, file closing, file reading and writing, file transfer, etc.

References
Das, A., &Madhavan, C. E. V. (2009). Public-key cryptography: Theory and practice. Upper Saddle River: Pearson Education.
Walke, B., Seidenberg, P., &Althoff, M. P. (2003).UMTS: The fundamentals. Chichester, West Sussex, England: Wiley.
Wobst, R. (2007). Cryptology unlocked. Chichester: John Wiley & Sons.