Monday, June 20th, 2016

Cryptography can be broadly defined as the practice of combining mathematical, computer science and electrical engineering techniques to come up with a secure communication process that is safe from adversaries or eavesdroppers.

Cryptography is closely related to data encryption and decryption, with the two being individual processes largely used in cryptography. Data encryption is where a message is changed from plaintext or understandable form to cipher text or coded message which has no clear obvious meaning. Decryption is the reverse of the encryption process. In each of these process, a crucial component called a key is required. Basically, a key is a character set or algorithm used to decipher the meaning of a cipher text so as to get the intended meaning.In cryptography, the key is usually exchanged between the sender and the recipient, still in hidden fashion. This prevents the eavesdropper or third party from understanding the message being passed across.


Cryptography dates back to Egypt in about 2000BC. This first form of cryptography, believed to be in the form of hieroglyphics, is suggested to have been solely for the amusement of literacy enthusiasts and not message hiding of any kind.

Since its discovery in 2000BC, cryptography has advanced well through the centuries. From mere manual encryption and decryption of text passed via plain paper, cryptography over the years shifted into cryptography machines, which were able to encrypt and decrypt confidential, classified messages, in automated fashion.Such machines were very common in World War II, such as the Enigma machine that was used by German forces in both World War I and II. The rapid development of cryptography, especially in complexity during the war led to the development of Colossus, the first computer based decryption machine that was built to decipher messages from the German Lorenz SZ40/42 machine.

In the modern society, cryptography is associated with more than just the security of plain text involving letters and digits. Images, sound and anything re-presentable in binary format, which is the lowest level of language in a computer can be encrypted and decrypted. Modern cryptography covers more than message hiding or confidentiality. Objectives such as integrity, non-repudiation and authentication define modern cryptography computers.

Integrity for instance ensures that the information cannot be manipulated in transit or storage between the sender and receiver. Non-repudiation ensures that the sender is accountable for the message sent or created thus he/she cannot deny the transmission at a later stage. The final objective, authentication, ensures that the sender/ receiver can confirm each other’s identity such that the origin/destination of the message is as intended.These objectives are met via protocols and procedures implicitly referred to as cryptosystems. These cryptosystems guide how information is secured and transmitted over a network. Computer security thus comes under great focus in modern cryptography. Several areas of study exist for modern cryptography. The chief ones are symmetric-key cryptography and public key cryptography.

Symmetric-key cryptography is a situation where the key is the same for both encryption and decryption. This means that how a message is hidden is the same way it is deciphered at the receiver. However, each sender-receiver network has its own unique key. The major problem is where the number of unique keys that need to be generated increases with the square of the number of single sender-receiver networks. This brings about a key management problem. The public key implementation however uses one common key for encryption, but a secret/ private key, only known to the recipient for decryption. This approach reduces the key management complexity involved with using symmetric keys as the number of keys does not increase exponentially with the number of networks.

The internet for instance employs cryptosystems such as the https for secure message and data transfer between sites, especially for e-commerce sites. This security is very essential in protecting sensitive data such as credit card details and private account details of online users. A great security concern arises when cryptography is used for espionage. Several countries have strict regulations on the development of cryptosystems and require that the algorithms be within public domain. This is to ensure malicious computer and cyber-attacks are kept at bay.