What is Cryptography? - Definition & Uses

Instructor: Lyna Griffin

Lyna has tutored undergraduate Information Management Systems and Database Development. She has a Bachelor's degree in Electrical Engineering and a Masters degree in Information Technology.

In this lesson, we will examine the interesting world of cryptography. Securing our data and systems from malicious intruders, system glitches, and human errors have become paramount in modern systems.

What is Cryptography?

Cryptography is defined as the system by which data and information of value are stored or transmitted in such a way that only those for whom it is intended can read, interpret or process it. Effectively, cryptography obscures information from unauthorized snoopers and interceptors. In the same way, it can be used to hide dubious and clandestine activities in our modern cyber world today. Let's examine the important aspects and uses of cryptography.

Uses of Cryptography: Secrecy

Data Transmission

Data is at risk when it is in motion (during transmission). The risk occurs when unauthorized persons attempt to intercept, copy, modify, corrupt or delete the data. There has to be secrecy in data transmission, which is one of the uses of cryptography. Transmission always involves two parties: a sender and a receiver. For the secrecy to be effective during transmission, the data has to be encrypted (encoded) from the moment it leaves the sender until it successfully reaches the receiver. Encryption is defined as the process of converting data from the normal, readable format into an encoded format which is unreadable by others. The encrypted data can only be accessed and read by the parties in possession of the decryption (decode) key. Figure 1 shows cryptography in data transmission with the sender possessing the encryption (Key A) and the recipient possessing the decryption (Key B).


Data Storage

Data in storage refers to data at rest (on a storage device). Our storage devices are very sensitive. In our current society, computers have practically been replaced by smart devices. This means that these devices contain tons of sensitive data from our daily activities. Secrecy in storage is achieved by storing of information in an encrypted form. This way, unauthorized intruders to the system will be presented with gibberish as data, thereby preventing any data compromises. In the absence of the correct key, the data is inaccessible. The user possesses the key to access the data. Data is arranged in files and folders on computers and devices and individual levels of secrecy can be applied. Keys should be changed on a regular basis and offsite to maintain security. Data in use while on the system, however, is not encrypted. This is a point of vulnerability of data on the system.

Uses of Cryptography: Integrity

Data Transmission

Data in transmission can be corrupted and the integrity of the file compromised. Whether the corruption occurs due to malicious interception or system failure, the possibilities are real and the consequences profound. Data transmissions form the foundation of our modern society. From education to banking to flying planes, data integrity in transmission must be maintained. Cryptography steps in by use of validity checksums. A cryptographic checksum is a digital mathematical value associated with a file and used as a future reference point to verify that the information in the file has not been compromised. In transmission, a checksum is done on the data being transmitted. It is encrypted and along with the encrypted data is transmitted to the recipient. Upon receipt of the data, the recipient decrypts the checksum and uses it to again checksum the data transmitted. If the checksums agree, the data is intact and integrity is preserved.

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