Introduction to Cryptography

Cryptography is the study and practice of techniques for secure communication in the presence of third parties called adversaries. It deals with developing and analyzing protocols which prevents malicious third parties from retrieving information being shared between two entities thereby following the various aspects of information security. Secure Communication refers to the scenario where the message or data shared between two parties can’t be accessed by an adversary. In Cryptography, an Adversary is a malicious entity, which aims to retrieve precious information or data thereby undermining the principles of information security. Data Confidentiality, Data Integrity, Authentication and Non-repudiation are core principles of modern-day cryptography.  

History of cryptography

The word “cryptography” is derived from the Greek kryptos, meaning hidden.

The prefix “crypt-” means “hidden” or “vault,” and the suffix “-graphy” stands for “writing.”

The origin of cryptography is usually dated from about 2000 B.C., with the Egyptian practice of hieroglyphics. These consisted of complex pictograms, the full meaning of which was only known to an elite few.

The first known use of a modern cipher was by Julius Caesar (100 B.C. to 44 B.C.), who did not trust his messengers when communicating with his governors and officers. For this reason, he created a system in which each character in his messages was replaced by a character three positions ahead of it in the Roman alphabet.

In recent times, cryptography has turned into a battleground of some of the world’s best mathematicians and computer scientists. The ability to securely store and transfer sensitive information has proved a critical factor in success in war and business.

Cryptography has been subject to a variety of restrictions in many countries, ranging from limitations on the usage and export of software to the public dissemination of mathematical concepts that could be used to develop cryptosystems, because governments do not want certain entities in and out of their countries to have access to ways to receive and send hidden information that may be a threat to national interests. 

Cryptography techniques

Cryptography is closely related to the disciplines of cryptology and cryptanalysis. It includes techniques such as microdots, merging words with images and other ways to hide information in storage or transit. However, in today’s computer-centric world, cryptography is most often associated with scrambling plaintext (ordinary text, sometimes referred to as cleartext) into ciphertext (a process called encryption), then back again (known as decryption). Individuals who practice this field are known as cryptographers.

Modern cryptography concerns itself with the following four objectives:

  1. Confidentiality. The information cannot be understood by anyone for whom it was unintended.
  2. Integrity.The information cannot be altered in storage or transit between sender and intended receiver without the alteration being detected.
  3. Non-repudiation. The creator/sender of the information cannot deny at a later stage their intentions in the creation or transmission of the information.
  4. Authentication. The sender and receiver can confirm each other’s identity and the origin/destination of the information.

Procedures and protocols that meet some or all of the above criteria are known as cryptosystems. Cryptosystems are often thought to refer only to mathematical procedures and computer programs; however, they also include the regulation of human behavior, such as choosing hard-to-guess passwords, logging off unused systems and not discussing sensitive procedures with outsiders.  

Examples of cryptography

End-to-end encryption in WhatsApp is a prominent example of cryptography encryption these days. This feature is available in WhatsApp via the asymmetry model or public key methods. Only the intended recipient is aware of the actual message. After the WhatsApp installation, the server registers the public keys, and messages are transmitted.

Digital signatures are the next real-time application of cryptography. When two clients must sign documents for a business transaction. However, if two clients never meet, they may not believe each other. The use of encryption in digital signatures then ensures improved authentication and security.

Cryptography concerns

Attackers can bypass cryptography, hack into computers that are responsible for data encryption and decryption, and exploit weak implementations, such as the use of default keys. However, cryptography makes it harder for attackers to access messages and data protected by encryption algorithms.

Growing concerns about the processing power of quantum computing to break current cryptography encryption standards led NIST to put out a call for papers among the mathematical and science community in 2016 for new public key cryptography standards.

Quantum computing, in contrast to conventional computing, uses quantum bits (qubits), which may simultaneously execute two calculations and represent both 0s and 1s. NIST claims that even though a large-scale quantum computer may not be constructed in the upcoming decade, the current infrastructure requires the standardization of publicly known and understood algorithms that provide a secure method. The submission deadline was in November 2017, and it would take three to five years to analyze the plans.

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