The Enigmatic World of Cryptography
Ehlol, ohw rae oyu? Ti si rgeta ot ese oyu, edra erdare!
Wait up! Before you think that you have clicked on an article written in gibberish, listen to me. I want to assure you that you are on the right website and correct article. But then what is all that in the first line? Allow me to explain – the first line of this article is saying “Hello, how are you? It is great to see you, dear reader!” Stunned? Don’t be! This is what today’s article is going to be about – Cryptography. Let’s delve into it.
What is Cryptography and why is it required?
Cryptography is the practice of using various techniques for secret and secure communication. Its function is to prevent third parties or unauthorized persons from getting access to private messages.
When we use a public messaging platform such as WhatsApp or ecommerce websites for digital payments, our personal data such as card number, CVV, message contents, etc. are private and hence need to be protected from getting into the hands of unauthorised persons. This is when the process of encryption comes into place. Hence, we can firmly say that cryptography is the cornerstone of modern digital world.
The Process of Encryption
Before we go into understanding how cryptography is applied in our daily life, it is important to first know some of the technical terms –
1) Plaintext – It is the message that you need to send securely. It can be in any language that humans use. For example – this article is in plaintext form as it is in English.
2) Encryption – It is the process of applying cryptographic techniques to plaintext data in order to convert a message into a secure form. This is done by using an ‘Encryption Key’. This key can ‘lock’ the message such that it cannot be read by someone with no access to the ‘key’. This encrypted message can then be sent over a public network, such as internet, without the fear of anybody accessing it without proper authorization.
3) Ciphertext – When plaintext is encrypted using an encryption key, it is converted into a ciphertext. Thus, in the aforementioned example, while ‘you’ is the plaintext, its corresponding ciphertext becomes ‘oyu’ through the method of jumbling up the order of letters in a word, technically known as Transposition Cipher.
It is also possible to use Substitution Cipher wherein alphabets in a word are replaced by other letters. Thus, by substitution, the word ‘hello’ can be written as ‘imffp’. If you closely observe, I have replaced the letters in the word hello with the alphabets just after them. Hence, the key for this ciphertext is ‘letter+1’. This is the simplest example of ciphertext, but cryptography involves encryption using more complex methods that use sophisticated mathematics for encryption.
4) Decryption – While encryption is performed at the sender’s side, decryption is the process of converting ciphertext back to plaintext at the receiver’s end so as to reveal the original message. Theoretically, no person who is not in possession of the encryption key can decrypt the ciphertext, thus ensuring the establishment of a secure channel of communication between the sender and receiver, regardless of the use of a public and/or open network.
This is because even if the message falls into the hands of an unauthorized person, that ‘man-in-the-middle’ would not be able to decrypt the message and access its contents. Decryption can only happen at destination where the receiving device has a decryption key. Thus, decryption is like opening the locked message using a duplicate key at the other end.
Evolution of Cryptography
Perhaps, cryptography that enables secret communication between two parties, is the only modern technology whose roots go back to the classical times. The term Cryptography has been derived from the Greek word kryptos, which means hidden.
In modern times, the field of Cryptography is an amalgamation of concepts used in mathematics, computer science, information security, digital signal processing, etc. Yet, there have been many techniques in use since ancient times. For example, Sage Vatsyayana of third century India mentions two types of ciphers called Kautiliyam and Mulavediya. The former substituted vowels for consonants while the latter defines pairs of letters which were then substituted for each other in a sentence. Similarly, the Sassanid empire in Persia made use of two scripts – one for official correspondence by the king and the other for communicating with other countries secretly. Arab historians mention many different types of ciphering methods that were employed by the Persian Shahs for covert communication. Analogous examples can be found in the foregone civilizations of Greece, Egypt and Italy too.
Thereafter, cryptography continued to evolve, thus taking the form of mechanical rotor machines used by the Germans during World War II. With the advent of computing machines, cryptography changed shape since the 1970s. As the computers become more powerful and ubiquitous, the processes and techniques of encryption continue to achieve greater sophistication. On the other hand, increasing access to high computing power devices has also posed a challenge to the field of cryptography. Highly competent computers can be used to easily break into the encrypt or decrypt key, thus compromising the security of the transmission channel. To solve this irony, quantum computing is being looked at as a solution due to the non-binary values that a quantum bit can take.
Modern Cryptography –
Modern cryptography is characterised by the extensive use of computers and software algorithms for encryption and decryption. Following two types of cryptographic methods have emerged in the recent times –
1) Symmetric Key Cryptography –
This method uses the same key for encryption of plaintext into ciphertext and in decryption from ciphertext to plaintext. What this essentially means is that the plaintext is first converted into a string of binary values – 0 and 1 – that the computer can understand.
Next, a key that is also shared with the decryption machine, is used to perform a series of mathematical operations on the plaintext in binary form. Then, as this encrypted data travels and reaches its destination, a reverse of the mathematical operations that were earlier performed for encryption are done on the ciphertext. Because the same key is used for reverse operations, the plaintext is revealed before the receiver, thus fulfilling the purpose of cryptography.
As every secure transaction between each pair of communicating devices requires a unique key, the number of keys that are required rises manifold, thus making generation, transmission and management of billions of keys complex, time-consuming and prone to errors and possible security lapses. Also known as Private Key Cryptography because of the secretive nature of key used to encrypt and decrypt data, this type is mostly applied for transmission of data – for example in satellite communication, for defence applications, etc.
2) Asymmetric Key Cryptography –
This type is also known as Public Key Cryptography as out of the two different keys used for encryption and decryption, one is made public so that it is accessible to anyone. Though, this technique seems counterintuitive to the very definition of cryptography, it resolves a significant problem with the private key algorithm – that of key management.
Even though, the public and private keys are related to each other, it is considered computationally impossible to calculate private key from the public one due to a humongous number of possibilities. Thus, due to use of different keys for encryption and decryption, this type is considered to provide enhanced security, compared to symmetrical key cryptography. Hence it is used in digital signatures, verification of documents, web browsing, etc.
Characteristics of Cryptography –
1) Confidentiality – this feature ensures that no unauthorized person is able to access the data.
2) Integrity – cryptographic techniques make sure that the received data is same as that was transmitted and that there was no data impersonation or discrepancy.
3) Non-Repudiation – this feature is important so that the sender cannot deny transmitting of message. If not for non-repudiation, the features of data confidentiality and integrity would come into question. Hence, this is an important characteristic of modern cryptography.
4) Authentication – this feature allows confirmation of the identity of the sender and receiver so not no intruder can get hold over the information.
Cornerstone of Digital Age
It is an oft-cited estimate that cyber-crime causes a loss of at least 1% of global GDP. If not for cryptographic methods and standards, this number would have been even larger. Hence, it is safe to say that cryptography industry is worth trillions of dollars. This is also because of applications in almost every field of human existence. With the proliferation of Internet of Things devices (click here to read more) and digital payments, the demand for cryptography has risen and shall continue to do so.
In our next article, we shall learn about the legal hurdles in implementation of cryptography, its application in the form of end-to-end encryption of WhatsApp and how it was compromised in the recent celebrities’ drug-abuse case. So stay tuned for next Thursday!
Vishvali Deo is an E&TC (Electronics and Telecommunication) Engineer by education and Software Engineer by Profession. She believes that 'Technology is a Great Democratising and Equalising Force' and hence is on a mission to make the general public understand seemingly complex technologies in a simple manner.
She is convinced that the root of today's world problems lie in the past, hence she has also pursued post-graduation in History. She has a keen interest and a good grip over Economics, Political Science and Environmental Engineering. She has a penchant for working with Women and spreading Digital Literacy amongst them, with the aim of their empowerment. She also strives to provide Free Quality Education to children and counsels young adults. Besides, she is also skilled at Public Speaking, having won many awards in Elocution & Debate Competitions and Technical Paper Presentations.