(The Gist of Science Reporter) Cryptography [FEBRUARY-2020]
(The Gist of Science Reporter)
Secured concern for diplomats, military and other officials over the
ages. Even if it’s exact origin cannot be traced back communication has
always been an area of precisely, its importance can surely be understood
from the fact that even the greatest rulers like Julius Caesar had such a
method for information exchange popularly named after him as Caesar Cipher.
The process of securing information by manipulating it in such a way
that makes it incomprehensible for people unaware of the secret is called
cryptography. Cryptography is a combination of two Greek words, kryptos
meaning secret and graphein meaning writing. So, in other words cryptography
can also be called secret writing.
The technique is mainly based on a set of steps to be followed in a
sequential manner to achieve the incomprehensibility. These steps together
constitute an algorithm. The algorithm takes a meaningful information known
as plaintext and converts it into a gibberish data called ciphertext. Mostly
this conversion might require an additional piece of secret information
known as a key whose knowledge is essential for securing and revealing the
information. This process is known as encryption and decryption
Depending upon the period, cryptography can be broadly categorised as
Classical cryptography and Modern Cryptography.
Classical cryptography refers to the early form of the methodology which
was mostly dependent on the rearrangement and the substitution of the
letters in a way that the output could not be understood without the prior
knowledge of the process.
These forms of cryptography were very popular in ancient Egypt and
Greece. The popular Caesar cipher is one of the oldest examples of the
substitution cipher in which the letters of the plaintext were replaced by
the letters in the alphabets starting from any specific place in the
Example: Let us assume that we replace each letter in a given plaintext with
a new letter obtained by moving three places from the current letter in the
English alphabet to obtain the cipher text.
Modern cryptography is primarily based on mathematical calculations that
are easy enough to be carried out by a computer using a key but hard enough
to be guessed in the absence of the same key. Claude E. Shannon is
considered to be the father of this mathematical form of cryptography that
led to the origin of the modern ciphers.
Current cryptosystems work on the Kerckhoff’s principle which emphasises
on exposing everything related to the cipher in the public domain (including
the algorithm) except for the key. This means that the actual security of
the data relies on the strength of the key used for encryption. Hence, for a
modern cipher that is free from any design flaws, the length of the key used
(in bits) will actually give an idea about the number of possible keys to be
tried in order to break the security.
For example, if the key length used by an algorithm is 8 bits then there
would be 28 i.e. 256 possible key combinations that need to be tried in
order to reveal the information using brute-force.
Symmetric Key algorithms:
These are algorithms that use the same key for the encryption and the
decryption process and hence require the key being shared among all the
individuals who need to have access to the data. Since the secrecy
completely depends on the key being used, any accidental disclosure of the
same to non-authorised individuals might lead to compromise of the entire
This problem of safe key exchange is the greatest challenge associated
with this method making it suitable only for securing data for an individual
or a small group of people when this approach is not associated with any
other special protocol for information exchange.
Example: DES, AES-128, AES-256, Blowfish, IDEA, Twofish, etc.
Asymmetric Key algorithms:
These are algorithms that use a pair of keys for the encryption and
decryption of the data – the keys are known as public key and private key,
respectively. The private key is kept a secret with the owner and is used to
decrypt the data encrypted with the public key made available to everyone in
the public domain. Another use of this type of algorithm is for user
authentication where the data encrypted with the private key can be
decrypted with the public key to verify the fact that only the owner of the
private key can encrypt the data.
Since this type of algorithm doesn’t rely on a single key for security,
it overcomes the limitation of the symmetric key algorithms and is used for
information exchange on the internet as a part of various information
exchange protocols. One of the major limitations of these algorithms as
compared to symmetric algorithms is that they are computationally expensive
hence using them frequently within a process is not easy.
Cryptographic Research in India:
Cryptography along with information security being one of the hottest
topics in the current times has made a huge impact within the Indian
research fraternity as well. India with the motive of gaining excellence and
promoting knowledge in this domain has set up some of the world’s best
institutes like RC Bose Centre for Cryptology and Security at Kolkata.
Organisations like Cryptology Research Society of India (CRSI) and
Scientific Analysis Group (SAG) of the Defence Research & Development
Organisation (DRDO) also do a lot of research in this field. The popular
international cryptography conference called Indocrypt has been organised by
CRSI every year since 2000 for the promotion of cryptography in India and
Specialisation courses in cryptography and its associated fields are
also offered at various IITs like IIT Kharagpur and IIT Madras for
youngsters seeking a career in this domain.
There is a need for official guidelines from the government on the
standardization of the algorithms and cipher suites to be used to safeguard
the personal data collected by the government and private entities from
individuals so as to ensure a minimum level of standardised data security
within the country. And of course, spreading awareness of the subject among
the people is very essential to remain happy, healthy and safe in