History of cryptology
10B1 조형우
Cryptography is derived from combination of
two ancient Greek Words krypto meaning hidden and grafo meaning to write.
Therefore the literal meaning of cryptology is “hidden writing” which is
crucial tool for secure communication. Nevertheless, the first intention of the
cryptography was not related to concealing the message, it was utilized to
decorate tombs to make one’s life seem noble in Egypt, around 2,000 B.C.
Cryptology have started from decoration but it developed and started to
function as a tool to conceal messages. This history of cryptology is widely
classified in three eras: from ancient civilizations to 1940s, around Second
World War, after Second World War to modern society.
Cryptography was used for mainly three purposes in the ancient
society which is private communications, delineation of religion and secure
communication for military. The most important function in the ancient period
was delineation of religion and decoration of tombs. For example, in the Book
of Jeremiah, a few English words transformed into other English words:
"hob"="sly", "hold"="slow",
"holy"="slob", "horn"="slim",
"zoo"="all", "irk"="rip",
"low"="old", "glow"="told, and
"grog"="tilt". Furthermore, it was sometimes used for
secrete communications such as Caesar cipher which was used for politic
purpose. This was a method shifting alphabet three positions so that e 'a' is
transformed into 'd', 'f' into 'i', 'z' into 'c'. For example, if there is a
word “Term paper” it will be enciphered to “Whuo SdShu”. So, the plaintext
would be term paper, ciphertext would be whuo sdshu and the key would be
shifting alphabet for three positions. Even though this technique might be seen
easy to decipher, majority was not able to read such codes in the time of Julio
Caesar which made cipher powerful. After Caesar cipher the development of
cryptology was unnoticeable. Nevertheless the French diplomat Blaise de
Vigenère have developed polyalphabetic cipher in 16th century. This
cipher has been called “the unbreakable cipher” and actually has been unable to
be broken for the four centuries. It has been deciphered by numerous
researchers between the end of the 19th century and the beginning of
20th century. Another important, more modern, substitution cipher in
the history of cryptography was The Hill cipher, a polygraphic substitution
cipher. It was the first cipher which enabled use more than two symbols for a
word. Instead of substituting one letter
for another letter, a polygraphic cipher one can substitute a word by more than
a two group of words. This has made frequency analysis (a technique based on
the fact that inside a text certain letters and combinations of letters occur
with varying frequencies). attack ineffective since a word could be substituted
by various words.
As time passed, when it became Second World War, people began to
recognize the importance of machine in cryptography since machine was capable
of making cipher more complicated and also easier to create cryptography.
Therefore, Germans have made enigma machine which have played significant role
win Second World War, which was used to encrypt and decrypt the cipher. As the
war continued, however, allies were able to decrypt the cipher so that they
could receive information about Germany. Therefore, some people believe that
deciphering enigma was one of the main reasons of ally’s victory. As a result
cryptography has played a significant role in the World’s History.
After Second World War, modern cryptology starts with the work
that Claude Shannon have done during Second World War. He established the
robust basis of cryptography by introducing the term called confusion and
diffusion. First, confusion is a skill making the relationship between the key
and the ciphertext complicated. On the other hand, diffusion is a skill
spreading the influence of the plaintext over numerous ciphertexts. After
introduction of two skills there were not significant developments at the beginning
of the 1970s. However, in the mid 1970s there have been two major developments
in the history of cryptography. The
first was the development of Data Encryption Standard by IBM which was used to
develop secure electronic communication. Even though DES itself was not
powerful enough, the alternatives made by using similar method was powerful
enough to guarantee people secure communication. The second major development
was development of new process, distributing cryptographic keys. It has raised
the level of cryptography significantly since it have introduced asymmetric key
algorithm to the world. Asymmetric key algorithm enables decrypting and
encrypting key different. Therefore, we can designate one key of the pair as one
private key and one public key(visible) so that no secure channel is needed for
key exchange. So long as the private key stays secret, the public key can be
widely known for a very long time without compromising security. In modern
society, this is the ultimate version of the cryptography used in real life
such as digital signatures and online purchasing.
Nice touch with the text!
답글삭제Thanks for this excellent detail about cryptography. I find this article a simple but useful guide to learn all about it. I will do refer it to all my students who are facing difficulty in learning about it.
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