The confidentiality of information is vital for people, companies and countries. Cryptography develops methods of encoding and decoding information in order to protect it.

Cryptography mainly aims to save information and to transfer messages to recipients safely. Cryptography can change a message into a complicated form by applying several different methods. Encoded information can be resolved only when the receiver applies specific methods to it. Not only does computer cryptography render communication secure but it also gives users secure access to servers.

Nowadays, cryptography is becoming more and more significant, especially now people transfer their personal, commercial, military or political information to each other on internet. It is easy for someone to get personal information through online shopping sites which are very common today. Therefore, credit card information entered into the website is converted into unintelligible characters through an encryption method so that the credit card number can be transmitted to the server securely. Then, the server can easily retrieve the original form of the credit card number using decryption.

The encryption algorithm includes essential elements known as the "key." Protection of the key is always vital for information security.

History of Cryptography

To find the first examples of cryptography one needs to go back more than 4,000 years in history. For instance, in 2000 BCE the ancient Egyptians used hieroglyphs on the gravestones of their kings to describe their achievements when they were alive. Eventually, the system of hieroglyphs grew too complex to understand. Then people began to use it for encoding. Similarly, Chinese people used ideography, which conveys ideas through symbols, to hide the meaning of words.

There are also encoding examples from ancient Mesopotamia that have similar aspects to those used in Egypt. The Roman emperor Julius Caesar used a type of encryption technique called the "Caesar cipher" in which each letter in the plain text is replaced by a letter some fixed number of positions down the alphabet. In the Middle Ages cryptography received a lot of attention from many nations, especially in Europe. In recent years, many different methods have been developed in this field. Therefore, the classical methods are not as useful as they were in the past, especially since the 1970s. Today, more complex mathematical methods have replaced the classical methods of cryptography.

The Arabs were the first to make successful studies of how to decode encrypted messages. Ahmad al-Qalqashandi of Egypt (1355–1418) developed an encryption method which is still used today. This technique is based on a theory of language stability which explores the distribution and frequency of the words in a text. With this method, the frequency of the characters within the encrypted text is compared to the frequency standards in the language; in this way, it is determined what an encoded letter really stands for.

This method is used successfully in decoding messages encrypted by the mono-alphabetic method, which is based on sliding or replacement of a letter by another one.

In 1931, the French obtained documents from a German spy which showed the functions of a code named "Enigma" that was going to be used in World War II by the Germans. British mathematicians were then able to decipher the code during the war. Thus, the commands of Hitler could be learned immediately by the Allied Powers. The Allied countries won the war because of their access to the decryption technique. Likewise, the American army gained victory over the Japanese in the Pacific War in the 1940s because American decryption experts, along with their British and Dutch colleagues, were able to decode the system called JN-25 which was being used by the Japanese army.

Technological developments in computer science have enabled us to decode even previously unbreakable ciphers. For instance, an encrypted message which was created in 1977 and which, it was thought could be decoded only 40 quadrillion years later with the help of an algorithm that analyses the known large numbers into their factors, was actually decoded seventeen years later in 1994.

Classical and modern cryptography

Cryptographic methods are divided into two categories: classical and modern. In the classical method, encoding can be done by consistent replacement of a letter by another letter in the same alphabet. For example, if we replace each letter in the word FOUNTAIN by the third following letter it changes into IRXQWDLQ. It can also be done by replacement of a word with another one or replacement of a character by another character. Of course, the recipient of the message must be the only person who knows the decryption method. In that way, for example, the unintelligible word above can easily be changed back to its original form by replacing each word by the letter three places before it in the alphabet. Such encrypted messages can only be decoded by linguistic analyses or after numerous trials. The classical method was invented hundred of years ago, and it has been used since then. Although this method is so simple that it can even be used manually, computers are the only devices which can have maximum security as well as very long keys and complex algorithms for the modern technique.

The "Spartan cylinder" is another device used in the classical method. A message is written on a piece of paper rolled around a cylinder with a known diameter. The encrypted message is then detached from the cylinder and sent. The only way to decipher the message is to have a cylinder of the same diameter. If the unrolled paper is re-rolled around a decoding cylinder properly, then the original message is obtained. This method is known to have been used by the Spartans around 600 BCE.

One modern method is called Public-Key Cryptography. In this form of cryptography, the key used to encrypt a message differs from the key used to decrypt it. The public key may be widely distributed while the private key is kept secret. Thus, incoming messages are encrypted with the recipient's public key; yet, they cannot be decrypted except with the recipient's private key. Hence, the possessor of the private key is the only one who can decrypt the message and read it.

Conversely, in secret-key cryptography, a single secret key is used for both encryption and decryption. One disadvantage of secret-key cryptography is the distribution of the private key since it is always at risk of being acquired by third parties.

If we look at the universe, we can observe similar cryptographic methods in every creation process. For instance, living cells produce protein by deciphering nucleic acids (DNA, RNA), which include encoded genetic information in ribosomes.

The structure of encoded DNA and encryption in protein synthesis

There is divine wisdom in the encoding of DNA and the transference of these codes to ribosomes in the protein-making process. If we compare DNA molecules, which contain the genetic instructions inside living organisms, to a book, the letters in this book can be symbolized by A, T, and G and C. These symbols represent four molecules which are used in the encoding of the genetic program that shapes the basic form of all living organisms. Each human genome is identified with different sums of those letters. For instance, while the sum of genomic letters is approximately 3 billion in mice and human organisms; it is about 4–5 million in a bacteria. Furthermore, when the genome sequences of two humans are compared, the combination difference between the two appears to be only one percent; nevertheless, no human being is exactly like another in appearance.

There are some interesting distinctions between humans and animals in terms of their genome numbers. The various encoding techniques used in DNA are a basic biological mechanism which can also be considered the mystery behind the genetic diversity in the creation of living organisms. If we compare the genome to a program booklet, we can consider the booklet to be a tiny model of the "Manifest Record" (Imam al-Mubin) mentioned in the Qur'an, in which the future lives of all things and beings, including all the principles governing those lives, and all their deeds and the reasons or causes are kept pre-recorded in this world. The instructions and mechanism used in this encoding program are identical in most living beings. This uniformity shows that they are all created by one Almighty being.

Scientists also observe another kind of encoding which helps transmission of the right message to ribosomes during the protein-making process. The main idea is that unlike the base-pairing of DNA, in messenger RNA (mRNA) the complementary base to adenine is not thymine, as it is in DNA, but rather Uracil, and also that every three nucleotides (a codon) carry information of one amino acid. For example, while codons in DNA appear as "AAT, GCC, GAT, GTA," they appear as "UUA, CGG, CUA, CAU" in mRNA. Here the main goal is not to keep the information safe against the third parties as in normal encryption, but rather to transmit the message properly and preserve the diversity of living beings.

Developments in the area of cryptography do not only provide confidentiality of information, but they also shed light on our understanding of God's wonderful creation in the world of living creatures. All these extensive and essential practices, including the encoding of the information by the four letters of DNA, proper transmission of this encoded information to the cells, and the necessary synthesis in the cell, prove that the All-Knowing and Omnipotent God has great wisdom in all His actions in the Universe.

References

• Protein Synthesis, http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPROTSYn.html.
• Selim Aydın, "Gen Haritası Neler Söylüyor?", Sızıntı, June 2001, no. 269.
• Quantum Cryptography: Privacy Through Uncertainty, October 2002 http://www.csa.com/discoveryguides/crypt/overview.php 1.5.2006.
• Larry Petterson, Bruce S. Davie, Computer Networks: A System Approach, Morgan Kaufmann Publishers, 2000, 568–615.