Definition of ‘Cryptography’ - Cryptography studies secure communications techniques that allow only the sender and intended recipient of a message to view its contents.
What is cryptography?
Cryptography Definition - Cryptography is about establishing and evaluating protocols that deter third parties from accessing private messages.
The word cryptography comes from the Greek words kryptos and graphein, meaning "hidden" and "writing." Its purpose is to hide information by transforming the original data (called plaintext) into an unreadable format called ciphertext.
The receiver then uses a key to decrypt the ciphertext, turning it into plaintext.
Cryptography permits you to preserve sensitive data or convey it across insecure networks (like the Internet) and hide it from anyone except the purposeful recipient.
For instance, suppose Alice wants to send a private message to Bob.
She could send her message in plaintext, but anyone who intercepts the message can read it. Instead, she encrypts her message with a key known only to her and Bob.
These encrypted messages are called ciphertext. When Bob receives Alice's ciphertext, he decrypts it with his key, turning it back into plaintext that only he can read.
History of Cryptography
The history of cryptography stretches back thousands of years, with a rich and fascinating story that involves secret codes and ciphers, spies, and spies working for other spies.
In ancient Greece, they wrote messages on paper, rolled into a cylinder, and covered with wax.
The soldier entrusted with the message held the stick in his hand while he rode on horseback to deliver the message.
If a spy captured the messenger, he could not read the message without breaking the wax seal. The Greeks also developed a Scytale, a tool used for encryption and decryption of written messages.
It consisted of a cylinder with a strip of parchment wound around it. Words were legible when wound around the cylinder; unwound, they were scrambled.
In World War I and II, cryptography was well understood by both sides of the conflict. However, cryptography became much more complicated in World War II than during World War I due to advances in technology.
The Germans introduced complex cipher machines such as Enigma and Lorenz that encrypted telephone communications.
But ultimately, these machines were broken by teams of people working together, including Polish cryptographers (such as Marian Rejewski) and British codebreakers at Bletch.
In the modern computer age, cryptography is essential to data security.
It's so important that many cryptographers devote their entire careers to keeping data safe from prying eyes.
Additionally, it helps us keep our secrets safe from spies, criminals, and overly enthusiastic government agencies. Also, it allows us to communicate over an open network without worrying about people eavesdropping on our conversations.
What are the three types of cryptography?
There are three main types of cryptography:
Secret key cryptography, also called symmetric-key cryptography, uses the same key for encryption and decryption. When a cryptographer refers to symmetric key cryptography, he means, for example, that both the sender and the receiver use the same secret key for encryption and decryption. It is also called private-key or shared-key cryptography.
Public key cryptography, also called asymmetric-key cryptography, uses a pair of keys (one public and one private) for encryption and decryption. Public key algorithms are considered more secure than secret key algorithms because it's difficult to derive someone's private key from their public key.
Hash Functions is a type of cryptographic function which takes a variable number of input bytes and transforms them into a fixed number of output bytes using a mathematical algorithm. Hash functions are primarily used in digital signatures, message authentication codes (MAC), and other applications where it is necessary to detect accidental or intentional changes to raw data.
What is the difference between cryptography and encryption?
Cryptography and encryption are often used interchangeably, but they are distinct concepts. Cryptography is the science of transforming information into a secure form that unauthorized parties cannot read. This information includes confidentiality, data integrity, entity authentication, and data origin authentication.
However, encryption is converting plaintext to ciphertext (i.e., a process of encoding information).
Decryption is the reverse encryption process; it converts ciphertext back to plaintext.
A cipher (or cypher) is a pair of algorithms that create the encryption and the reversing decryption. The detailed operation is controlled both by the algorithm and in each instance by a "key."
The key is a secret usually shared between the sender and receiver of encrypted messages. However, the third party can only decrypt the message with the authentic key provided.